CN100511746C - Piezoelectric actuator - Google Patents

Abstract

A piezoelectric actuator (1) having a piezoelectric element (2) formed by forming a pair of electrodes on the surface of piezoelectric ceramics as a drive source. The piezoelectric actuator (1) satisfies at least one of the following requirements (a) to (c). (a) The fluctuation amplitude W _C of the apparent dynamic capacitance C[F] with temperature changes is within ±11% within a specific temperature range of -30°C to 80°C, (b) The variation of the displacement L[μm] with temperature The fluctuation width W _L caused by the change is within ±14% within a specific temperature range of -30°C to 80°C. (c) When the apparent dynamic capacitance is set to C[F] and the displacement is set to L[μm], L/ The fluctuation width W _L/C of C with temperature changes is within ±12% within a specific temperature range of -30°C to 80°C.

Description

piezoelectric actuator

technical field

The present invention relates to laminated actuators, piezoelectric transformers, ultrasonic motors, bimorph piezoelectric elements, ultrasonic sonar, piezoelectric ultrasonic vibrators, piezoelectric Piezoelectric actuators for buzzers, piezoelectric speakers, etc.

Background technique

Piezoelectric actuators using piezoelectric ceramic materials are products that convert electrical energy into mechanical energy by using the displacement caused by the reverse piezoelectric effect, and are widely used in the fields of electronics and electromechanics.

Pb(Zr·Ti)O ₃ -based (hereinafter referred to as "PZT-based"), BaTiO ₃ , etc. are known as piezoelectric ceramics used in the piezoelectric actuator. PZT-based piezoelectric ceramics have higher piezoelectric characteristics than other piezoelectric ceramics, and account for most of the piezoelectric ceramics that have been put into practical use. However, since lead oxide (PbO) with a high vapor pressure is contained, there is a problem that the load on the environment is large. On the other hand, although BaTiO ₃ ceramics do not contain lead, they have lower piezoelectric properties than PZT and have a Curie temperature as low as about 120°C, so they cannot be used at high temperatures.

The above-mentioned piezoelectric actuator generally consists of at least a piezoelectric element of piezoelectric ceramics provided with a pair of electrodes, a holding member holding the piezoelectric element, and an adhesive member or spring holding the piezoelectric element on the holding member. member, a lead terminal for applying a voltage to the piezoelectric element, and an electrically insulating member such as resin or silicone oil coated between the pair of electrodes. In the above-mentioned piezoelectric actuators, the piezoelectric element made of piezoelectric ceramics is bonded by bonding, casting, or springs, etc., and therefore receives a mechanical restraint force (preset load) in the state where no voltage is applied. Furthermore, in the piezoelectric actuator described above, when a voltage is applied to the piezoelectric actuator, the piezoelectric element is displaced as the voltage rises, so that the above-mentioned mechanical restraint force increases (load increases).

Therefore, the displacement of the above-mentioned piezoelectric actuator is different from the displacement performance of the piezoelectric element itself due to the preset load and the load increase, and becomes a smaller value.

The operating conditions and driving conditions of the above-mentioned piezoelectric actuator include parameters such as temperature, driving electric field strength, driving waveform, driving frequency, continuous driving or intermittent driving, and the like. The general operating temperature range of the above-mentioned piezoelectric actuator is about -30°C to 80°C at most when it is used in a normal living environment, and about -40°C to 160°C at most when it is used as an automobile part. In addition, the amplitude of the driving electric field strength varies depending on the application of the piezoelectric actuator. It is below 500V/mm in piezoelectric buzzers, ultrasonic sonar, piezoelectric speakers, etc., and in ultrasonic motors, piezoelectric transformers, It is 1000V/mm or less in piezoelectric ultrasonic vibrators, etc., and 3000V/mm or less in laminated actuators. In addition, the drive waveform is a sinusoidal (sinus) wave in the case of resonance driving, and various waveforms such as a sinusoidal wave, a trapezoidal wave, a triangular wave, a rectangular wave, and a pulse wave in other cases. In addition, the driving frequency is 20 kHz or more for ultrasonic motors, ultrasonic sonar, piezoelectric ultrasonic vibrators, and the like, and less than 20 kHz for others.

The driving methods of the above-mentioned piezoelectric actuators can be classified into: (1) constant voltage driving method in which displacement is controlled by using voltage as a parameter, (2) constant energy driving method in which displacement is controlled by injecting energy as a parameter , and (3) a constant charge driving method in which the displacement is controlled by using the injected charge as a parameter for driving.

Here, the relationship between each driving method and the displacement of the piezoelectric actuator will be described.

The driving method of the piezoelectric actuator using the above-mentioned constant voltage driving method has the following feature: the displacement has hysteresis when the applied voltage rises and falls. In this constant voltage driving method, there is a problem that the fluctuation width of the displacement in the operating temperature range is large.

In addition, the driving method of the piezoelectric actuator using the above-mentioned constant energy driving method has the following characteristics: the displacement has hysteresis when the injected energy rises and falls. In this constant energy driving method, the fluctuation width of the displacement in the temperature range used is smaller than that of the above-mentioned constant voltage driving method.

On the other hand, the driving method of the actuator using the constant charge driving method is superior in that it can realize the most precise displacement control because the displacement difference between the rising and falling of the injected charge is almost zero. However, there is a problem that the fluctuation range of the displacement within the operating temperature range is larger than that of the above-mentioned constant voltage driving method and the above-mentioned constant energy driving method.

Therefore, as a method of reducing the fluctuation amplitude of the temperature characteristics of the piezoelectric actuator and the piezoelectric ceramic sensor, for example, the following techniques have been developed.

That is, Japanese Unexamined Patent Publication No. 60-1877 discloses the following piezoelectric body: a piezoelectric unit in which the output displacement of the piezoelectric unit changes in an increasing function with respect to a temperature change, and a piezoelectric unit in which the output displacement changes in a decreasing function when a voltage is applied to the piezoelectric unit. The piezoelectric unit is combined and stacked piezoelectric body.

In addition, JP-A-6-232465 discloses a laminated piezoelectric actuator in which a plurality of piezoelectric ceramic layers having different displacement performances are laminated.

Japanese Unexamined Patent Publication No. 5-284600 discloses a piezoelectric element in which a temperature compensation capacitor and piezoelectric ceramics are electrically connected in series or in parallel.

Japanese Unexamined Patent Application Publication No. 7-79022 discloses a piezoelectric element that generates charges according to pressure. The piezoelectric element is composed of the following materials: piezoelectric layers and dielectric layers are alternately laminated, and the dielectric layer The electrostatic capacitance of the piezoelectric layer is larger than that of the piezoelectric layer, and the temperature coefficient of the dielectric layer has a characteristic opposite to that of the piezoelectric layer.

Japanese Unexamined Patent Application Publication No. 7-79023 discloses a piezoelectric element that generates charges according to pressure, in which a piezoelectric material and a dielectric that has a temperature characteristic opposite to that of the piezoelectric material and whose capacitance changes are combined The materials are mixed and shaped to obtain piezoelectric elements.

In addition, Japanese Patent Laid-Open No. 11-180766 discloses barium titanate-based piezoelectric ceramics. The piezoelectric ceramics have a piezoelectric _d33 constant of 300 pC/N or more measured by a resonance method and have a temperature range of -30°C to 85°C. Composition with small temperature change rate of piezoelectric d ₃₃ .

Japanese Patent Laid-Open No. 2003-128460 discloses a barium titanate-based multilayer piezoelectric element with Ni as an internal electrode, wherein the piezoelectric d ₃₁ calculated from the strain rate of the element when an electric field intensity of 1 kV/mm is applied is Constant temperature change rate is small.

However, fluctuations in the displacement characteristics and the like of the piezoelectric actuator due to temperature changes cannot be adequately resolved in these conventional technologies either.

Contents of the invention

The present invention has been made in view of the above problems, and aims to provide a piezoelectric actuator in which the temperature dependence of displacement can be reduced regardless of the driving method of the piezoelectric actuator.

The first invention is a piezoelectric actuator comprising a piezoelectric element formed by forming a pair of electrodes on the surface of a piezoelectric ceramic as a driving source, wherein a voltage is applied to the piezoelectric actuator, and the electric field strength is When driven under an electric field driving condition with a constant amplitude of 100 V/mm or more, the piezoelectric actuator satisfies at least one of the following requirements (a) to (c).

(a) The fluctuation width WC [%] of the apparent dynamic capacitance C [F] represented by the following formula (1) with temperature changes is within ±11% within a specific temperature range of -30°C to 80°C (where , C[F] is the apparent dynamic capacitance of the piezoelectric actuator, when the piezoelectric actuator is connected in series with the capacitor, and a voltage is applied to the piezoelectric actuator and the capacitor, C[F] can be obtained by using the Calculated by dividing the charge quantity Q[C] accumulated in the capacitor by the voltage V[V] applied to the piezoelectric actuator).

W _C (%)＝[{2×C _max /(C _max +C _min )}—1]×100 (1)

(wherein, C _max represents the maximum value of the apparent dynamic capacitance at -30°C to 80°C, and C _min represents the minimum value of the apparent dynamic capacitance at -30°C to 80°C).

(b) The fluctuation width W _L [%] of the displacement L [μm] represented by the following formula (2) with temperature changes is within ±14% within a specific temperature range of -30°C to 80°C (wherein, L [μm] is the displacement of the piezoelectric actuator).

W _L [%]＝[{2×L _max /(L _max +L _min )}—1]×100 (2)

(wherein, L _max represents the maximum value of displacement at -30°C to 80°C, and Lmin represents the minimum value of displacement at -30°C to 80°C).

(c) The fluctuation width W _L/C (%) of L/C represented by the following formula (3) with temperature changes is within ±12% within a specific temperature range of -30°C to 80°C (wherein, C [F] is the apparent dynamic capacitance of the piezoelectric actuator, L[μm] is the displacement of the piezoelectric actuator, when the piezoelectric actuator is connected in series with the capacitor, and the piezoelectric actuator and the capacitor are externally voltage, the C[F] can be calculated by dividing the voltage V[V] applied to the piezoelectric actuator by the charge quantity Q[C] accumulated in the capacitor).

W _L/C [%]＝[{2×(L/C) _max /((L/C) _max +(L/C) _min )}—1]×100 (3)

(where (L/C) _max represents the maximum value of L/C at -30°C to 80°C, and (L/C) _min represents the minimum value of L/C at -30°C to 80°C).

In addition, the second invention is an electric actuator comprising a piezoelectric element formed by forming a pair of electrodes on the surface of a piezoelectric ceramic as a drive source, wherein a voltage is applied to the piezoelectric actuator, and the electric field intensity When driven under an electric field driving condition with a constant amplitude of 100 V/mm or more, the piezoelectric actuator satisfies at least one of the following requirements (j) to (1).

(j) The fluctuation width W _C [%] of the apparent dynamic capacitance C [F] represented by the following formula (5) with temperature changes is within ±30% within a specific temperature range of -30°C to 160°C ( Among them, C[F] is the apparent dynamic capacitance of the piezoelectric actuator, when the piezoelectric actuator is connected in series with the capacitor, and a voltage is applied to the piezoelectric actuator and the capacitor, C[F] can be obtained by using The charge amount Q[C] accumulated in the capacitor is calculated by dividing the voltage V[V] applied to the piezoelectric actuator).

W _C (%)＝[{2×C _max /(C _max +C _min )}—1]×100 (5)

(wherein, C _max represents the maximum value of the apparent dynamic capacitance at -30°C to 160°C, and C _min represents the minimum value of the apparent dynamic capacitance at -30°C to 160°C).

(k) The fluctuation width W _L [%] of the displacement L [μm] represented by the following formula (6) with temperature changes is within ±14% within a specific temperature range of -30°C to 160°C (wherein, L [μm] is the displacement of the piezoelectric actuator).

W _L [%]=[{2×L _max /(L _max +L _min )}—1]×100 (6)

(wherein, L _max represents the maximum value of displacement at -30°C to 160°C, and L _min represents the minimum value of displacement at -30°C to 160°C).

(1) The fluctuation width W _L/C (%) of L/C represented by the following formula (7) with temperature changes is within ±35% within a specific temperature range of -30°C to 160°C (wherein, C [F] is the apparent dynamic capacitance of the piezoelectric actuator, L [μm] is the displacement of the piezoelectric actuator, when the piezoelectric actuator and the capacitor are connected in series, and the piezoelectric actuator and the capacitor When a voltage is applied, the C[F] can be calculated by dividing the voltage V[V] externally applied to the piezoelectric actuator by the charge quantity Q[C] accumulated in the capacitor).

W _L/C [%]＝[{2×(L/C) _max /((L/C) _max +(L/C) _min )}—1]×100 (7)

(where (L/C) _max represents the maximum value of L/C at -30°C to 160°C, and (L/C) _min represents the minimum value of L/C at -30°C to 160°C).

The piezoelectric actuator of the above-mentioned first invention satisfies at least one of the above-mentioned requirements (a) to (c). That is, in the piezoelectric actuator of the first invention described above, the fluctuation width W _C of the apparent dynamic capacitance C with temperature change, the fluctuation width W _L of the displacement L with temperature change, or the displacement/dynamic At least one of the temperature fluctuation width W _L/C of capacitance (L/C) falls within the above-mentioned specific range when it is within the specific temperature range of -30°C to 80°C.

In addition, the piezoelectric actuator according to the second invention satisfies at least one of the above-mentioned requirements (j) to (1). That is, in the piezoelectric actuator according to the second invention, the fluctuation width W _C of the apparent dynamic capacitance C with temperature change, the fluctuation width W _L of the displacement L with temperature change, or the displacement/dynamic At least one of the temperature-dependent fluctuation width W _L/C of capacitance (L/C) falls within the above-mentioned specific range when it is within the specific temperature range of -30°C to 160°C.

Therefore, the piezoelectric actuators according to the above-mentioned first and second inventions have small variations in displacement due to temperature changes. That is, the above-mentioned piezoelectric actuator can exhibit a substantially constant displacement even when it is used in an environment with severe temperature changes. Therefore, the above-mentioned piezoelectric actuator can also be well used in products used in environments with severe temperature changes, such as automobile parts.

Generally, the driving method of piezoelectric actuators has the following driving methods as mentioned above: (1) constant voltage driving method in which displacement is controlled by using voltage as a parameter, (2) driving is driven by controlling displacement by injecting energy as a parameter The constant energy driving method, and (3) the constant charge driving method using the injected charge as a parameter to control the displacement for driving.

Here, the temperature dependence of the displacement of the piezoelectric actuator will be described for each driving method of the piezoelectric actuator.

First, the displacement (ΔL1) of the piezoelectric actuator driven by a constant voltage is represented by the following formula A1.

ΔL1＝D33×EF×L0 A1

In the formula, D33: dynamic strain amount [m/V], EF: maximum electric field strength [V/m], and L0: length [m] of the piezoelectric ceramic before voltage is applied. In addition, the amount of dynamic strain refers to the piezoelectric ceramics produced in the direction parallel to the direction of the applied voltage when driven with a constant amplitude applied electric field strength of 0 to 3000V/mm and a high voltage in the range of not destroying the insulation. The displacement performance is represented by the following formula A2.

D33＝S/EF＝(ΔL1/L0)/(V/L0) A2

In the formula, S: maximum strain. In addition, D33 has dependence not only on temperature but also on electric field strength.

It can be seen from the above formulas (A1) and (A2) that the displacement (ΔL1) of the piezoelectric actuator is proportional to the product of the dynamic strain D33 dependent on the applied electric field strength and the applied electric field strength.

In addition, energy and charge, apparent dynamic capacitance, and applied voltage have the following relationships of A3 and A4.

W=1/2×C×V ² A3

Q＝C×V A4

In the formula, W: energy [J], C: apparent dynamic capacitance [F], V: applied voltage [V], and Q: charge [C].

Here, when a piezoelectric actuator is generally connected in series with a capacitor and driven with an electric field strength of constant amplitude in the range of 0 to 3000 V/mm without breaking insulation, the apparent dynamic capacitance C[F] is defined as The value obtained by dividing the voltage applied to the actuator by the charge stored in the capacitor. The apparent dynamic capacitance C includes at least a dielectric component of piezoelectric ceramics, a polarization inversion component, charging charges from a polarization rotation component, and leakage current from a DC resistance component of piezoelectric ceramics. Furthermore, the apparent dynamic capacitance C is dependent not only on temperature but also on electric field strength.

Therefore, the displacement (ΔL2) of the piezoelectric actuator in the case of constant energy driving (W: constant) is expressed by the following formula A5, which is related to D33/C ^0.5 and the driving electric field strength (=driving voltage/ The product of L0) is proportional.

ΔL2＝D33×(2×W/C) ^0.5A5

Here, there is a feature that when the apparent dynamic capacitance C fluctuates due to temperature changes, the driving electric field intensity itself also fluctuates according to the above-mentioned expression A3.

In addition, the displacement (ΔL3) of the actuator in the case of constant charge drive (Q: constant) is expressed by the following formula A6, which is related to D33/C and the drive electric field strength (= drive voltage/L0) depending on the drive electric field strength. The product is proportional.

ΔL3＝D33×(Q/C) A6

Here, there is a feature that when C fluctuates due to temperature changes, the applied electric field intensity itself also fluctuates according to the above-mentioned Equation A4.

Therefore, in order to reduce the displacement fluctuation amplitude of the actuator in the operating temperature range, it is preferable that the temperature dependence of D33, D33/C ^0.5 , D33/C, etc. depending on the driving electric field strength is small.

In addition, of course, it is preferable that the absolute values of D33, D33/C ^0.5 , and D33/C, which are displacement properties, be large.

Next, the relationship between the apparent dynamic capacitance and the driving voltage in the case of constant energy driving and constant charge driving will be described.

In the case of constant energy drive (W: constant), the voltage (terminal voltage) applied to the piezoelectric actuator and to the drive circuit is proportional to 1/C ^0.5 as shown in the following formula A7.

V＝(2×W/C) ^0.5 A7

The terminal voltage in the case of constant charge driving (Q: constant) is expressed by the following formula A8, and is proportional to 1/C.

V=Q/C A8

When the terminal voltage fluctuates, in order to ensure the reliability of the withstand voltage of the piezoelectric actuator and the drive circuit, it is necessary to design the upper limit of the terminal voltage. In the design of the actuator, in order to prevent discharge between electrodes or side leakage or insulation damage, the distance between the positive and negative electrodes cannot be reduced. Therefore, the displacement characteristic deteriorates where the lower limit value of the terminal voltage within the temperature range is used. Therefore, in circuit design, there are problems of increasing the size and cost of the circuit element in order to improve the voltage resistance of the circuit element.

Therefore, in order to improve the displacement performance of the actuator and to reduce the size and cost of the drive circuit, it is preferable that the temperature dependence of 1/C ^0.5 and 1/C depending on the drive electric field strength be small.

In addition, if the apparent dynamic capacitance C converges to a constant value, the terminal voltage will also converge to a constant value. Therefore, if the temperature dependence of D33/C ^0.5 is small when the driving electric field strength is constant, the displacement of the actuator in constant energy control The temperature dependence can be reduced. Furthermore, if the temperature dependence of D33/C is small when the driving electric field intensity is constant, the temperature dependence of the displacement of the actuator under constant charge control can be reduced.

In this way, in order to reduce the temperature dependence of the piezoelectric actuator, it is preferable that the dynamic strain D33, the apparent dynamic capacitance C, D33/C ^0.5 , and The fluctuation range of D33/C is small.

In the piezoelectric actuator according to the first invention, as described above, the fluctuation width W _C of the apparent dynamic capacitance C due to temperature change, the fluctuation width W _L of the displacement L due to temperature change, or the displacement At least one of the fluctuation width W _L/ C of the apparent dynamic capacitance (L/C) with temperature changes within a specific temperature range of -30°C to 80°C, within ±11%, within ±14%, respectively and within a smaller range of ±12%.

Furthermore, in the piezoelectric actuator according to the second invention, as described above, the fluctuation width W _C of the apparent dynamic capacitance C according to the temperature change, the temperature fluctuation width W _L of the displacement L according to the temperature change, or At least one of the fluctuation width W _L/C of the above-mentioned displacement/apparent dynamic capacitance (L/C) due to temperature changes is within ±30%, ±14% respectively within the specified temperature range of -30°C to 160°C Within, and within a smaller range within ±35%.

Therefore, the piezoelectric actuators of the above-mentioned first invention and the second invention are independent of driving methods such as constant voltage driving, constant energy driving, and constant charge driving, and the temperature dependence of displacement is small. That is, even if the operating temperature changes, substantially equal displacement characteristics can be exhibited.

As described above, according to the present invention, it is possible to provide a piezoelectric actuator in which the temperature dependence of displacement can be reduced regardless of the driving method of the piezoelectric actuator.

Description of drawings

FIG. 1 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Example 1. FIG.

FIG. 2 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Example 1. FIG.

3 is a graph showing the temperature dependence of displacement/apparent dynamic capacitance of the piezoelectric actuator of Example 1. FIG.

4 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Example 2. FIG.

FIG. 5 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Example 2. FIG.

6 is a graph showing the temperature dependence of displacement/apparent dynamic capacitance of the piezoelectric actuator of Example 2. FIG.

7 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Example 3. FIG.

FIG. 8 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Example 3. FIG.

9 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Example 3. FIG.

10 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Example 4. FIG.

11 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Example 4. FIG.

12 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Example 4. FIG.

13 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Example 5. FIG.

14 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Example 5. FIG.

15 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Example 5. FIG.

16 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 1. FIG.

17 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Comparative Example 1. FIG.

18 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 1. FIG.

19 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 2. FIG.

20 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Comparative Example 2. FIG.

21 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 2. FIG.

22 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 3. FIG.

23 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Comparative Example 3. FIG.

24 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 3. FIG.

25 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 4. FIG.

26 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Comparative Example 4. FIG.

27 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 4. FIG.

28 is a graph showing the temperature dependence of the apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 5. FIG.

29 is a graph showing the temperature dependence of the displacement of the piezoelectric actuator of Comparative Example 5. FIG.

30 is a graph showing the temperature dependence of the displacement/apparent dynamic capacitance of the piezoelectric actuator of Comparative Example 5. FIG.

31 is a graph showing the apparent dynamic capacitance of the piezoelectric actuator (Example 1) and the temperature dependence of the dynamic capacitance in Example 6. FIG.

32 is a graph showing the apparent dynamic capacitance of the piezoelectric actuator (Example 4) and the temperature dependence of the dynamic capacitance in Example 6. FIG.

33 is a graph showing the apparent dynamic capacitance and the temperature dependence of the dynamic capacitance of the piezoelectric actuator (Comparative Example 1) according to Example 6. FIG.

34 is a graph showing the relationship between the electrode strength amplitude and the dynamic strain at a temperature of 20° C. of each piezoelectric actuator obtained in Examples 1 to 5 in Example 7. FIG.

Fig. 35 shows the measured values of the temperature characteristics of _d31 of the veneer produced in Example 5 in Example 8, and the dynamic strain at the driving electric field strength of 1000 to 2000 V/mm shown in Example 5, respectively expressed as Graph of the results normalized to the value at 20°C.

Fig. 36 is an explanatory diagram showing an example of the configuration of the piezoelectric actuator of the present invention.

37 is a schematic explanatory diagram showing the configuration of the piezoelectric actuator of the first embodiment.

38 is an explanatory view showing the configuration of the piezoelectric element of the first embodiment.

FIG. 39 is an explanatory view showing the configuration of a piezoelectric element (single plate) composed of a single piezoelectric ceramic in Example 1. FIG.

40 is an explanatory diagram showing a state in which piezoelectric elements (single plates) and internal electrode plates are stacked in Example 1. FIG.

Detailed ways

Hereinafter, embodiments of the present invention will be described.

The piezoelectric actuator of the above-mentioned first invention satisfies the above-mentioned requirements (a) to (c).

In the above requirement (a), if the apparent dynamic capacitance of the piezoelectric actuator is C[F], the fluctuation width WC [% of the apparent dynamic capacitance according to the temperature change expressed by the following formula (1) ] within the specified temperature range of -30°C to 80°C within ±11%.

W _C (%)＝[{2×C _max /(C _max +C _min )}—1]×100 (1)

In the above-mentioned requirement (a), when the above-mentioned piezoelectric actuator is connected in series with a capacitor set at, for example, a temperature of 25°C, and a voltage is applied to the above-mentioned piezoelectric actuator and the above-mentioned capacitor, the above-mentioned apparent dynamic capacitance can be obtained by using the above-mentioned The amount of charge Q[C] accumulated in the capacitor is calculated by dividing the voltage V[V] externally applied to the piezoelectric actuator.

In the above requirement (b), if the displacement of the piezoelectric actuator is L [μm], the fluctuation width W _L of the displacement L according to the temperature change expressed by the following formula (2) is -30°C to 80°C within ±14% over the specified temperature range.

W _L [%]＝[{2×L _max /(L _max +L _min )}—1]×100 (2)

In addition, in the above requirement (c), when the apparent dynamic capacitance of the piezoelectric actuator is C[F] and the displacement of the piezoelectric actuator is L[μm], then the following formula (3) The fluctuation width W _L/ C of L/C according to the temperature change is within ±12% within a specific temperature range of -30°C to 80°C.

W _L/C [%]＝[{2×(L/C) _max /((L/C) _max +(L/C) _min )}—1]×100 (3)

In the above-mentioned requirement (c), when the above-mentioned piezoelectric actuator is connected in series with a capacitor set at a temperature of 25°C, and a voltage is applied to the above-mentioned piezoelectric actuator and the above-mentioned capacitor, the above-mentioned apparent dynamic capacitance can be obtained by using the above-mentioned The amount of charge Q[C] accumulated in the capacitor is calculated by dividing the voltage V[V] externally applied to the piezoelectric actuator.

When the above-mentioned piezoelectric actuator does not satisfy any of the above-mentioned requirements (a) to (c), that is, at -30°C to 80°C, the above-mentioned fluctuation width W _C deviates from the range within ±11%, and the above-mentioned fluctuation When the amplitude W _L deviates from the range within ±14%, and the above-mentioned fluctuation amplitude W _L/C deviates from the range within ±12%, the temperature dependence of the above-mentioned piezoelectric actuator may occur when the temperature is -30°C to 80°C increase.

The above-mentioned piezoelectric actuator preferably satisfies both the above-mentioned requirement (a) and the above-mentioned requirement (b).

In this case, the temperature dependence of the above-mentioned piezoelectric actuator can be further reduced.

In addition, the piezoelectric actuator preferably satisfies all of the above-mentioned requirements (a) to (c).

In this case, the temperature dependence of the above-mentioned piezoelectric actuator can be further reduced.

In addition, in the above-mentioned piezoelectric actuator, it is preferable that the above-mentioned fluctuation width WC [%] of the dynamic capacitance due to temperature change is within ±12% within a specific temperature range of -40°C to 80°C.

In addition, it is preferable that the above-mentioned fluctuation width WL of the above-mentioned displacement L due to a temperature change is within ±14% within a specific temperature range of -40°C to 80°C.

In addition, it is preferable that the above-mentioned fluctuation width W _L/C of L/C due to temperature change is within ±13% within a specific temperature range of -40°C to 80°C.

In this way, in the temperature range of -40°C to 80°C, when the above-mentioned fluctuation width W _C , fluctuation width W _L , and fluctuation width W _L/C are within the above-mentioned specified ranges, even at the specified temperature range of -40°C to 80°C The temperature dependence of the displacement of the above-mentioned piezo actuator can also be reduced in the temperature range.

The piezoelectric actuator described above preferably satisfies the following requirement (d).

(d) If the above-mentioned apparent dynamic capacitance is C[F], and the displacement of the above-mentioned piezoelectric actuator is L[μm], then the fluctuation of L/C ^0.5 according to the temperature change represented by the following formula (4) Width W _L/C ^0.5 is within ±12% within a specific temperature range of -30°C to 80°C (wherein, L/C ^0.5 is the displacement L[μm] of the above-mentioned piezoelectric actuator and the above-mentioned apparent dynamic capacitance C[ F] square root ratio).

W _L/C ^0.5 (%)＝[{2×(L/C ^0.5 ) _max /((L/C ^0.5 ) _max +(L/C ^0.5 ) _min )}—1]×100

(4)

(In the formula, (L/C ^0.5 ) _max represents the maximum value of L/C ^0.5 at a temperature of -30°C to 80°C, and (L/C ^0.5 ) _min represents the L/C at a temperature of -30°C to 80°C C ^0.5 minimum).

When the above piezoelectric actuator does not meet the above requirement (d), that is, the fluctuation width W L/C ^0.5 of L _/C ^0.5 with temperature changes exceeds ±12% within the specified temperature range of -30°C to 80°C In this case, the temperature dependence of the displacement of the above-mentioned piezoelectric actuator may increase.

In addition, it is preferable that the fluctuation width W L/C ^0.5 of _L/C ^0.5 due to a temperature change is within ±12% within a specific temperature range of -40°C to 80°C.

In this case, the temperature dependence of the displacement of the piezoelectric actuator can be reduced even in the temperature range of -40°C to 80°C.

The piezoelectric actuator described above preferably satisfies the following requirement (e).

(e) The amount of dynamic strain calculated by dividing the strain of the above-mentioned piezoelectric actuator in the direction of the applied electric field by the strength of the electric field is 250 pm/V or more in the specified temperature range of -30°C to 80°C.

When the above-mentioned piezoelectric actuator does not satisfy the above-mentioned requirement (e), that is, if the above-mentioned dynamic strain is less than 250pm/V in the specified temperature range of -30°C to 80°C, the displacement of the above-mentioned piezoelectric actuator may decrease. Small.

In addition, the above-mentioned dynamic strain amount is preferably 250 pm/V or more in a specific temperature range of -40°C to 80°C.

In this case, the displacement of the piezoelectric actuator can also be increased in the temperature range of -40°C to 80°C.

Next, the piezoelectric actuator described above preferably satisfies the following requirement (f).

(f) The above-mentioned fluctuation width WC [%] of the above-mentioned apparent dynamic capacitance C due to temperature change is within ±35% within a specific temperature range of -30°C to 160°C.

In addition, the piezoelectric actuator described above preferably satisfies the following requirement (g).

(g) The above-mentioned fluctuation width WL of the displacement L of the above-mentioned piezoelectric actuator due to temperature changes is within ±14% within a specific temperature range of -30°C to 160°C.

In addition, the piezoelectric actuator described above preferably satisfies the following requirement (h).

(h) If the apparent dynamic capacitance is set to C[F], and the displacement of the piezoelectric actuator is set to L[μm], then the above-mentioned fluctuation amplitude W _L/C generated by the change of L/C with temperature is at -30°C Within the specified temperature range of ~160°C, it is within ±35%.

In addition, the piezoelectric actuator described above preferably satisfies the following requirement (i).

(i) If the apparent dynamic capacitance is set to C[F], and the displacement of the above-mentioned piezoelectric actuator is set to L[μm], then the above-mentioned fluctuation width W L/C ^0.5 caused by the temperature change of _L/C ^0.5 is - Within the specified temperature range of 30°C to 160°C, it is within ±20%.

When the piezoelectric actuator satisfies any one or more of the requirements (f) to (i) above, the temperature dependence of the piezoelectric actuator can be further improved. That is, in this case, the temperature dependence of the displacement of the piezoelectric actuator can be reduced in a wider temperature range of -30°C to 160°C.

Next, in the above-mentioned second invention, the piezoelectric actuator satisfies the above-mentioned requirements (j) to (1).

In the above requirement (j), if the apparent dynamic capacitance of the piezoelectric actuator is C[F], the fluctuation width W _C of the apparent dynamic capacitance according to the temperature change represented by the following formula (5) [ %] is within ±30% within a specific temperature range of -30°C to 160°C.

W _C (%)＝[{2×C _max /(C _max +C _min )}—1]×100 (5)

(wherein, C _max represents the maximum value of the apparent dynamic capacitance at -30°C to 160°C, and C _min represents the minimum value of the apparent dynamic capacitance at -30°C to 160°C).

In the above-mentioned requirement (j), when the above-mentioned piezoelectric actuator is connected in series with a capacitor set at a temperature of 25°C, and a voltage is applied to the above-mentioned piezoelectric actuator and the above-mentioned capacitor, the above-mentioned apparent dynamic capacitance can be obtained by using the above-mentioned The amount of charge Q[C] accumulated in the capacitor is calculated by dividing the voltage V[V] externally applied to the piezoelectric actuator.

In the above-mentioned requirement (k), if the displacement of the above-mentioned piezoelectric actuator is L [μm], the fluctuation width W _L of the displacement L expressed by the following formula (6) with the temperature change is in the range of -30°C to 160°C °C within the specified temperature range within ±14%.

W _L [%]=[{2×L _max /(L _max +L _min )}—1]×100 (6)

(In the formula, L _max represents the maximum value of the displacement at -30°C to 160°C, and Lmin represents the minimum value of the displacement at -30°C to 160°C).

In the above requirement (1), if the apparent dynamic capacitance of the piezoelectric actuator is C[F] and the displacement of the piezoelectric actuator is L[μm], then L expressed by the following formula (7) The fluctuation width W _L/C of /C due to temperature change is within ±35% within a specific temperature range of -30°C to 160°C.

W _L/C [%]＝[{2×(L/C) _max /((L/C) _max +(L/C) _min )}—1]×100 (7)

(In the formula, (L/C) _max represents the maximum value of L/C at -30°C to 160°C, and (L/C) _min represents the minimum value of L/C at -30°C to 160°C).

In the above-mentioned requirement (1), when the above-mentioned piezoelectric actuator is connected in series with a capacitor set at, for example, a temperature of 25°C, and a voltage is applied to the above-mentioned piezoelectric actuator and the above-mentioned capacitor, the above-mentioned apparent dynamic capacitance can be obtained by using the above-mentioned The amount of charge Q[C] accumulated in the capacitor is calculated by dividing the voltage V[V] externally applied to the piezoelectric actuator.

When the above-mentioned piezoelectric actuator does not satisfy any one of the above-mentioned requirements (j) to (1), that is, when the temperature is -30°C to 160°C, the above-mentioned fluctuation width W _C deviates from the range within ±30%, Temperature dependence of the above-mentioned piezoelectric actuator at a temperature of -30°C to 160°C when the above-mentioned fluctuation width W _L is within the range of ±14% and the above-mentioned fluctuation width W _L/C is within the range of ±35% It is possible to increase.

The above-mentioned piezoelectric actuator preferably satisfies both the above-mentioned requirement (j) and the above-mentioned requirement (k).

In this case, the temperature dependence of the above-mentioned piezoelectric actuator can be further reduced.

The piezoelectric actuator described above preferably satisfies all of the above-mentioned requirements (j) to (1).

In this case, the temperature dependence of the above-mentioned piezoelectric actuator can be further reduced.

In addition, in the above-mentioned piezoelectric actuator, it is preferable that the above-mentioned fluctuation width W _C [%] of the apparent dynamic capacitance according to the temperature change is within ±35% within a specific temperature range of -40°C to 160°C.

In addition, it is preferable that the temperature-dependent fluctuation width W _L of the displacement L is within ±14% within a specific temperature range of -40°C to 160°C.

In addition, it is preferable that the above-mentioned fluctuation width W _L/C of L/C due to a temperature change is within ±35% within a specific temperature range of -40°C to 160°C.

In this way, in the temperature range of -40°C to 160°C, if the above-mentioned fluctuation width W _C , fluctuation width W _L , and fluctuation width W _L/C are within the above-mentioned specified ranges, even at the temperature range of -40°C to 160°C The temperature dependence of the displacement of the above-mentioned piezoelectric actuator can also be reduced in the temperature range.

The piezoelectric actuator described above preferably satisfies the following requirement (m).

(m) If the above-mentioned apparent dynamic capacitance is C[F], and the displacement of the above-mentioned piezoelectric actuator is L[μm], the fluctuation of L/C ^0.5 according to the temperature change represented by the following formula (8) Width W _L/C ^0.5 is within ±20% within a specific temperature range of -30°C to 160°C.

W _L/C ^0.5 (%)＝[{2×(L/C ^0.5 ) _max /((L/C ^0.5 ) _max +(L/C ^0.5 ) _min )}—1]×100 (8)

(In the formula, (L/C ^0.5 ) _max represents the maximum value of L/C ^0.5 within the specific temperature range of -30°C to 160°C, and (L/C ^0.5 ) _min represents the specific temperature range of -30°C to 160°C L/C ^0.5 minimum over temperature range).

When the above piezoelectric actuator does not satisfy the above requirement (m), that is, the fluctuation width W L/C ^0.5 of L/ _C ^0.5 with temperature changes exceeds ±20% within the specified temperature range of -30°C to 160°C In this case, the temperature dependence of the displacement of the above-mentioned piezoelectric actuator may increase.

In addition, it is preferable that the fluctuation width W L/C ^0.5 of _L/C ^0.5 due to temperature change is within ±20% within a specific temperature range of -40°C to 160°C.

In this case, even in the temperature range of -40°C to 160°C, the temperature dependence of the displacement of the piezoelectric actuator can be reduced.

The piezoelectric actuator described above preferably satisfies the following requirement (n).

(n) The amount of dynamic strain calculated by dividing the strain of the piezoelectric actuator in the direction of the applied electric field by the electric field strength is 250 pm/V or more in the specified temperature range of -30°C to 160°C.

When the above-mentioned piezoelectric actuator does not satisfy the above-mentioned requirement (n), that is, if the above-mentioned dynamic strain is less than 250pm/V in a specific temperature range of -30°C to 160°C, the displacement of the above-mentioned piezoelectric actuator may decrease. Small.

In addition, it is preferable that the above-mentioned dynamic strain amount is 250 pm/V or more in the temperature range of -40°C to 160°C.

In this case, even in the temperature range of -40°C to 160°C, the displacement of the piezoelectric actuator can be increased.

In addition, in the above-mentioned first and second inventions, the piezoelectric actuator includes, as a driving source, a piezoelectric element constituted by forming a pair of electrodes on the surface of piezoelectric ceramics.

The above piezoelectric ceramic is preferably composed of an alkali metal-containing piezoelectric ceramic containing at least one selected from Li, K, and Na.

In this case, the leakage current increases even more when driven in a high-temperature environment with a temperature of 80°C or higher, and the fluctuation width of the above-mentioned "apparent dynamic capacitance" at a temperature of 80°C or higher is also larger than that of "" Electrostatic capacitance" and "dynamic capacitance" fluctuate even more. Therefore, in this case, the above-mentioned requirements (a) and/or (c) of the above-mentioned first invention, the above-mentioned requirements (j) and And/or (1), for example, the above-mentioned effect of reducing the temperature dependence of displacement in constant energy driving and constant charge driving can be exhibited more remarkably.

In addition, the piezoelectric ceramic preferably has a specific resistance of 1×10 ⁶ Ω·m or more in the entire operating temperature range of the piezoelectric actuator (for example, temperature -30°C to 160°C). In this case, the destruction of the above-mentioned piezoelectric ceramics due to resistance heating can be prevented. More preferably, the piezoelectric ceramic has a specific resistance of 1×10 ⁸ Ω·m or more within the temperature range in which the piezoelectric actuator is used. In this case, the life of the above-mentioned piezoelectric actuator can be further extended.

In addition, the piezoelectric ceramics described above preferably do not contain lead.

In this case, it is possible to manufacture the above-mentioned piezoelectric actuator that does not contain lead, which has a large environmental load. That is, the environmental safety of the piezoelectric actuator described above can be improved.

In addition, the above-mentioned piezoelectric ceramic is preferably: formed by the general formula {Li _x (K _1-y Na _y ) _1-x }{Nb _{1-z- w} Ta _z Sb _w }O ₃ (wherein, 0≤x≤ 0.2, 0 ≤ y ≤ 1, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.2, x + z + w > 0) represented by isotropic perovskite-type compounds as the main phase of the polycrystal, and at the same time composed of the It consists of a crystal-oriented piezoelectric ceramic in which a specific crystal plane of each crystal grain of a polycrystal is oriented.

In this case, a piezoelectric actuator satisfying the above requirements (a) to (i) and a piezoelectric actuator satisfying the above requirements (j) to (n) can be easily realized.

The above-mentioned crystal-oriented piezoelectric ceramic is basically composed of potassium sodium niobate (K _1-y Na _y NbO ₃ ), one of the isotropic perovskite-type compounds, and a part of the A-site elements (K, Na) is A predetermined amount of Li is substituted, and/or a part of the B-site element (Nb) is substituted by a predetermined amount of Ta and/or Sb. In the above general formula, "x+z+w>0" means that at least one of Li, Ta, and Sb may be contained as a substituting element.

In addition, in the above general formula, "y" represents the ratio of K to Na contained in the crystal-oriented piezoelectric ceramic. In the crystal-oriented piezoelectric ceramic of the present invention, at least one of K and Na may be contained as the A-site element. That is, the ratio y of K to Na is not particularly limited, and can take any value between 0 and 1. In order to obtain high displacement characteristics, the value of y is preferably from 0.05 to 0.75, more preferably from 0.20 to 0.70, still more preferably from 0.35 to 0.65, still more preferably from 0.40 to 0.60, and still more preferably from 0.42 to 0.60.

"x" represents the replacement amount of K and/or Na of the A-site element replaced by Li. When a part of K and/or Na is substituted by Li, effects such as improvement of piezoelectric characteristics, increase of Curie temperature, and/or acceleration of densification can be obtained. The value of X is specifically preferably 0 or more and 0.2 or less. When the value of x exceeds 0.2, the displacement characteristic is deteriorated, which is not preferable. The x value is preferably from 0 to 0.15, and more preferably from 0 to 0.10.

"z" represents the amount of substitution of Ta for Nb of the B-site element. When a part of Nb is substituted by Ta, effects such as improvement of displacement characteristics can be obtained. The value of z is specifically preferably from 0 to 0.4. When the z value exceeds 0.4, the Curie temperature decreases, and it is difficult to use as a piezoelectric material for home appliances and automobiles, so it is not preferable. The z value is preferably from 0 to 0.35, and more preferably from 0 to 0.30.

Also, "w" represents the amount of substitution of Nb in which Sb is substituted for the B-site element. When a part of Nb is substituted by Sb, effects such as improvement of displacement characteristics can be obtained. The value of w is specifically preferably 0 or more and 0.2 or less. When the w value exceeds 0.2, the displacement characteristics and/or the Curie temperature are lowered, which is not preferable. The w value is preferably from 0 to 0.15.

In addition, in the above-mentioned crystal-oriented piezoelectric ceramics, as the temperature decreases from high temperature to low temperature, the crystal phase changes from cubic crystal to tetragonal crystal (the first crystal phase transition temperature = Curie temperature), and from tetragonal crystal to orthorhombic crystal (second crystal phase). transition temperature), orthorhombic → rhombohedral (third crystal phase transition temperature). In the temperature region higher than the first crystallization phase transition temperature, the displacement characteristic disappears due to cubic crystal formation, and in the temperature region lower than the second crystallization phase transition temperature, it becomes orthorhombic crystallization, displacement and apparent dynamic capacitance temperature Dependency increases. Therefore, it is preferable that the piezoelectric ceramics can be made tetragonal throughout the entire temperature range of use by making the first crystal phase transition temperature higher than the temperature range of use and the second crystal phase transition temperature lower than the temperature range of use.

However, potassium sodium niobate (K _{1- y} Na _y NbO ₃ ), which is a basic constituent of the above-mentioned crystal-oriented piezoelectric ceramics, according to "Journal of American Ceramic Society", USA, 1959, Vol. 42 [ 9] p.438～443, and US Patent No. 2976246 specification, as the temperature drops from high temperature to low temperature, the crystal phase changes from cubic crystal to tetragonal crystal (first crystal phase transition temperature = Curie temperature), tetragonal crystal to orthorhombic crystal (second crystal phase transition temperature), orthorhombic → rhombohedral (third crystal phase transition temperature). In addition, the first crystal phase transition temperature at "y=0.5" is about 420°C, the second crystal phase transition temperature is about 190°C, and the third crystal phase transition temperature is about -150°C. Therefore, the temperature range of the tetragonal crystal is in the range of 190°C to 420°C, which is inconsistent with the operating temperature range of industrial products -40°C to 160°C.

On the other hand, in the above-mentioned crystal-oriented piezoelectric ceramics, for the basic composition of potassium sodium niobate (K _{1 -y} Na _y NbO ₃ ), by changing the amount of Li, Ta, and Sb substituting elements, the first element can be freely changed. The crystal phase transition temperature and the second crystal phase transition temperature.

For y = 0.4 to 0.6 when the piezoelectric characteristic is at its maximum, multiple regression analysis was performed on the amount of substitution of Li, Ta, and Sb and the actual measurement value of the crystallization phase transition temperature. The results are shown in the following formulas B1 and B2. .

From Formula B1 and Formula B2, it is known that the amount of Li substitution has the effect of raising the first crystal phase transition temperature and lowering the second crystal phase transition temperature. In addition, Ta and Sb have the effect of lowering the first crystal phase transition temperature and lowering the second crystal phase transition temperature.

The first crystalline phase transition temperature = (388+9x—5z—17w)±50[°C] (Formula B1)

The second crystalline phase transition temperature = (190—18.9x—3.9z—5.8w)±50[°C] (Formula B2)

The first crystal phase transition temperature is the temperature at which the piezoelectricity completely disappears, and the dynamic capacitance increases rapidly in the vicinity thereof, so it is preferably (the upper limit temperature of the product use environment + 60° C.) or higher. The second crystalline phase transition temperature is only the temperature at which the crystalline phase transitions, and the piezoelectricity does not disappear, so it can be set within a range that does not adversely affect the temperature dependence of displacement or dynamic capacitance, so it is preferably (of the product) The lower limit temperature of the operating environment is below +40°C).

On the other hand, the upper limit temperature of the product's operating environment varies depending on the application, and is 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, etc. The lower limit temperature of the product's use environment is -30°C, -40°C, etc.

Therefore, since the first crystal phase transition temperature represented by the above formula B1 is preferably 120°C or higher, "x", "z", and "w" preferably satisfy (388+9x-5z-17w)+50≥120.

Moreover, since the second crystal phase transition temperature shown in formula B2 is preferably below 10°C, "x", "z", and "w" preferably satisfy (190—18.9x—3.9z—5.8w)—50≦10 .

That is, in the above crystal-oriented piezoelectric ceramic, x, y and z in the above general formula: {Li _x (K _1-y Na _y ) _1-x }{Nb _{1 -zw} Ta _z Sb _w }O ₃ are preferably The relationship of the following formula (9) and formula (10) is satisfied.

9x—5z—17w≥—318 (9)

—18.9x—3.9z—5.8w≤—130 (10)

In addition, the above-mentioned crystal-oriented piezoelectric ceramics may be composed only of the isotropic perovskite compound (first KNN-based compound) represented by the above general formula, or may be actively added or substituted by other elements.

In the case of the former, it is preferable to consist only of the first KNN-based compound, but as long as the isotropic perovskite crystal structure can be maintained and there is no adverse effect on various properties such as sintering characteristics and piezoelectric characteristics, it may also contain other elements or other phases. Especially in the raw materials used to manufacture the above-mentioned crystal-oriented piezoelectric ceramics, the mixing of impurities contained in commercially available commercial raw materials with a purity of 99% to 99.9% is unavoidable. For example, Nb ₂ O ₅ , one of the raw materials of the above-mentioned crystal-oriented piezoelectric ceramics, sometimes contains less than 0.1 wt% of Ta and less than 0.15 wt% of F as impurities derived from raw material ores or production methods. In addition, as will be described in Example 1 described later, when Bi is used in the manufacturing process, its contamination is unavoidable.

In the latter case, for example, by adding Mn, it can reduce the temperature dependence of the apparent dynamic capacitance and increase the displacement effect, and it also has the effect of reducing the dielectric loss tanδ and improving the mechanical quality coefficient Qm. Therefore, as a resonance-driven type Actuating components can get ideal characteristics.

In addition, in the above-mentioned crystal-oriented piezoelectric ceramics, specific crystal planes of each crystal grain constituting the polycrystal having the isotropic perovskite-type compound represented by the above-mentioned general formula as a main phase are in an oriented state. Among them, the specific crystal plane oriented in the crystal grains is preferably a pseudo-cubic {100} plane.

In addition, the so-called "quasi-cubic {HKL}" means that the structure of the isotropic perovskite compound is usually tetragonal, orthorhombic, trigonal, etc., which are slightly deformed compared with the cubic crystal, but because the deformation is only A little bit, so it is regarded as a cubic crystal and expressed by Miller index.

In this case, the displacement of the piezoelectric actuator can be further increased, and at the same time, the temperature dependence of the apparent dynamic capacitance can be reduced.

In addition, when plane-orienting a pseudo-cubic {100} plane, the degree of plane orientation can be represented by an average orientation degree F(HKL) based on the Lotgering method represented by the following Mathematical Formula 1.

Mathematical formula 1

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; HKL</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\frac{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; ,</span>}\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; HKL</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;I</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; hkl</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; ,</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; HKL</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; hkl</span>}<span\; class="notranslate">\; )</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; ,</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; HKL</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; hkl</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \%</span><span\; class="notranslate">\; )</span>$

In addition, in Mathematical Formula 1, ΣI(hk1) is the sum of the X-ray diffraction intensities of all crystal planes (hk1) measured for crystal-oriented piezoelectric ceramics, and ΣI0(hk1) is the sum of The sum of the X-ray diffraction intensities of all crystal planes (hk1) measured for non-oriented ceramics of the same composition. Also, Σ'I(HKL) is the sum of the X-ray diffraction intensities of crystallographically equivalent specific crystal planes (HKL) measured for the crystal-oriented piezoelectric ceramic. Σ'I ₀ (HKL) is the sum of the X-ray diffraction intensities of crystallographically equivalent specific crystal planes (HKL) measured for non-oriented ceramics having the same composition as the crystal-oriented piezoelectric ceramics.

Therefore, when each crystal grain constituting the polycrystal is non-oriented, the average degree of orientation F(HKL) is 0%. On the other hand, when the (HKL) planes of all crystal grains constituting the polycrystal are oriented parallel to the measurement plane, the average orientation degree F(HKL) is 100%.

Generally, the higher the ratio of oriented crystal grains, the higher the properties can be obtained. For example, when plane-orienting a specific crystal plane, in order to obtain high piezoelectric properties, etc., the average orientation degree F(HKL) based on the Lotgering method represented by the above formula 1 is preferably 30 % or more, more preferably 50% or more, still more preferably 70% or more. In addition, the specific crystal plane to be oriented is preferably a plane perpendicular to the polarization axis. For example, when the crystal system of the perovskite-type compound is a tetragonal crystal, the specific crystal plane for orientation is preferably a pseudo-cubic {100} plane.

That is, it is preferable that the above-mentioned crystal-oriented piezoelectric ceramic has a degree of orientation of a pseudo-cubic {100} plane obtained by the Lautergeldin method of 30% or more, and a crystal system of a square crystal system in a temperature range of 10°C to 160°C. crystal (claim 22).

In addition, when a specific crystal plane is axially oriented, the degree of orientation cannot be defined by the same degree of orientation (equation 1) as that of plane orientation. However, when performing X-ray diffraction on a plane perpendicular to the orientation axis, the degree of axis orientation can be represented by the average orientation degree (axis orientation degree) of the Lotgering method involving (HKL) diffraction. In addition, the degree of axial orientation of a molded body in which a specific crystal plane is substantially completely axially oriented has the same degree of axial orientation as that measured for a molded body in which a specific crystal plane is substantially completely plane oriented.

Next, the characteristics of piezoelectric actuators using the above crystal-oriented piezoelectric ceramics will be described.

In the piezoelectric actuator using the above-mentioned crystal-oriented piezoelectric ceramic as a driving source, it is possible to control the electric field strength at an electric field strength of 100 V/mm or more without breaking insulation in a temperature range of -30°C to 160°C. The dynamic strain amount D33 generated under the electric field driving condition with a constant amplitude below is controlled to be 250 pm/V or more. If the composition and process are further optimized, it can be controlled to be more than 300 pm/V, further more than 350 pm/V, further more than 400 pm/V, further more than 450 pm/V, and further more than 500 pm/V.

Also, the fluctuation width of the displacement (=the fluctuation width of the dynamic strain amount) can be controlled to be ±14% or less if the reference value is (maximum value−minimum value)/2. If the composition and process are further optimized, it can be controlled to be less than ±12%, further to be less than ±10%, and further to be less than ±8%.

In addition, in the temperature range of -30°C to 80°C, the fluctuation amplitude of the displacement (= the fluctuation amplitude of the dynamic strain amount) generated under the electric field drive condition with a constant amplitude of the electric field strength of 100V/mm or more is expressed as ( Maximum value-minimum value)/2 is the reference value, and it can be controlled to be ±14% or less. If the composition and process are further optimized, it can be controlled to be below ±12%, further below ±9%, further below ±7%, further below ±5%, and further below ±4%. Therefore, it is possible to obtain an actuator with little temperature dependence of displacement driven by constant voltage.

In addition, in the piezoelectric actuator using the above-mentioned crystal-oriented piezoelectric ceramic as the driving source, in the temperature range of -30°C to 160°C, under the electric field driving condition with a constant amplitude of electric field strength of 100V/mm or more The fluctuation width of the generated apparent dynamic capacitance can be controlled to be ±35% or less if the reference value is (maximum value-minimum value)/2. If the composition and process are further optimized, it can be controlled to be less than ±32%, further to be less than ±30%, and further to be less than ±28%.

In addition, in the temperature range of -30°C to 80°C, if the fluctuation amplitude of the apparent dynamic capacitance generated under the electric field driving condition with a constant amplitude of electric field strength above 100V/mm is (maximum value - minimum value) /2 is the reference value, and it can be controlled to be ±11% or less. If the composition and process are further optimized, it can be controlled to be less than ±9%, further less than ±7%, further less than ±5%, and further less than ±4%. Therefore, in the case of constant charge drive and constant energy drive, an actuator with little temperature dependence of the terminal voltage can be obtained.

In addition, in the piezoelectric actuator using the above-mentioned crystal-oriented piezoelectric ceramic as the driving source, in the temperature range of -30°C to 160°C, under the electric field driving condition with a constant amplitude of electric field strength of 100V/mm or more The amplitude of the resulting displacement/apparent dynamic capacitance fluctuation is given by

(Maximum value-Minimum value)/2 is used as a reference value, and it can be controlled to be ±35% or less. If the composition and process are further optimized, it can be controlled to be less than ±30%, further to be less than ±25%.

In addition, in the temperature range of -30°C to 80°C, if the displacement/apparent dynamic capacitance fluctuation amplitude generated under the electric field driving condition with a constant amplitude of electric field strength above 100V/mm is expressed as (maximum value - minimum value )/2 as a reference value, it can be controlled to be ±12% or less. If the composition and process are further optimized, it can be controlled to be less than ±9%, further to be less than ±7%. Therefore, an actuator with little temperature dependence of displacement in constant charge driving can be obtained.

In addition, in the piezoelectric actuator using the above-mentioned crystal-oriented piezoelectric ceramic as the driving source, in the temperature range of -30°C to 160°C, under the electric field driving condition with a constant amplitude of electric field strength of 100V/mm or more If the fluctuation width of generated displacement/(apparent dynamic capacitance) ^0.5 is based on (maximum value-minimum value)/2, it can be controlled to be ±20% or less. If the composition and process are further optimized, it can be controlled to be below ±15%.

In addition, in the temperature range of -30°C to 80°C, the displacement/(apparent dynamic capacitance) generated under the electric field drive condition with a constant amplitude of electric field strength of 100V/mm or more is ^0.5 if the fluctuation amplitude is (maximum value-minimum value)/2 as the reference value, it can be controlled to be ±12% or less. If the composition and process are further optimized, it can be controlled to be less than ±9%, further to be less than ±7%. Therefore, an actuator with little temperature dependence of displacement during constant energy driving can be obtained.

In addition, all the displacement generating sources of the piezoelectric actuator may be made of the above-mentioned crystal-oriented piezoelectric ceramics, but within the range that does not affect the displacement characteristics of the piezoelectric actuator, the expression expressed by the above general formula (1) may also be Piezoelectric ceramics are combined with other piezoelectric ceramics to form piezoelectric actuators. For example, in the case of a laminated actuator, more than 50% of the volume of the piezoelectric ceramics can be composed of crystal-oriented piezoelectric ceramics represented by the above general formula (1), and the remaining less than 50% can be made of barium titanate-based piezoelectric ceramics. electric ceramics etc.

Next, an actuator in which a piezoelectric ceramic and a semiconductor element with a positive temperature characteristic are connected in parallel will be described.

In the piezoelectric actuator composed of the above-mentioned piezoelectric ceramics, the displacement and apparent dynamics generated under the driving condition of an electric field with a constant amplitude and an electric field strength of 100 V/mm or more in the temperature range of -30°C to 80°C Capacitance, Displacement/Apparent Dynamic Capacitance, Displacement/(Apparent Dynamic Capacitance) ^0.5 has a small fluctuation range, and an actuator with good temperature characteristics can be obtained. However, in the temperature range of -30°C to 160°C, although the fluctuation of the displacement is small, the apparent dynamic capacitance may increase a little.

To investigate the cause, the dynamic capacitance was measured after removing the leakage current component of the piezoelectric actuator. As a result, the dynamic capacitance did not increase even in the temperature range above 80°C. That is, it can be seen that the leakage current of the above-mentioned piezoelectric ceramics greatly increases in a temperature region higher than 80°C. This is because the value of the specific resistance is about 2 orders of magnitude lower than the value at a temperature of 25°C. The specific resistance at a temperature of 25° C. has a value of 10 ¹⁰ Ω·m or more.

From this, it is known that in order to reduce the fluctuation width of the apparent dynamic capacitance in the temperature range of -30°C to 160°C, the resistance is lowered in the temperature range below about 80°C, and the resistance is increased in the high temperature range exceeding about 80°C. A semiconductor element having a positive temperature coefficient of resistance may be electrically connected in parallel to the actuator, and the temperature of the PTC resistor may be substantially equal to the temperature of the piezoelectric element. In this way, when the temperature is below 80°C, a large amount of current flows through the PTC resistor, and when the temperature is above 80°C, almost no current flows through the PTC resistor, so the fluctuation width of the apparent dynamic capacitance of the actuator can be reduced. As a result, in a wide temperature range of -30°C to 160°C, a piezoelectric actuator with small temperature dependence of terminal voltage and small temperature dependence of displacement in constant charge drive and constant energy drive can be obtained.

That is, the above-mentioned piezoelectric actuator preferably includes a PTC resistor having a positive temperature coefficient of resistance, and the PTC resistor is electrically connected in parallel with the above-mentioned piezoelectric ceramic having a negative temperature coefficient of resistance, and at the same time according to the above-mentioned PTC resistor The temperature is arranged in a positional relationship that is substantially equal to the temperature of the piezoelectric ceramic (claim 15).

Here, the substantially equal temperature means that the temperature difference between the piezoelectric ceramic (piezoelectric element) and the PTC resistor when the piezoelectric actuator is driven is within 40°C, more preferably within 30°C, and even more preferably It is within 20°C, more preferably within 10°C.

In addition, the positional relationship of the arrangement includes: when the above-mentioned PTC resistor is arranged in contact with the piezoelectric ceramics, when the PTC resistor is provided between the lead terminals of the piezoelectric actuator, and in a part different from the piezoelectric actuator. That is, when a PTC resistor is placed on the connector, etc.

In addition, the resistance-temperature characteristic of the PTC resistor is preferably a barium titanate-based semiconductor element whose resistance value rises rapidly at a high temperature exceeding about 80°C. That is, the above-mentioned PTC resistor is preferably a barium titanate-based semiconductor, and has a positive temperature coefficient of resistance in a temperature range of 80° C. or higher. (claim 16).

In this case, the insulation of the PTC semiconductor at a temperature of 80° C. or higher is further improved, so that the leakage current flowing in the parallel circuit of the actuator and the PTC element can be reduced. In addition, the barium titanate-based semiconductor whose resistance value rises sharply at 80°C or higher does not contain lead as an additive that shifts the Curie temperature to high temperatures, and therefore does not contain lead as an actuator, so it is more preferable.

Furthermore, when the actuator is an airtight package type, and the semiconductor element is installed inside the airtight package, the insulating resin used in the actuator will be thermally decomposed when used for a long time, and the inside of the airtight package may be consumed. Therefore, a reduction-resistant barium titanate-based semiconductor element whose resistance value does not decrease even in an atmosphere with a low oxygen concentration is preferable.

In addition, if the resistance value of the PTC resistor is low, the voltage applied to the actuator is also reduced, so the resistance value of the PTC resistor is preferably sufficiently larger than the impedance of the piezoelectric actuator when the piezoelectric actuator is driven.

In addition, it does not matter whether the PTC resistor itself generates heat or not due to the drive of the piezoelectric actuator. In the case of self-heating, for example, by arranging a PTC resistor at a position where heat is easily transferred to the piezoelectric element, it can function as a temperature heater and increase the lower limit temperature of the actuator. That is, by narrowing the operating temperature range, it is possible to substantially reduce the fluctuation width of the apparent dynamic capacitance of the actuator and the like. In particular, barium titanate-based semiconductor elements are suitable for PTC resistors because they are constant-temperature heaters whose resistance value rises rapidly at the Curie temperature.

On the other hand, when self-heating is not involved, the current flowing in the parallel circuit of the actuator and the semiconductor element is reduced, so that the increase in circuit cost can be suppressed.

In addition, it is preferable that the piezoelectric actuator has a laminated piezoelectric ceramic formed by laminating a plurality of piezoelectric ceramics as the piezoelectric ceramic and is used for a fuel injection valve (claim 17).

In this case, the characteristics of the above-mentioned piezoelectric actuator can be brought into full play.

Next, an example of the configuration of the piezoelectric actuator of the present invention will be described using FIG. 36 .

As shown in the figure, the piezoelectric actuator 1 can be composed of, for example, a piezoelectric element 2 having piezoelectric ceramics, a holding member 4 for holding the piezoelectric element, a cover member 3 for accommodating the piezoelectric element, and a device for transmitting the piezoelectric element. The displacement transmission member 5 constitutes.

As the piezoelectric element 2 , as shown in FIG. 38 described later, for example, a multi-layer piezoelectric element formed by laminating a plurality of piezoelectric ceramics 21 and internal electrodes 22 and 23 alternately can be used.

In addition, as the piezoelectric element, a single-plate piezoelectric element (not shown) configured by sandwiching one piece of piezoelectric ceramic between two internal electrodes can be used.

In addition, a pair of external electrodes 25 and 26 are formed on the side surfaces of the piezoelectric element 2 , and two adjacent internal electrodes 22 and 23 in the piezoelectric element 2 are electrically connected to mutually different external electrodes 25 and 26 .

As shown in FIG. 36 , in the piezoelectric actuator 1 , a transmission member 5 such as a piston is arranged at one end of the piezoelectric element 2 in the stacking direction. A disc spring 55 is arranged between the housing 3 and the transmission member 5 to apply a predetermined load to the piezoelectric element 2 . The transmission member 5 is movable according to the displacement of the piezoelectric element 2 and can transmit the displacement to the outside. In addition, moving through holes 31 and 32 are provided on the housing 3 . Terminals (lead wires) 61 and 62 for supplying electric charge from the outside are inserted into the movable through holes 31 and 32 , and the airtightness inside the housing 3 is maintained by the gaskets 31 and 32 . The terminals 61 and 62 are electrically connected to the external terminals 25 and 26 provided on the piezoelectric element 2 .

As shown in FIG. 36 , an O-ring 35 is disposed between the piston member 5 and the housing 3 , and the piston member 5 is stretchable and movable while maintaining the airtightness inside the housing 3 .

The piezoelectric actuator described above can be used, for example, in a fuel injection valve or the like. In addition, examples of the above-mentioned piezoelectric actuators include laminated actuators, piezoelectric transformers, ultrasonic motors, bimorph piezoelectric elements, ultrasonic sonars, piezoelectric ultrasonic vibrators, piezoelectric buzzers, piezoelectric speakers, and the like.

(Example 1)

Next, examples of the present invention will be described.

In this example, a piezoelectric element including piezoelectric ceramics was produced, and a piezoelectric actuator was produced using this piezoelectric element.

In this example, as a model of the piezoelectric actuator, a piezoelectric actuator 11 using a jig 8 is fabricated as shown in FIG. 37 .

That is, the piezoelectric actuator 11 of this example has a multilayer piezoelectric element 2 using piezoelectric ceramics as a driving source, and the piezoelectric element 2 is fixed by a jig 8 .

The jig 8 has a housing 81 for accommodating the piezoelectric element 2 , and a piston (connecting member) 82 connected to the piezoelectric element 2 for transmitting the displacement of the piezoelectric element 2 . Piston 82 is connected to guide 83 via disk spring 85 . A base portion 815 is provided inside the housing 81 , and the piezoelectric element 2 is arranged on the base portion 815 . The piezoelectric element 2 arranged on the pedestal portion 815 is fixed by the head portion 821 of the piston 82 . At this time, a preset load can be applied to the piezoelectric element 2 from the disc spring 85 . In addition, the end portion (measurement portion 88 ) on the opposite side of the head portion 821 of the piston 82 can move according to the displacement of the piezoelectric element 2 .

Here, the method of applying the preset load will be described. The preset load can be obtained by the following method: Insert a cylindrical pressure rod (not shown) in the gap between the piston 82 and the press-in bolt 84, and apply it to the guide device 83 with an Amsler type testing machine. correct load. Next, in order to maintain a preset load, the press-in bolts 84 and the cover 81 are fixed in a state where the load is applied. Then, remove the above-mentioned pressing rod.

In addition, in this example, the reason for creating the model of the piezoelectric actuator is to evaluate the temperature characteristic of the displacement of the piezoelectric actuator. By making the shape elongated, the piezoelectric element 2 can be installed inside the constant temperature bath, and the measurement unit 88 can be installed outside the constant temperature bath (=temperature about 25° C.). In the evaluation of the temperature characteristics described later, for the piezoelectric actuator 11 shown in FIG. 37 , the portion below the dotted line was provided inside the constant temperature bath. At this time, in order to prevent heat from moving to the portion above the dotted line in the piezoelectric actuator, a heat insulating material 86 is provided in the piezoelectric actuator.

Such a model of the piezoelectric actuator is functionally equivalent to the piezoelectric actuator shown in FIG. 36 .

In addition, as shown in FIG. 38 , in this example, the piezoelectric element 2 is constituted by a multilayer piezoelectric element in which piezoelectric ceramics 21 and internal electrode plates 22 and 23 are alternately laminated. In addition, alumina plates 245 are arranged on both ends of the piezoelectric element 2 in the stacking direction.

In addition, two external electrodes 25 and 26 are formed on the side surfaces of the piezoelectric element 2 so as to sandwich the piezoelectric element, and the external electrodes 25 and 26 are connected to lead wires 61 and 62 .

In addition, the internal electrode plates 22 and 23 are electrically connected to the external electrodes 25 and 26 such that two adjacent internal electrodes 22 and 23 in the piezoelectric element 2 are respectively connected to the external electrodes 25 and 26 of different potentials.

In addition, in the piezoelectric element 2 of this example, a total of 40 piezoelectric ceramics 21 are stacked, and the number of stacks is omitted in the figure shown in FIG. 38 for the convenience of drawing.

Next, a method of manufacturing the piezoelectric actuator of this example will be described.

First, a piezoelectric element is fabricated as follows.

(1) Synthesis of NaNbO ₃ flake powder

Bi ₂ O ₃ powder, Na ₂ CO ₃ powder, and Nb ₂ O ₅ powder were weighed so as to have a stoichiometric composition of Bi _2.5 Na _3.5 Nb ₅ O ₁₈ , and these were wet-mixed. Next, 50 wt % of NaCl was added as a flux to this raw material, and dry mixing was performed for 1 hour.

Next, the obtained mixture was put into a platinum crucible and heated at 850°C×1hr to completely melt the flux and then heated at 1100°C×2hr to synthesize Bi _2.5 Na _3.5 Nb ₅ O ₁₈ . In addition, the temperature increase rate was set to 200° C./hr, and the temperature drop was set to furnace cooling. After cooling, the flux was removed from the reactant by hot water washing to obtain a powder of Bi _2.5 Na _3.5 Nb ₅ O ₁₈ . The obtained Bi _2.5 Na _3.5 Nb ₅ O ₁₈ powder is a flaky powder with the {100} plane as the developed plane.

Then, the Bi _2.5 Na _3.5 Nb ₅ O ₁₈ flake powder was added and mixed with Na ₂ CO ₃ powder necessary for the synthesis of NaNbO ₃ , and heat-treated in a platinum crucible at 950°C for 8 hours using NaCl as a flux.

The obtained reactant contains Bi ₂ O ₃ in addition to NaNbO ₃ powder, so after removing the flux from the reactant, put it in NHO ₃ (1N) to dissolve Bi ₂ O ₃ generated as an excess component . Then, the solution was filtered to separate NaNbO ₃ powder, which was washed with ion-exchanged water at 80 °C. The obtained NaNbO ₃ powder is a flaky powder with a pseudo-cubic {100} plane as the developed plane, a particle diameter of 10-30 μm, and an aspect ratio of about 10-20.

A crystal-oriented ceramic having a composition of {Li _0.07 (K _0.43 Na _0.57 ) _0.93 }{Nb _0.84 Ta _0.09 Sb _0.07 }O ₃ was produced as follows.

Weigh Na ₂ CO ₃ powder, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, Sb ₂ O ₅ powder with a purity of 99.99% or more to make it from 1 mol The composition obtained by subtracting 0.05 mol of NaNbO ₃ from the stoichiometric composition of {Li _0.07 (K _0.43 Na _0.57 ) _0.93 }{Nb _0.84 Ta _0.09 Sb _0.07 }O ₃ was carried out for 20 hours with Zr balls in an organic solvent wet mixing. Then, calcined at 750° C. for 5 hours, and then wet pulverized with Zr balls in an organic solvent for 20 hours to obtain calcined powder with an average particle size of about 0.5 μm.

The calcined powder and the above flake-shaped NaNbO ₃ were weighed at a ratio of calcined powder:NaNbO ₃ =0.95 mol:0.05 mol, so that it became {Li _0.07 (K _0.43 Na _0.57 ) _0.93 }{Nb _0.84 The composition of Ta _0.09 Sb _0.07 }O ₃ was wet-mixed with Zr balls for 20 hours in an organic solvent as a medium to obtain pulverized slurry. Then, after adding a binder (polyvinyl butyral) and a plasticizer (butyl phthalate) to the slurry, mixing was performed for another 2 hours.

Then, the mixed slurry was formed into a ribbon having a thickness of about 100 μm using a ribbon forming apparatus. Then, the strip was laminated and crimped and rolled to obtain a sheet-shaped molded body having a thickness of 1.5 mm. Next, the obtained sheet-shaped molded body was degreased in the air under the conditions of heating temperature 600° C., heating time 5 hours, heating rate 50° C./hr, and cooling rate furnace cooling. Further, the degreased sheet-shaped molded body was subjected to CIP treatment at a pressure of 300 MPa, and then sintered at 1110° C. for 5 hours in oxygen gas. In this way, piezoelectric ceramics (crystal-oriented piezoelectric ceramics) were manufactured.

For the obtained piezoelectric ceramics, the sintered density was calculated, and the average orientation degree F (100 ).

Furthermore, by grinding and grinding and processing the obtained piezoelectric ceramics, the piezoelectric ceramics 21 of a disk-shaped sample having a thickness of 0.485 mm and a diameter of 11 mm, as shown in FIG. Au baking electrode paste (gold baking electrodepaste) (manufactured by Sumitomo Metal Mining Co., Ltd., ALP3057) was printed and dried on the upper and lower sides, and baked at 850°C for 10 minutes in a mesh belt furnace. The electrode 20 was formed to a thickness of 0.01 mm. Furthermore, in order to remove protrusions of several micrometers on the outer peripheral portion of the electrode inevitably formed by printing, the obtained disc-shaped sample was processed to a diameter of 8.5 mm by cylindrical grinding. Subsequently, polarization treatment is applied in the vertical direction to obtain the piezoelectric element (single plate) 20 in which the electrodes 210 are formed on the entire surface of the piezoelectric ceramics 21 .

At a temperature of 25° C., the piezoelectric strain constant (d ₃₁ ), electromechanical coupling coefficient (kp), mechanical quality coefficient (Qm), and Permittivity (ε ₃₃ ^t /ε ₀ ) and dielectric loss (tanδ) of dielectric properties.

In addition, similarly, by measuring the temperature characteristic of the permittivity, the first crystal phase transition temperature (Curie temperature) and the second crystal phase transition temperature are obtained. In addition, when the second crystal phase transition temperature is 0°C or lower, since the fluctuation width of the permittivity is very small on the side where the temperature is higher than the second crystal phase transition temperature, when the peak position of the permittivity cannot be confirmed, The temperature at which the permittivity bends is taken as the second crystal phase transition temperature.

Next, a multi-layer piezoelectric element was fabricated using the piezoelectric element obtained above, and a piezoelectric actuator was constructed using the piezoelectric element, and evaluated.

As shown in FIG. 40, first, the piezoelectric element 20 obtained as described above is connected to an internal electrode plate 22 made of SUS having a thickness of 0.02 mm and a diameter of 8.4 mm (23 ) are stacked alternately. At this time, the protrusions of the internal electrode plates 22 ( 23 ) are arranged alternately in different directions in the stacking direction, and the internal electrode plates 22 ( 23 ) are arranged in the same direction for each layer. In this way, a total of 40 piezoelectric ceramics 21 and a total of 41 internal electrode plates 22 (23) are alternately laminated, and further, aluminum oxide plates (insulation plates) with a thickness of 2 mm and a diameter of 8.5 mm are laminated on the upper and lower surfaces of the laminated body, as shown in FIG. 38 As shown, a laminated piezoelectric element 2 is manufactured.

Then, the external electrodes 25 and 26 made of rectangular SUS are welded to the protrusions of the above-mentioned internal electrodes 22 and 23 to be electrically connected in parallel with the piezoelectric element, and then lead terminals 61 and 62 are prepared, and the external electrodes 25 and 26 are connected to the piezoelectric element. The lead terminals 61 and 62 are electrically connected.

In addition, in order to ensure the insulation state between the protrusions of the internal electrode plates 22 and 23 and the internal electrode plates 22 and 23 of the opposite polarity and the Au electrodes of the piezoelectric element of the opposite polarity, the electrodes of the same polarity on the side of the laminated body A comb-shaped resin insulating member (not shown) is inserted between the protrusions of the plate, silicone grease is applied on the top, and the laminate is covered with a holding member 4 composed of an insulating tube to form a laminated piezoelectric element. 2.

Then, in order to improve the adhesion between the Au electrode and the electrode plate of the laminated piezoelectric element 2 , a compressive stress of 150 MPa was applied in the lamination direction at a temperature of 25° C. for 30 seconds (pressure aging). Further, a compressive stress of 30 MPa was applied in the stacking direction at a temperature of 25° C., and in this state, a sine wave with an electric field intensity of 0 to 1500 V/mm was applied at a frequency of 40 Hz for 30 minutes (voltage aging). Then, as shown in FIG. 37, the laminated piezoelectric element 2 is fixed on the jig 8, and the spring constant is 2.9 N/μm with a preset load of 16.4 MPa in the stacking direction of the piezoelectric element 2. Disc spring 85. In this way, the piezoelectric actuator 11 as shown in FIG. 37 is produced.

Next, the obtained piezoelectric actuator is driven by a trapezoidal wave with a constant amplitude at an applied voltage of 485, 728, 970V (electric field strength 0-1000V/mm, 0-1500V/mm, 0-2000V/mm). - Measure the temperature characteristics of displacement and apparent dynamic capacitance within the temperature range of 40°C to 160°C.

The measurement of the displacement adopts the capacitance type displacement sensor, and the observed displacement is measured under the trapezoidal wave driving conditions with the frequency of 0.5Hz and 10Hz, the voltage rise time of 150μs, the voltage drop time of 150μs, and the duty ratio of 50:50.

The apparent dynamic capacitance is measured as follows. A capacitor of 878μF is connected in series to the piezoelectric actuator at a temperature of 25°C. The applied voltage is 485V, 728V, 970V, the frequency is 0.05Hz, and the voltage rise time is 1ms. Under the constant voltage trapezoidal wave drive condition with a voltage drop time of 1 ms, a voltage ON time of 10 s, and a voltage cut-off (OFF) time of 10 s, measure the terminal voltage of the observed capacitor and calculate it by the following formula 11 out.

Apparent dynamic capacitance = {(V (on) - (V (off)) × 878μF) / {applied voltage - (V (on) - V (off))} (11)

(In the formula, apparent dynamic electrostatic capacitance [F], applied voltage [V], V(ON): capacitor terminal voltage [V] 10s after voltage ON, V(OFF): 10s after voltage OFF After the capacitor terminal voltage [V]).

That is, based on the terminal voltage of the capacitor, the accumulated charge of the capacitor (= accumulated charge of the actuator + leaked charge) is obtained, and divided by the applied voltage of the actuator is the apparent dynamic capacitance of the actuator. Here, the voltage applied to the actuator was lowered by connecting the capacitor in series, but the maximum drop was a small value of 0.3V, so it was determined that the applied voltage was the same as the voltage applied to the actuator.

In addition, the fluctuation width in the temperature range of -30°C to 80°C and the fluctuation width in the temperature range of -30°C to 160°C were obtained from the measured values. Here, the fluctuation range is a value based on (maximum value−minimum value)/2.

The relative density of the crystal-oriented ceramics obtained in this example was 95% or more. In addition, the pseudo-cubic {100} planes are oriented parallel to the tape planes, and the average degree of orientation of the pseudo-cubic {100} planes measured by the Lautergelding method is 88.5%. Furthermore, the evaluation results of piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 86.5pm/V, the electromechanical coupling coefficient kp was 48.8%, the mechanical quality coefficient Qm was 18.2, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1042, and the dielectric loss tanδ is 6.4%. In addition, the first crystal phase transition temperature (Curie temperature) obtained from the temperature characteristic of permittivity was 282°C, and the second crystal phase transition temperature was -30°C.

Next, the characteristics of the piezoelectric actuator obtained in this example are described.

The measured apparent dynamic capacitance and the displacement at a frequency of 0.5 Hz, as well as the calculated displacement/apparent dynamic capacitance, displacement/(apparent dynamic capacitance) ^0.5 , and dynamic strain D33 are shown in Table 1, Figure 1, and Figure 2 , and Figure 3.

In addition, the apparent dynamic capacitance, the displacement at a frequency of 0.5Hz, the displacement/apparent dynamic capacitance, the displacement/(apparent dynamic capacitance) ^0.5 , the fluctuation amplitude in the temperature range of -30°C to 80°C, and the fluctuation amplitude at -30°C The fluctuation width in the temperature range of -160 degreeC is shown in Table 12, Table 13, Table 14, and Table 15, respectively.

As can be seen from Table 1, Figure 1, Figure 2, Figure 3, Table 11, Table 12, Table 13, and Table 14, in the piezoelectric actuator of this example, at a temperature of -30°C to 80°C The minimum value of the dynamic strain amount D33 within the range and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is D33=303pm/V when the amplitude of the driving electric field is 1000V/mm and the temperature is -30°C.

· The maximum value of the fluctuation width of the displacement is ±3.8% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±3.2% when the driving electric field amplitude was 1000 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance was ±6.9% when the driving electric field amplitude was 1500 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±5.3% when the driving electric field amplitude is 1500 V/mm.

Next, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is D33=303pm/V when the amplitude of the driving electric field is 1000V/mm and the temperature is -30°C.

· The maximum value of the fluctuation width of the displacement is ±7.7% when the driving electric field amplitude is 2000 V/mm.

·The maximum value of the fluctuation width of the dynamic capacitance is ±28.9% when the driving electric field amplitude is 1000V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±27.8% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width when the displacement/(apparent dynamic capacitance) ^{is 0.5} is ±13.8% when the driving electric field amplitude is 1000 V/mm.

(Example 2)

Except that _the firing temperature of the degreased sheet- _shaped molded body was _set at 1105° _C , the same _procedure as _in Example 1 _was followed to produce _a Composition of crystal-oriented ceramics. With regard to the obtained crystal-oriented ceramics, the sintered body density, average orientation degree, and piezoelectric properties were evaluated under the same conditions as in Example 1. In addition, a laminated actuator of 40 piezoelectric elements was manufactured in the same procedure as in Example 1, and the characteristics of the actuator were evaluated.

The relative density of the crystal-oriented ceramics obtained in this embodiment is above 95%. In addition, the pseudo-cubic {100} planes are oriented parallel to the tape planes, and the average degree of orientation of the pseudo-cubic {100} planes measured by the Lautergelding method is 94.6%. Furthermore, the evaluation results of the piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 88.1pm/V, the electromechanical coupling coefficient kp was 48.9%, the mechanical quality coefficient Qm was 16.6, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1071, and the dielectric loss tanδ is 4.7%. In addition, the first crystal phase transition temperature (Curie temperature) obtained from the temperature characteristic of permittivity was 256°C, and the second crystal phase transition temperature was -35°C.

The characteristics of the piezoelectric actuator of this embodiment are shown in Table 2, FIG. 4, FIG. 5, FIG. 6, Table 11, Table 12, Table 13, and Table 14.

As can be seen from these tables and figures, in the piezoelectric actuator of this example, the minimum value of the dynamic strain D33 in the temperature range of -30°C to 80°C and the fluctuation width of the above characteristics are as follows .

·The minimum value of dynamic strain D33 is D33=355pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 20°C.

· The maximum value of the fluctuation width of the displacement is ±8.0% when the driving electric field amplitude is 1000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance is ±6.3% when the driving electric field amplitude is 1000 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±7.8% when the driving electric field amplitude is 1500 V/mm and 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±6.7% when the driving electric field amplitude is 1000 V/mm.

Next, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of dynamic strain D33 is D33=355pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 20°C.

· The maximum value of the fluctuation amplitude of the displacement is ±13.8% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the dynamic capacitance is ±31.4% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±26.8% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±13.3% when the driving electric field amplitude is 1000 V/mm.

(Example 3)

Except that _the calcining temperature of _the degreased sheet- _shaped molded body _was set at 1105°C, the same _procedure as _in Example 1 _was followed to produce _a Composition of crystal-oriented ceramics. With regard to the obtained crystal-oriented ceramics, the sintered body density, average orientation degree, and piezoelectric properties were evaluated under the same conditions as in Example 1. In addition, a laminated actuator of 40 piezoelectric elements was produced in the same procedure as in Example 1, and the characteristics of the actuator were evaluated.

The relative density of the crystal-oriented ceramics obtained in this embodiment is above 95%. In addition, the pseudo-cubic {100} planes were oriented parallel to the tape planes, and the average degree of orientation of the pseudo-cubic {100} planes measured by the Lautergelding method was 93.9%. In addition, the evaluation results of the piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 95.2pm/V, the electromechanical coupling coefficient kp was 50.4%, the mechanical quality coefficient Qm was 15.9, and the permittivity ( ₃₃ ^t /ε ₀ ) is 1155, and the dielectric loss tanδ is 5.2%. In addition, the first crystal phase transition temperature (Curie temperature) obtained from the temperature characteristic of permittivity was 261°C, and the second crystal phase transition temperature was -12°C.

The characteristics of the piezoelectric actuator of this example are shown in Table 3, FIG. 7, FIG. 8, FIG. 9, Table 11, Table 12, Table 13, and Table 14.

As can be seen from these tables and figures, in the piezoelectric actuator of this example, the minimum value of the dynamic strain D33 in the temperature range of -30°C to 80°C and the fluctuation width of the above characteristics are as follows .

·The minimum value of dynamic strain D33 is D33=347pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 80°C.

· The maximum value of the fluctuation width of the displacement is ±5.6% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance is ±5.2% when the driving electric field amplitude is 1000 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±8.6% when the driving electric field amplitude is 1500 V/mm.

• The maximum value of the fluctuation width when the displacement/(apparent dynamic capacitance) ^{is 0.5} is ±6.9% when the driving electric field amplitude is 1500 V/mm.

Next, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of dynamic strain D33 is D33=347pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 80°C.

· The maximum value of the fluctuation width of the displacement is ±11.5% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the dynamic capacitance is ±34.6% when the driving electric field amplitude is 1000V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±27.1% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width when the displacement/(apparent dynamic capacitance) ^{is 0.5} is ±10.9% when the driving electric field amplitude is 1000 V/mm.

(Example 4)

In this example, a crystal-oriented piezoelectric ceramic having the same composition as that of Example 1 was produced by a different procedure from that of Example 1, and a piezoelectric actuator was produced using this crystal-oriented piezoelectric ceramic.

That is, first, the NaNbO ₃ flake powder produced in Example 1, and the non-flaky NaNbO ₃ powder, KNbO ₃ powder, KTaO ₃ powder, LiSbO ₃ powder, and NaSbO ₃ powder were weighed to make {Li _0.07 (K _0.43 Na _0.57 ) _0.93 }{Nb _0.84 Ta _0.09 Sb _0.07 }O ₃ was wet-mixed for 20 hours using an organic solvent as a solvent.

After adding a binder (polyvinyl butyral) and a plasticizer (dibutyl phthalate) to the slurry, mixing was performed for another 2 hours.

Furthermore, the compounding amount of NaNbO ₃ flakes was set such that 5 wt % of the A-site elements of the first KNN-based solid solution (ABO ₃ ) synthesized from the starting material was supplied from the NaNbO ₃ flakes. In addition, the non-flaky NaNbO ₃ powder, KNbO ₃ powder, KTaO ₃ powder, LiSbO ₃ powder, and NaSbO ₃ powder are obtained by the solid-phase method, that is, K ₂ CO ₃ powder with a purity of 99.9%, Na ₂ A mixture of CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, and/or Sb ₂ O ₅ powder was heated at 750° C. for 5 hours, and then the reactant was pulverized by a ball mill.

Next, the mixed slurry was formed into a ribbon having a thickness of about 100 μm using a ribbon forming apparatus. Then, the strip was laminated, crimped, and rolled to obtain a sheet-shaped molded body with a thickness of 1.5 mm. Next, the obtained sheet-shaped molded body was degreased in air under the conditions of heating temperature of 600°C, heating time of 5 hours, heating rate of 50°C/hr, and cooling rate of furnace cooling. Furthermore, after degreasing the sheet-shaped molded body with a pressure of 300 MPa, after CIP treatment, the sintering temperature in oxygen is 1130 ° C, the heating time is 5 hours, and the heating and cooling rate is 200 ° C / hr. Hot press sintering was performed applying a pressure of 35 kg/cm ² (3.42 MPa) during the heating time. In this way, piezoelectric ceramics (crystal-oriented piezoelectric ceramics) were fabricated.

The relative density of the crystal-oriented ceramics obtained in this embodiment is above 95%. In addition, the pseudo-cubic {100} planes are oriented parallel to the tape planes, and the average degree of orientation of the pseudo-cubic {100} planes measured by the Lautergelding method is 96%. Furthermore, the evaluation results of the piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 96.5pm/V, the electromechanical coupling coefficient kp was 51.9%, the mechanical quality coefficient Qm was 15.2, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1079, and the dielectric loss tanδ is 4.7%. In addition, the first crystal phase transition temperature (Curie temperature) obtained from the temperature characteristic of permittivity was 279°C, and the second crystal phase transition temperature was -28°C.

The characteristics of the piezoelectric actuator of this example are shown in Table 4, FIG. 10, FIG. 11, FIG. 12, Table 11, Table 12, Table 13, and Table 14.

As can be seen from these tables and figures, in the piezoelectric actuator of this example, the minimum value of the dynamic strain D33 in the temperature range of -30°C to 80°C and the fluctuation width of the above characteristics are as follows .

·The minimum value of dynamic strain D33 is D33=427pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 50°C.

· The maximum value of the fluctuation width of the displacement is ±7.2% when the driving electric field amplitude is 1000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±6.1% when the driving electric field amplitude was 2000 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±8.0% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±6.7% when the driving electric field amplitude is 1000 V/mm.

Next, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of dynamic strain D33 is D33=427pm/V when the driving electric field amplitude is 1000V/mm and the temperature is 50°C.

· The maximum value of the fluctuation width of the displacement is ±9.4% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the dynamic capacitance is ±28.4% when the driving electric field amplitude is 2000V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±32.4% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±19.5% when the driving electric field amplitude is 1000 V/mm.

(Example 5)

In this example _, a piezoelectric ceramic having a composition in which 0.0005 mol of Mn was added to 1 mol of the composition of Example 3 {Li _0.065 (K _0.45 Na _0.55 ) _0.935 }{Nb _0.83 Ta _0.09 Sb _0.08 }O 3 ( Crystal-oriented piezoelectric ceramics), which are used to make piezoelectric actuators.

First, weigh Na ₂ CO ₃ powder, K ₂ CO ₃ powder, Li ₂ CO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, Sb ₂ O ₅ powder, and MnO ₂ powder with a purity of 99.99% or more , so that it becomes a composition obtained by subtracting 0.05 mol of NaNbO ₃ from the composition of {Li _0.07 (K _0.43 Na _0.57 ) _0.93 }{Nb _0.84 Ta _0.09 Sb _0.07 }O ₃ 1mol+Mn 0.0005mol, using an organic solvent as Medium, 20 hours of wet mixing with Zr balls. Then, calcined at 750° C. for 5 hours, and then wet pulverized with Zr balls in an organic solvent for 20 hours to obtain calcined powder with an average particle size of about 0.5 μm.

In the subsequent steps, except _that the firing _temperature of the degreased sheet-shaped molded body was set to 1105°C, the _same procedure as in Example 1 _was followed to _produce Crystal-oriented ceramics with a composition of _0.09 Sb _0.08 }O ₃ 1mol+Mn 0.0005mol.

For the obtained crystal-oriented ceramics, the sintered body density, average orientation degree, and voltage characteristics were evaluated under the same conditions as in Example 1. In addition, a laminated actuator of 40 piezoelectric elements was produced in the same procedure as in Example 1, and the characteristics of the actuator were evaluated. Furthermore, the electrostatic capacitance of the actuator was evaluated under the conditions that the amplitude of the electric field intensity was 2 V/mm (±1 V), a sine wave, and a frequency of 1 kHz.

The relative density of the crystal-oriented ceramics obtained in this embodiment is above 95%. Furthermore, the pseudo-cubic {100} planes were oriented parallel to the tape planes, and the average degree of orientation of the pseudo-cubic {100} planes measured by the Lautergelding method was 89.6%. In addition, the evaluation results of the piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 99.1pm/V, the electromechanical coupling coefficient kp was 52.0%, the mechanical quality coefficient Qm was 20.3, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1159, and the dielectric loss tanδ is 2.7%. It is known from this that the addition of Mn has the effect of increasing Qm and reducing tanδ.

In addition, the first crystal phase transition temperature (Curie temperature) obtained from the temperature characteristic of permittivity was 263°C, and the second crystal phase transition temperature was -15°C.

The characteristics of the piezoelectric actuator of this embodiment are shown in Table 5, FIG. 13, FIG. 14, FIG. 15, Table 11, Table 12, Table 13, and Table 14.

As can be seen from these tables and figures, in the piezoelectric actuator of this example, the minimum value of the dynamic strain D33 in the temperature range of -30°C to 80°C and the fluctuation width of the above characteristics are as follows .

·The minimum value of the dynamic strain D33 is D33=355pm/V when the driving electric field amplitude is 1000V/mm, and the temperature is 50°C and 80°C.

· The maximum value of the fluctuation width of the displacement is ±10.4% when the driving electric field amplitude is 1000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±4.9% when the driving electric field amplitude was 1000 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±10.7% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±7.2% when the driving electric field amplitude is 1000 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is D33=355pm/V when the driving electric field amplitude is 1000V/mm, and the temperature is 50°C and 80°C.

· The maximum value of the fluctuation width of the displacement is ±11.8% when the driving electric field amplitude is 1000 V/mm.

·The maximum value of the fluctuation width of the dynamic capacitance is ±26.9% when the driving electric field amplitude is 1000V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±21.3% when the driving electric field amplitude is 1000 V/mm.

• The maximum value of the fluctuation width of displacement/(apparent dynamic capacitance) ^0.5 is ±12.4% when the driving electric field amplitude is 1000 V/mm.

From this result, it is known that the addition of Mn has the effect of reducing the fluctuation width of the apparent dynamic capacitance in the temperature range of -30°C to 160°C.

In addition, the electrostatic capacitance of the piezoelectric actuator of this example will be described.

The electrostatic capacitance of the piezoelectric actuator of this example is a value smaller than the apparent dynamic capacitance in the range of -30°C to 160°C. Furthermore, the fluctuation width in the range of -30°C to 80°C was ±4.8%, which was almost the same as the fluctuation width of the apparent dynamic capacitance when the electric field strength was 1000 V/mm. On the other hand, the fluctuation width in the range of −30° C. to 160° C. was ±5.2%, which was a value much smaller than the fluctuation width of the apparent dynamic capacitance. It is considered that the difference between the dynamic capacitance and the electrostatic capacitance is determined by the difference in electric field intensity.

Therefore, it can be considered that the reason for the difference in fluctuation amplitude is: in the high temperature range above 80°C, when the electric field strength is above 1000V/mm, the apparent dynamic capacitance increases due to the increase of leakage current, but on the other hand , when the electric field strength is 2V/mm, there is almost no leakage current, and the electrostatic capacitance does not increase.

From the above, in the piezoelectric actuator of this example, by making the driving electric field strength less than 1000V/mm, the fluctuation width of the apparent dynamic capacitance can be reduced in a wide temperature range of -30°C to 160°C. It can be considered that the possible level can reach the same level as the temperature characteristic of the dynamic capacitance of the single board.

(comparative example 1)

This comparative example is an example of a laminated actuator using a square PZT material with intermediate characteristics (semi-hard) between soft and hard systems. This laminated actuator is suitable for laminated actuators for automotive fuel injection valves. element. Here, the soft type refers to a material with a Qm of 100 or less, and the so-called hard type refers to a material with a Qm of 1000 or more. Laminated actuators for fuel injection valves are used in constant voltage control, constant energy control or constant charge control, and the valve is driven by trapezoidal waves to open and close, thereby controlling the spray of fuel. The characteristics of the actuator require high displacement performance and small temperature characteristics of displacement in each control method.

Weigh PbO powder, ZrO ₂ powder, TiO ₂ powder, SrCO ₃ powder, Y ₂ O ₃ powder, Nb ₂ O ₅ powder, Mn ₂ O ₃ powder to make (Pb _0.92 Sr _0.09 ){(Zr _0.543 Ti _0.457 ) _0.985 (Y _0.5 Nb _0.5 ) _0.01 Mn _0.005 }O ₃ composition, using water as medium, wet mixing with Zr balls. Then, it was calcined at 790° C. for 7 hours, and wet pulverized with Zr balls using an organic solvent as a medium to obtain a slurry of calcined powder with an average particle size of about 0.7 μm.

After adding a binder (polyvinyl butyral) and a plasticizer (butyl benzyl phthalate) to this slurry, it mixed with Zr balls for 20 hours.

Next, the mixed slurry is formed into a strip with a thickness of about 100 μm by a strip forming device, and then the strip is laminated and thermocompressed to obtain a sheet-shaped molded body with a thickness of 1.2 mm. The obtained sheet-shaped molded body was degreased. Furthermore, the degreased sheet-shaped molded body was placed on a MgO plate in an alumina sinter, and sintered at 1170° C. for 2 hours in the air. In subsequent steps, firing was performed in the same manner as in Example 1 except that Ag paste was used as the electrode material.

The relative density of the piezoelectric ceramic of this comparative example was 95% or more. In addition, the evaluation results of piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 158.0pm/V, the electromechanical coupling coefficient kp was 60.2%, the mechanical quality coefficient Qm was 540, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1701, and the dielectric loss tanδ is 0.2%.

The actuator characteristics of this comparative example are shown in Table 6, FIG. 16, FIG. 17, FIG. 18, Table 15, Table 16, Table 17, and Table 18.

As can be seen from these tables and figures, the minimum value of the dynamic strain amount D33 and the fluctuation width of the above-mentioned characteristics of the piezoelectric actuator of this comparative example in the temperature range of -30°C to 70°C are as follows.

· The minimum value of the dynamic strain D33 is 553 pm/V when the driving electric field amplitude is 2000 V/mm and 1500 V/mm, and the temperature is -30°C.

· The maximum value of the fluctuation width of the displacement is ±5.6% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±14.5% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance is ±10.5% when the driving electric field amplitude is 1500 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

· The minimum value of the dynamic strain D33 is 553 pm/V when the driving electric field amplitude is 2000 V/mm and 1500 V/mm, and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±11.1% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±33.5% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance was ±23.7% when the driving electric field amplitude was 1500 V/mm.

(comparative example 2)

This comparative example 2 is an example of a laminated actuator using a soft rhombohedral PZT material, and this laminated actuator is suitable as a laminated actuator for determining the position of a semiconductor manufacturing device where the ambient temperature changes little. Multilayer actuators for position determination are used in places where the ambient temperature changes little, so high displacement performance is required, but excellent temperature characteristics are not required.

Weigh PbO powder, ZrO ₂ powder, TiO ₂ powder, SrCO ₃ powder, Y ₂ O ₃ powder, Nb ₂ O ₅ powder to make (Pb _0.895 Sr _0.115 ) {(Zr _0.57 Ti _0.43 ) _0.978 (Y _0.5 Nb The composition of _0.5 ) _0.01 Nb _0.012 }O ₃ was wet mixed with Zr balls for 20 hours in water as medium. Then, it was calcined at 875° C. for 5 hours, and then wet pulverized with Zr balls using water as a medium. A binder (polyvinyl alcohol) was added to the slurry to make it 1% by weight of the calcined powder, followed by drying and granulation with a spray dryer.

Next, a molded body having a diameter of φ15 mm and a thickness of 2 mm was obtained by dry press molding using a mold. Then, the obtained disc-shaped compact was degreased in the air. Furthermore, the degreased sheet-shaped compact was subjected to CIP treatment at a pressure of 200 MPa, placed on an MgO plate in an alumina sinter, and sintered at 1260° C. for 2 hours in the air. Subsequent steps are the same as in Comparative Example 1.

The relative density of the piezoelectric ceramic of this comparative example was 95% or more. In addition, the evaluation results of piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 212.7pm/V, the electromechanical coupling coefficient kp was 67.3%, the mechanical quality coefficient Qm was 47.5, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1943, and the dielectric loss tanδ is 2.1%.

The actuator characteristics of this comparative example are shown in Table 7, FIG. 19, FIG. 20, FIG. 21, Table 15, Table 16, Table 17, and Table 18.

As can be seen from these tables and figures, the minimum value of the dynamic strain D33 and the fluctuation width of the above-mentioned characteristics of the piezoelectric actuator of this example in the temperature range of -30°C to 70°C are as follows.

·The minimum value of the dynamic strain D33 is 482pm/V when the driving electric field amplitude is 2000V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±23.7% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±37.9% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance is ±15.5% when the driving electric field amplitude is 1500 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is 482pm/V when the driving electric field amplitude is 2000V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±38.5% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±63.5% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance was ±33.1% when the driving electric field amplitude was 2000 V/mm and 1500 V/mm.

(comparative example 3)

This comparative example 3 is an example of a laminated actuator using a soft tetragonal PZT material, and this laminated actuator is suitable for a knock sensor for an automobile. The knock sensor uses the piezoelectric effect of piezoelectric ceramics to convert the knock of the gasoline engine into a voltage for detection, and does not function as an actuator.

Weigh PbO powder, ZrO ₂ powder, TiO ₂ powder, SrTiO ₃ powder, Sb ₂ O ₃ powder to make it a composition of (Pb _0.95 Sr _0.05 ){(Zr _0.53 Ti _0.47 ) _0.978 Sb _0.022 }O ₃ As a medium, Zr balls were used for 20 hours of wet mixing. Then, pre-calcination was performed at 825° C. for 5 hours, and then wet pulverization was performed with Zr balls using water as a medium. In subsequent steps, it was the same as that of Comparative Example 2 except that the sintering temperature was set to 1230°C.

The relative density of the piezoelectric ceramic of this comparative example was 95% or more. In addition, the evaluation results of piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 203.4pm/V, the electromechanical coupling coefficient kp was 62.0%, the mechanical quality coefficient Qm was 55.8, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 2308, and the dielectric loss tanδ is 1.4%.

The actuator characteristics of this comparative example are shown in Table 8, Figure 22, Figure 23, Figure 24, Table 15, Table 16, Table 17, and Table 18.

As can be seen from these tables and figures, the minimum value of the dynamic strain amount D33 and the fluctuation width of the above-mentioned characteristics of the piezoelectric actuator of this comparative example in the temperature range of -30°C to 70°C are as follows.

·The minimum value of the dynamic strain D33 is 663pm/V when the driving electric field amplitude is 1500V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±10.4% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±17.9% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance is ±10.2% when the driving electric field amplitude is 1500 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is 663pm/V when the driving electric field amplitude is 1500V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±14.8% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±32.3% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance was ±18.4% when the driving electric field amplitude was 1500 V/mm.

(comparative example 4)

This Comparative Example 4 is an example of a laminated actuator using a semi-rigid tetragonal PZT material, and this laminated actuator is suitable for a high-power ultrasonic motor. The ultrasonic motor drives the piezoelectric ceramic ring pasted on the stator to resonate at several 10 kHz, and rotates the rotor crimped on the stator. For the characteristics of the actuator, high displacement performance and excellent temperature characteristics of displacement are required.

Weigh PbO powder, ZrO ₂ powder, TiO ₂ powder, SrCO ₃ powder, Sb ₂ O ₃ powder, MnCO ₃ powder to make (Pb _0.965 Sr _0.05 ){(Zr _0.5 Ti _0.5 ) _0.96 Sb _0.03 Mn _0.01 }O The composition of ₃ uses water as the medium and performs wet mixing with Zr balls. Then, it was calcined at 875° C. for 5 hours, and then wet pulverized with Zr balls using water as a medium. In subsequent steps, it was the same as that of Comparative Example 2 except that the sintering temperature was set to 1230°C.

The relative density of the piezoelectric ceramic of this comparative example was 95% or more. As a result of the evaluation of the piezoelectric characteristics at a temperature of 25°C, the piezoelectric d ₃₁ constant was 136.9pm/V, the electromechanical coupling coefficient kp was 57.9%, the mechanical quality coefficient Qm was 850, and the permittivity (ε ₃₃ ^t /ε ₀ ) It is 1545, and the dielectric loss tanδ is 0.2%.

The actuator characteristics of this comparative example are shown in Table 9, FIG. 25 , FIG. 26 , FIG. 27 , Table 15, Table 16, Table 17, and Table 18.

As can be seen from these tables and figures, the minimum value of the dynamic strain amount D33 and the fluctuation width of the above-mentioned characteristics of the piezoelectric actuator of this comparative example in the temperature range of -30°C to 70°C are as follows.

·The minimum value of the dynamic strain D33 is 409pm/V when the driving electric field amplitude is 1500V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±6.0% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±15.8% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance is ±11.5% when the driving electric field amplitude is 1500 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is 409pm/V when the driving electric field amplitude is 1500V/mm and the temperature is -30°C.

· The maximum value of the fluctuation amplitude of the displacement is ±15.2% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±36.7% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance was ±22.7% when the driving electric field amplitude was 1500 V/mm.

(comparative example 5)

Comparative Example 5 is an example of a laminated actuator using a hard-based tetragonal PZT material, and this laminated actuator is suitable for a high-sensitivity angular velocity sensor. The angular velocity sensor has both an actuator function to resonate and drive a piezoelectric ceramic tuning fork at a frequency of several kHz, and a sensor function to detect angular velocity. For the characteristics of the actuator, the displacement performance can be low, but the temperature characteristic of the displacement is required to be small.

Weigh PbO powder, ZrO ₂ powder, TiO ₂ powder, ZnO powder, MnCO ₃ powder, Nb ₂ O ₅ powder to make Pb{(Zr _0.5 Ti _0.5 ) _0.98 (Zn _0.33 Nb _0.67 ) _0.01 Mn _0.01 }O ₃ The composition, using water as the medium, wet mixing with Zr balls. Then, it was calcined at 800° C. for 5 hours, and then wet pulverized with Zr balls using water as a medium. In subsequent steps, it was the same as in Comparative Example 2 except that the sintering temperature was set to 1200°C.

The relative density of the piezoelectric ceramic of this comparative example was 95% or more. In addition, the evaluation results of piezoelectric characteristics at a temperature of 25°C showed that the piezoelectric d ₃₁ constant was 103.6pm/V, the electromechanical coupling coefficient kp was 54.1%, the mechanical quality coefficient Qm was 1230, and the permittivity (ε ₃₃ ^t /ε ₀ ) is 1061, and the dielectric loss tanδ is 0.2%.

The actuator characteristics of this comparative example are shown in Table 10, FIG. 28, FIG. 29, FIG. 30, Table 15, Table 16, Table 17, and Table 18.

As can be seen from these tables and figures, the minimum value of the dynamic strain amount D33 and the fluctuation width of the above-mentioned characteristics of the piezoelectric actuator of this comparative example in the temperature range of -30°C to 70°C are as follows.

·The minimum value of the dynamic strain D33 is 295pm/V when the driving electric field amplitude is 1500V/mm and the temperature is 20°C. The minimum value of the dynamic strain D33 is smaller than 303 pm/V in Example 1.

· The maximum value of the fluctuation amplitude of the displacement is ±3.2% when the driving electric field amplitude is 2000 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±14.3% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation amplitude of the displacement/apparent dynamic capacitance was ±13.9% when the driving electric field amplitude was 1500 V/mm.

In addition, the minimum value of the dynamic strain amount D33 in the temperature range of -30°C to 160°C and the fluctuation width of the above-mentioned characteristics are as follows.

·The minimum value of the dynamic strain D33 is 295pm/V when the driving electric field amplitude is 1500V/mm and the temperature is 20°C.

· The maximum value of the fluctuation amplitude of the displacement is ±11.1% when the driving electric field amplitude is 1500 V/mm.

· The maximum value of the fluctuation width of the apparent dynamic capacitance was ±32.4% when the driving electric field amplitude was 1500 V/mm.

· The maximum value of the fluctuation width of the displacement/apparent dynamic capacitance is ±24.5% when the driving electric field amplitude is 1500 V/mm.

(Embodiment 6) Separation of Leakage Current and Capacitance

In this example, in order to examine whether the increase in apparent dynamic capacitance at 80°C or higher as shown in Examples 1 to 5 is caused by an increase in leakage current as in Example 5, Examples 1 and 4 were used. , and the piezoelectric ceramic (single plate) produced in Comparative Example 1, the temperature characteristics of the dynamic capacitance were evaluated.

Here, the dynamic capacitance is measured as follows. When driving with a triangular wave with a frequency of 1 Hz and applying a high voltage with an electric field strength of 2000 V/mm (0 to 970 V), the following equation A9 is used to calculate the polarization-voltage The hysteresis loop measures the amount of polarization, and based on this, the amount of injected charge when driving under high electric field is calculated and used as a dynamic capacitance.

Dynamic capacitance C＝Q/V A9

In the formula, V: Applied voltage (=970V), Q: Maximum charge [C].

When a voltage is repeatedly applied to the single boards produced in Examples 1 and 4 in a temperature range above 80° C., the phenomenon of zero-point shift of the polarization amount occurs due to leakage current. Therefore, in order to evaluate the hysteresis loop, the voltage-polarization characteristic observed by repeatedly applying the voltage 10 times was corrected so that when the voltage = 0, the polarization = 0, and the linear resistance was connected in parallel The model obtains the hysteresis loop by removing the leakage current. The dynamic capacitance obtained from this hysteresis loop is different from the apparent dynamic capacitance, and is obtained by dividing the applied voltage by the charged charge from the dielectric component, polarization reversal component, and polarization rotation component after removing the leakage current. of. Draw the hysteresis loop repeatedly 10 times, and take the average value of the maximum charge as the polarization.

On the other hand, even when voltage was repeatedly applied to the single plate produced in Comparative Example 1, there was no zero-point shift of the polarization amount. In the evaluation of the hysteresis loop, the average value of the maximum charge amount observed after repeating the voltage application 10 times in the same manner as above was used as the polarization amount.

In addition, the dynamic capacitance of the single board obtained in this way is multiplied by the number of elements of the actuator 40, and the results of comparison with the apparent dynamic capacitance of the actuators produced in Example 1, Example 4, and Comparative Example 1 are shown respectively. In Figure 31, Figure 32, and Figure 33.

As can be seen from Fig. 31, Fig. 32, and Fig. 33, the values of (the apparent dynamic capacitance of the actuator) and (the dynamic capacitance of the single board × 40) of Comparative Example 1 are roughly the same, but the values of the comparison example 1 and In Example 4, the values of (the apparent dynamic capacitance of the actuator) and (the dynamic capacitance of the single board×40) are very different. (Apparent dynamic capacitance of the actuator) increases in the high-temperature region above 80°C, but the value of (dynamic capacitance of the single board × 40) is approximately constant. The fluctuation width (dynamic capacitance of the single board×40) in the temperature range of -30°C to 160°C was ±7.6% in Example 1 and ±2.2% in Example 4.

From the above, if the piezoelectric actuator of the present invention reduces the leakage current at a high temperature of about 80°C or higher, or conversely increases the leakage current at a temperature below 80°C, in the wide temperature range of -30°C to 160°C, even It is driven by a high electric field with a driving electric field strength of 2000V/mm, and the fluctuation amplitude of the apparent dynamic capacitance can also be reduced. It can be considered that the possible level can reach the same level as the temperature characteristic of the dynamic capacitance of the single board.

(Embodiment 7) Regulation of the lower limit of the dynamic strain

As shown in Example 5, by making the driving electric field strength less than 1000 V/mm, the fluctuation width of the apparent dynamic capacitance can be reduced in a wide temperature range of -30°C to 160°C. However, if the driving electric field strength is reduced, the amount of dynamic strain is also reduced. In this example, the amount of dynamic strain of the actuator of the present invention was obtained when the intensity of the driving electric field was lowered.

The relationship between the driving electric field intensity and the dynamic strain at 20°C of the actuators produced in Examples 1 to 5 is shown in FIG. 34 . It can be seen that the dynamic strain is 250 pm/V or more at 100 V/mm, which is the lower limit of the driving electric field strength required for the actuator.

(Embodiment 8) Regulation of the temperature characteristics of the dynamic strain amount in a low electric field

In this example, the fluctuation amplitude of the displacement is obtained when the dynamic strain amount is small at a low driving electric field strength of less than 1000 V/mm.

Therefore, it is necessary to reduce the applied voltage to the piezoelectric actuator for measurement. For the piezoelectric actuator manufactured in this embodiment, when the electric field strength is less than 500V/mm, the displacement is small and the measurement accuracy may deteriorate. In addition, the evaluation of its temperature characteristics is more difficult.

Therefore, if the piezoelectric transverse strain constant d ₃₁ of the veneer is measured, although it is difficult to estimate the absolute value of the displacement, it is possible to estimate the temperature characteristic of the displacement. Therefore, in this embodiment, the resonance-anti-resonance method is used to The measurement of the piezoelectric transverse strain constant d ₃₁ of the single plate was carried out.

The measured value of the temperature characteristic of the piezoelectric d ₃₁ constant of the single plate produced in Example 5 and the dynamic strain amount obtained in Example 5 at a driving electric field strength of 1000 to 2000 V/mm were normalized to the value at 20°C, respectively. The results of the comparison are shown in FIG. 35 . The fluctuation width of the piezoelectric _d31 constant of the single plate in the temperature range of -30°C to 80°C was ±7.8% in Example 5. In addition, the fluctuation width of the piezoelectric _d31 constant of the single plate in the temperature range of -30°C to 160°C was ±7.8% in Example 5. This value is the same as or a smaller value than the fluctuation width of the dynamic strain amount at a driving electric field strength of 1000 to 2000 V/mm.

From the above, it is known that even if the driving electric field intensity is lower than 1000V/mm, the actuator of the present invention can reduce the fluctuation amplitude of the displacement in a wide temperature range of -30°C to 160°C.

Table 11

Table 12

Table 13

Table 14

Table 15

Table 16

Table 17

Table 18

Claims (21)

1. piezoelectric-actuator, it has the piezoelectric element that forms 1 pair of electrode on the surface of piezoelectric ceramic and constitute as drive source, it is characterized in that: to described piezoelectric-actuator applied voltage, it with electric field strength the occasion that the electric field driven condition with uniform amplitude more than the 100V/mm makes its driving, described piezoelectric-actuator satisfies at least one important document in the following important document (a)～(c)

(a) following formula, (1) the fluctuation width of cloth WC[% that varies with temperature generation of Biao Shi apparent dynamic capacity C] be in ± 11% in-30 ℃～80 ℃ specific range of temperatures, wherein, C is the apparent dynamic capacity of described piezoelectric-actuator, when described piezoelectric-actuator is connected with capacitors in series, and during to described piezoelectric-actuator and described capacitor applied voltage, C can be by calculating divided by the voltage V that is applied on the described piezoelectric-actuator with the quantity of electric charge Q that puts aside in the described capacitor

W _C(％)＝[{2×C _max/(C _max+C _min)}—1]×100 (1)

Wherein, C _MaxBe illustrated in the maximum of-30 ℃～80 ℃ apparent dynamic capacity, C _MinBe illustrated in the minimum value of-30 ℃～80 ℃ apparent dynamic capacity;

(b) the fluctuation width of cloth W that varies with temperature generation of the displacement L of following formula (2) expression _L[%] is in ± 14% in-30 ℃～80 ℃ specific range of temperatures, and wherein, L is the displacement of described piezoelectric-actuator,

W _L[％]＝[{2×L _max/(L _max+L _min)}—1]×100 (2)

Wherein, L _MaxBe illustrated in the maximum of-30 ℃～80 ℃ displacement, L _MinBe illustrated in the minimum value of-30 ℃～80 ℃ displacement;

(c) the fluctuation width of cloth W that varies with temperature generation of the L/C of following formula (3) expression _L/CIn-30 ℃～80 ℃ specific range of temperatures, be in ± 12% (%), wherein, C is the apparent dynamic capacity of described piezoelectric-actuator, L is the displacement of described piezoelectric-actuator, when described piezoelectric-actuator is connected with capacitors in series, and during to described piezoelectric-actuator and described capacitor applied voltage, described C can be by calculating divided by the voltage V that is applied on the described piezoelectric-actuator with the quantity of electric charge Q that puts aside in the described capacitor

W _L/C[％]＝[{2×(L/C) _max/((L/C) _max+(L/C) _min)}—1]×100 (3)

Wherein, (L/C) _MaxBe illustrated in the maximum of-30 ℃～80 ℃ L/C, (L/C) _MinBe illustrated in the minimum value of-30 ℃～80 ℃ L/C,

The unit of described apparent dynamic capacity C is F, and the unit of described quantity of electric charge Q is C, and the unit of described voltage V is V, and the unit of the displacement L of described piezoelectric-actuator is μ m;

Described piezoelectric ceramic is by with general formula: { Li _x(K _1-yNa _y) _1-x{ Nb _1-z-wTa _zSb _wO ₃The isotropism perovskite-type compounds of expression constitutes as the polycrystal of principal phase, while is made of the crystal orientation piezoelectric ceramic that the particular crystal plane that constitutes described multicrystal each crystal grain is in state of orientation, in the following formula, 0＜x≤0.2,0≤y≤1,0＜z≤0.4,0＜w≤0.2, x+z+w〉0.

2. piezoelectric-actuator according to claim 1 is characterized in that: satisfy described important document (a) and described important document (b) the two.

3. piezoelectric-actuator according to claim 1 is characterized in that: the whole important documents that satisfy described important document (a)～(c).

4. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (d),

(d) L/C of following formula (4) expression ^0.5The fluctuation width of cloth W that varies with temperature generation _L/C ^0.5, in-30 ℃～80 ℃ specific range of temperatures, be in ± 12%, wherein, L/C ^0.5Be the displacement L of described piezoelectric-actuator and the ratio of the square root of described apparent dynamic capacity C,

W _L/C ^0.5(％)＝[{2×(L/C ^0.5) _max/((L/C ^0.5) _max+(L/C ^0.5) _min)}—1]×100

(4)

In the formula, (L/C ^0.5) _MaxBe illustrated in-30 ℃～80 ℃ L/C ^0.5Maximum, (L/C ^0.5) _MinBe illustrated in-30 ℃～80 ℃ L/C ^0.5Minimum value.

5. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (e),

(e) in-30 ℃～80 ℃ specific range of temperatures, be more than the 250pm/V by the dynamic strain amount of calculating divided by electric field strength in the strain of extra electric field direction with described piezoelectric-actuator.

6. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (f),

(f) described fluctuation width of cloth W _C[%] is in ± 35% in-30 ℃～160 ℃ specific range of temperatures.

7. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (g),

(g) described fluctuation width of cloth W _L[%] is in ± 14% in-30 ℃～160 ℃ specific range of temperatures.

8. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (h),

(h) described fluctuation width of cloth W _L/C[%] is in ± 35% in-30 ℃～160 ℃ specific range of temperatures.

9. piezoelectric-actuator according to claim 1 is characterized in that: also satisfy following important document (i),

(i) described fluctuation width of cloth W _L/C ^0.5[%] is in ± 20% in-30 ℃～160 ℃ specific range of temperatures.

10. piezoelectric-actuator, it has the piezoelectric element that forms 1 pair of electrode on the surface of piezoelectric ceramic and constitute as drive source, it is characterized in that: to described piezoelectric-actuator applied voltage, it with electric field strength the occasion that the electric field driven condition with uniform amplitude more than the 100V/mm makes its driving, described piezoelectric-actuator satisfies at least one important document in following important document (j)～(1)

(j) the fluctuation width of cloth W that varies with temperature generation of the apparent dynamic capacity C of following formula (5) expression _C[%] is in ± 30% in-30 ℃～160 ℃ specific range of temperatures, wherein, C is the apparent dynamic capacity of described piezoelectric-actuator, when described piezoelectric-actuator is connected with capacitors in series, and during to described piezoelectric-actuator and described capacitor applied voltage, C can be by calculating divided by the voltage V that is applied on the described piezoelectric-actuator with the quantity of electric charge Q that puts aside in the described capacitor

W _C(％)＝[{2×C _max/(C _max+C _min)}—1]×100 (5)

Wherein, C _MaxBe illustrated in the maximum of-30 ℃～160 ℃ apparent dynamic capacity, C _MinBe illustrated in the minimum value of-30 ℃～160 ℃ apparent dynamic capacity;

(k) the fluctuation width of cloth W that varies with temperature generation of the displacement L of following formula (6) expression _L[%] is in ± 14% in-30 ℃～160 ℃ specific range of temperatures, and wherein, L is the displacement of described piezoelectric-actuator,

W _L[％]＝[{2×L _max/(L _max+L _min)}—1]×100 (6)

Wherein, L _MaxBe illustrated in the maximum of-30 ℃～160 ℃ displacement, Lmin is illustrated in the minimum value of-30 ℃～160 ℃ displacement;

(l) the fluctuation width of cloth W that varies with temperature generation of the L/C of following formula (7) expression _L/C(%), in-30 ℃～160 ℃ specific range of temperatures, be in ± 35%, wherein, C is the apparent dynamic capacity of described piezoelectric-actuator, L is the displacement of described piezoelectric-actuator, when described piezoelectric-actuator is connected with capacitors in series, and during to described piezoelectric-actuator and described capacitor applied voltage, described C can by with the quantity of electric charge Q that puts aside in the described capacitor divided by the voltage V[V that is applied on the described piezoelectric-actuator] calculate

W _L/C[％]＝[{2×(L/C) _max/((L/C) _max+(L/C) _min)}—1]×100 (7)

Wherein, (L/C) _MaxBe illustrated in the maximum of-30 ℃～160 ℃ L/C, (L/C) _MinBe illustrated in the minimum value of-30 ℃～160 ℃ L/C,

The unit of described apparent dynamic capacity C is F, and the unit of described quantity of electric charge Q is C, and the unit of described voltage V is V, and the unit of the displacement L of described piezoelectric-actuator is μ m;

Described piezoelectric ceramic is by with general formula: { Li _x(K _1-yNa _y) _1-x{ Nb _1-z-wTa _zSb _wO ₃The isotropism perovskite-type compounds of expression constitutes as the polycrystal of principal phase, while is made of the crystal orientation piezoelectric ceramic that the particular crystal plane that constitutes described multicrystal each crystal grain is in state of orientation, in the following formula, 0＜x≤0.2,0≤y≤1,0＜z≤0.4,0＜w≤0.2, x+z+w〉0.

11. piezoelectric-actuator according to claim 10 is characterized in that: satisfy described important document (j) and described important document (k) these two.

12. piezoelectric-actuator according to claim 10 is characterized in that: the whole important documents that satisfy described important document (j)～(1).

13. piezoelectric-actuator according to claim 10 is characterized in that: also satisfy following important document (m),

(m) L/C of following formula (8) expression ^0.5The fluctuation width of cloth W that varies with temperature generation _L/C ^0.5[%] is in ± 20% in-30 ℃～160 ℃ specific range of temperatures, wherein, and L/C ^0.5Be the displacement L of described piezoelectric-actuator and the ratio of the square root of described apparent dynamic capacity C,

W _L/C ^0.5(％)＝[{2×(L/C ^0.5) _max/((L/C ^0.5) _max+(L/C ^0.5) _min)}—1]×100

(8)

Wherein, (L/C ^0.5) _MaxBe illustrated in-30 ℃～160 ℃ the interior L/C of specific range of temperatures ^0.5Maximum, (L/C ^0.5) _MinBe illustrated in-30 ℃～160 ℃ the interior L/C of particular range ^0.5Minimum value.

14. piezoelectric-actuator according to claim 10 is characterized in that: also satisfy following important document (n),

(n) by with described piezoelectric-actuator dynamic strain amount that the strain of extra electric field direction is calculated divided by electric field strength in-30 ℃～160 ℃ specific range of temperatures for more than the 250pm/V.

15. piezoelectric-actuator according to claim 10, it is characterized in that: comprise PTC resistor with positive temperature coefficient of resistance, described PTC resistor is electrically connected with the described piezoelectric ceramic with negative temperature coefficient of resistance is in parallel, is configured according to the temperature of described PTC resistor and the temperature position relation about equally of described piezoelectric ceramic simultaneously.

16. piezoelectric-actuator according to claim 15 is characterized in that: described PTC resistor is a barium titanate-base semiconducting, has positive temperature coefficient of resistance in temperature is temperature province more than 80 ℃.

17., it is characterized in that according to claim 1 or 10 described piezoelectric-actuators: described piezoelectric-actuator have stacked by a plurality of described piezoelectric ceramic and the Piezoelektrisches mehrschichtelement that forms as described piezoelectric element, and be used for Fuelinjection nozzle.

18. according to claim 1 or 10 described piezoelectric-actuators, it is characterized in that: described piezoelectric ceramic constitutes by containing the piezoelectric ceramic that is selected from a kind alkali metal containing among Li, K and the Na at least.

19. according to claim 1 or 10 described piezoelectric-actuators, it is characterized in that: described piezoelectric ceramic is not leaded.

20., it is characterized in that according to claim 1 or 10 described piezoelectric-actuators: in described crystal orientation piezoelectric ceramic, described general formula: { Li _x(K _1-yNa _y) _1-x{ Nb _{1-z- w}Ta _zSb _wO ₃In x, y and the z relation that satisfies following formula (9) and formula (10),

9x—5z—17w≥—318 (9)

—18.9x—3.9z—5.8w≤—130 (10)。

21. according to claim 1 or 10 described piezoelectric-actuators, it is characterized in that: cube { degree of orientation of 100} face is more than 30% to the plan that the employing Lao Tegaierdingfa of described crystal orientation piezoelectric ceramic measures, and in 10 ℃～160 ℃ temperature range, crystallization is a regular crystal.

Images