JP5011140B2 - Piezoelectric ceramic composition, method for producing the same, and piezoelectric element - Google Patents

Description

  The present invention relates to a piezoelectric ceramic composition that does not contain lead in the composition, a method for producing the same, and a piezoelectric element that uses the piezoelectric ceramic composition as a material.

Conventionally, PZT (PbTiO ₃ —PbZrO ₃ ) component-based porcelain containing lead has been used as a piezoelectric ceramic composition. The above-mentioned PZT has a high mechanical quality factor that exhibits large piezoelectricity and excellent long-term stability, and easily produces materials with various characteristics required for various applications such as sensors, actuators, and filters. Because it can.
Further, since the PZT has a high relative dielectric constant, it can also be used as a capacitor or the like.

However, while the piezoelectric ceramic composition comprising PZT has excellent characteristics, it contains lead as a constituent element, so harmful lead is eluted from industrial waste of products containing PZT, resulting in environmental pollution. There was a risk of causing. The recent increase in awareness of environmental problems has made it difficult to manufacture products that can cause environmental pollution such as PZT. Therefore, development of a piezoelectric ceramic composition that does not contain lead in the composition is required, and a piezoelectric ceramic composition represented by the general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) (See Patent Document 1).

However, since the piezoelectric ceramic composition represented by the general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) is difficult to fire, it is necessary to perform hot press firing. Therefore, there has been a problem that the manufacturing cost becomes high.
Furthermore, the piezoelectric ceramic composition represented by the above general formula has a problem that the characteristics such as the piezoelectric d ₃₁ constant, the electromechanical coupling coefficient Kp, and the Curie temperature Tc are low. Therefore, for example, a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, a piezoelectric ultrasonic motor, a piezoelectric gyro sensor, a knock sensor, a yaw rate sensor, and an airbag sensor that require a high piezoelectric constant d ₃₁ constant and an electromechanical coupling coefficient Kp. It has been difficult to apply to piezoelectric elements such as back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric igniter. In addition, since the Curie temperature Tc is low, there is a problem that the piezoelectric characteristics deteriorate in a high temperature environment.
“Journal of the American Ceramic Society”, USA, 1962, Vol. 45, no. 5, p. 209

The present invention has been made in view of such conventional problems, does not contain lead, can be fired at normal pressure, and has at least one of the characteristics unique to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant. It is an object of the present invention to provide a piezoelectric ceramic composition and method for producing the same, and a piezoelectric element using the piezoelectric ceramic composition.

A first aspect of the present invention is represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a and b are 0 <x ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, and b ≦ 1.05, respectively. The piezoelectric ceramic composition is characterized by being in the composition range of (Claim 1).

The piezoelectric ceramic composition of the first invention, the above general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) as represented by _b O ₃ In addition, the composition does not contain lead.
Therefore, the piezoelectric ceramic composition is safe because harmful lead does not flow out to the natural world from the waste of the piezoelectric ceramic composition.

In the piezoelectric ceramic composition, x, y, z, and w in the above general formula are in the above ranges. Therefore, the piezoelectric ceramic composition is excellent in any one or more of piezoelectric d ₃₁ constant, electromechanical coupling coefficient Kp, piezoelectric g ₃₁ constant, relative dielectric constant ε _33T / ε ₀ , dielectric loss tan δ, and Curie temperature Tc. It will be a thing.

  Further, the piezoelectric ceramic composition has a range of z in the above general formula of 0 <z ≦ 0.4, a range of w of 0 <w <0.06, and contains Ta and Sb as essential components. ing. Therefore, the piezoelectric ceramic composition is easily densified during firing, and can be sufficiently densified even by firing under normal pressure. This is because by using Ta and Sb as essential components within the above range, the firing temperature is lowered, and Ta and Sb serve as a firing aid, enabling firing with less voids. . Therefore, it is not necessary to perform hot press firing as in the prior art, and the piezoelectric ceramic composition can be produced easily and at low cost. In addition, the stability of the dielectric loss tan δ of the piezoelectric ceramic composition can be improved.

Thus, the piezoelectric ceramic composition is safe for the environment, can be fired at normal pressure, and can be used as a material such as a high-performance piezoelectric element or dielectric element.
The piezoelectric ceramic composition according to the first aspect of the present invention is not limited to a ceramic composition having piezoelectric characteristics, but is a concept including a dielectric ceramic composition having dielectric characteristics.

The second invention are represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a and b are 0 <x ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, and b ≦ 1.05, respectively. According to another aspect of the present invention, there is provided a method for producing a piezoelectric ceramic composition, wherein a powder made of the composition in the composition range is molded and fired.

A molded body formed using the powder made of the above composition can be fired under normal pressure. Therefore, firing can be performed easily and at low cost. The piezoelectric ceramic composition obtained after firing does not contain lead and has excellent characteristics unique to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant. Therefore, it can be used as a material such as a high-performance piezoelectric element or dielectric element.

  A third invention includes a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, and a compound containing tantalum. The piezoelectric ceramic composition according to the first aspect of the present invention is obtained by mixing and firing a compound containing antimony (claim 9).

In the third invention, as described above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, and antimony The compound formed is mixed and fired.
Thereby, the piezoelectric ceramic composition of the first invention can be easily obtained.

In the firing, the piezoelectric ceramic composition can be fired under normal pressure. The piezoelectric ceramic composition obtained after firing does not contain lead and has excellent characteristics unique to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant. Therefore, it can be used as a material such as a high-performance piezoelectric element or dielectric element.

  A fourth invention is a piezoelectric element characterized by having the piezoelectric ceramic composition of the first invention (invention 11).

The piezoelectric element of the fourth invention has the piezoelectric ceramic composition of the first invention (Invention 1). Therefore, the piezoelectric element does not contain lead and is safe for the environment.
In addition, the piezoelectric element can use the property of the piezoelectric ceramic composition that is excellent in the characteristics unique to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant. Therefore, the piezoelectric element can be used as an excellent piezoelectric element such as a highly sensitive piezoelectric sensor element, a piezoelectric vibrator having high electromechanical energy conversion efficiency, and an actuator element.

In the present invention, the piezoelectric ceramic composition is represented by _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z , W, a, b are 0 <x ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, b ≦, respectively. It is in the composition range of 1.05.
Here, when x> 0.2, z> 0.4, w> 0.2, z = 0, or w = 0, characteristics unique to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant are obtained. The piezoelectric ceramic composition having the desired characteristics may not be obtained.

As described above, the piezoelectric ceramic composition contains a compound having a perovskite structure (ABO ₃ ) as a main component. In the present invention, the elemental configuration of the A site in the perovskite structure (ABO ₃ ) corresponds to K, Na or K, Na, and Li, and the elemental configuration of the B site corresponds to Nb, Ta, and Sb. In the composition formula of the perovskite structure, when the stoichiometric ratio is 1: 1 for the atoms constituting the A site and the B site, a complete perovskite structure is obtained. In particular, K, Na, Li, and Sb are volatilized by several percent, specifically about 3% in the firing step, etc., or all constituent elements are several percent in the mixed pulverization or granulation step, specifically, May vary by about 3%. That is, variation from the stoichiometric composition may occur due to variations in the manufacturing method.

  As a response to such composition fluctuations in the manufacturing process, by intentionally changing the composition ratio, the composition ratio of the piezoelectric ceramic composition after firing is ± several%, more specifically ± 3-5. % Can be varied. This is also the case with, for example, conventional zirconate titanate (PZT), and the mixing ratio is adjusted in consideration of lead evaporation during firing and zirconia balls from the grinding media. be able to.

In the piezoelectric ceramic composition of the present invention, even if the composition ratio is intentionally changed as described above, electrical characteristics such as piezoelectric characteristics do not change greatly.
Therefore, in the present invention, the compound represented by the above general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -zw} Ta _z Sb _w ) _b O ₃ has a perovskite structure. When the composition formula ABO ₃ is applied, the composition ratio of the A site atom and the B site atom can be shifted to about ± 5 mol% with respect to 1: 1. In order to reduce the number of lattice defects in the formed crystal and obtain high electrical characteristics, the composition is preferably up to about ± 3%.
That is, the compound represented by the above general formula as the main component of the piezoelectric ceramic composition is {Li _x (K _1−y Na _y ) _1−x } _a (Nb _1−zw Ta _z Sb _w ) _b O ₃ (0 <x ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, b ≦ 1.05) Includes a range. As described above, in the above formula, the ranges of a and b are preferably 0.97 ≦ a and b ≦ 1.03.

Similarly, the general formula _{{Li x (K 1-y} Na y) 1-x} In _{a (Nb 1-zw Ta z} Sb w) b O 3, it is preferable that z + w ≦ 0.37.
In this case, characteristics peculiar to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant can be further improved.

  The piezoelectric ceramic composition has a piezoelectric property and a dielectric property, and can be used as a piezoelectric material or a dielectric material. Specifically, for example, piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, It can be used as a piezoelectric igniter.

In the first aspect (claim 1), the scope of the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 of x, It is preferable that 0 <x ≦ 0.2.
In this case, since Li is an essential component, the piezoelectric ceramic composition can more easily produce a fired body at the time of firing, further improve piezoelectric characteristics, and further raise the Curie temperature. be able to. This is because by making Li an essential component within the above range, the firing temperature is lowered, and Li serves as a firing aid, allowing firing with less voids.

Further, the range of the y in the above general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 has to be 0 <y ≦ 1 preferable.
In this case, the piezoelectric g ₃₁ constant of the piezoelectric ceramic composition can be further improved. The range of y is more preferably 0 <y ≦ 0.85, and more preferably 0.05 ≦ y ≦ 0.75. In these cases, the piezoelectric d ₃₁ constant and the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition can be further improved. Still more preferably, 0.05 ≦ y <0.75 is satisfied, 0.35 ≦ y ≦ 0.65 is further preferable, and 0.35 ≦ y <0.65 is more preferable. Most preferably, 0.42 ≦ y ≦ 0.60.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or more.
In this case, taking advantage of the piezoelectric d ₃₁ constant of 30 pm / V or higher, the piezoelectric ceramic composition can be used as a highly sensitive piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor. , Knock sensors, yaw rate sensors, airbag sensors, back sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, piezoelectric igniters, and the like.

When the piezoelectric d ₃₁ constant is less than 30 pm / V, the piezoelectric ceramic composition may not be used for a piezoelectric element that requires excellent sensitivity.
In order to obtain more sensitive piezoelectric sensor characteristics or larger piezoelectric actuator characteristics, the piezoelectric d ₃₁ constant is more preferably 40 pm / V or more. More preferably, it is 80 pm / V or more. More preferably, the piezoelectric d ₃₁ constant is 100 pm / V or more.

Next, the piezoelectric ceramic composition preferably has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more.
In this case, the piezoelectric ceramic composition is used as a piezoelectric transformer, an ultrasonic motor element, a sensor element or the like having an excellent step-up ratio by utilizing the high piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more. be able to.

When the piezoelectric g ₃₁ constant is less than 7 × 10 ⁻³ Vm / N, the piezoelectric ceramic composition may not be used for a piezoelectric element that requires an excellent step-up ratio.
In order to obtain a further excellent boost ratio, the piezoelectric g ₃₁ constant is more preferably 10 × 10 ⁻³ Vm / N or more.

Next, the piezoelectric ceramic composition preferably has an electromechanical coupling coefficient Kp of 0.3 or more.
In this case, utilizing the high electromechanical coupling coefficient Kp of 0.3 or more, the piezoelectric ceramic composition is converted into a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer having excellent mechanical energy and electric energy conversion efficiency. It can be used as a piezoelectric ultrasonic motor, a piezoelectric gyro sensor, a knock sensor, a yaw rate sensor, an airbag sensor, a back sonar, a corner sonar, a piezoelectric buzzer, a piezoelectric speaker, a piezoelectric igniter, and the like.

When the electromechanical coupling coefficient Kp is less than 0.3, the piezoelectric ceramic composition may not be used for a piezoelectric element that requires excellent conversion efficiency between the mechanical energy and the electrical energy. .
Further, in order to obtain a further excellent conversion efficiency between mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably 0.34 or more. More preferably, 0.4 or more is good. More preferably, the electromechanical coupling coefficient Kp is 0.5 or more.

Next, the piezoelectric ceramic composition preferably has a dielectric loss of 0.09 or less.
In this case, taking advantage of the low dielectric loss of 0.09 or less, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor, piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor. , Knock sensors, yaw rate sensors, airbag sensors, back sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, piezoelectric igniters and the like.

When the dielectric loss exceeds 0.09, the piezoelectric ceramic composition may not be used as a dielectric element such as a capacitor, a piezoelectric transformer element, or an ultrasonic motor element.
The dielectric loss is more preferably 0.035 or less.

Next, it is preferable that the piezoelectric ceramic composition has a relative dielectric constant of 400 or more.
In this case, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor having a large electrostatic capacity by utilizing the high relative dielectric constant of 400 or more.
When the relative dielectric constant is less than 400, the capacitance decreases, and the piezoelectric ceramic composition may not be used as a dielectric element such as a capacitor.
The relative dielectric constant is more preferably 430 or more. More preferably, 600 or more is good.

Next, the piezoelectric ceramic composition preferably has a Curie temperature Tc of 200 ° C. or higher.
In this case, utilizing the high Curie temperature Tc of 200 ° C. or higher, the piezoelectric ceramic composition can be used in a high temperature environment exceeding 100 ° C., for example, in the vicinity of an automobile engine.
When the Curie temperature Tc is less than 200 ° C., the piezoelectric ceramic composition decreases in characteristics such as the piezoelectric d ₃₁ constant and the electromechanical coupling coefficient Kp when used in a hot place such as the vicinity of an automobile engine. There is a risk.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or higher and a Curie temperature Tc of 200 ° C. or higher.
In this case, the piezoelectric ceramic composition can be used as a highly sensitive sensor element, ultrasonic motor element, actuator element, piezoelectric transformer element, piezoelectric vibrator, etc. in a high temperature environment exceeding 100 ° C. .
In order to obtain more sensitive piezoelectric sensor characteristics or greater piezoelectric actuator characteristics, the piezoelectric d ₃₁ constant is preferably 40 pm / V or more. More preferably, it is 80 pm / V or more. More preferably, the piezoelectric d ₃₁ constant is 100 pm / V or more.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more and a Curie temperature Tc of 200 ° C. or more.
In this case, the piezoelectric ceramic composition can be used as a piezoelectric transformer, an ultrasonic motor element, a sensor element or the like having an excellent step-up ratio in a high temperature environment exceeding 100 ° C.
In order to obtain a further excellent boost ratio, the piezoelectric g ₃₁ constant is more preferably 10 × 10 ⁻³ Vm / N or more.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has an electromechanical coupling coefficient Kp of 0.3 or more and a Curie temperature Tc of 200 ° C. or more.
In this case, in a high temperature environment exceeding 100 ° C., the piezoelectric ceramic composition is excellent in the conversion efficiency of mechanical energy and electrical energy, piezoelectric actuator element, piezoelectric vibrator, sensor element, piezoelectric transformer element, ultrasonic wave It can be used as a motor element or the like.
Further, in order to obtain a further excellent conversion efficiency between mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably 0.34 or more. More preferably, 0.4 or more is good.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a dielectric loss of 0.09 or less and a Curie temperature Tc of 200 ° C. or higher.
In this case, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor, a piezoelectric transformer element, an ultrasonic motor element, a sensor element or the like in a high temperature environment exceeding 100 ° C.
The dielectric loss is more preferably 0.035 or less.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or more, an electromechanical coupling coefficient Kp of 0.3 or more, and a Curie temperature Tc of 200 ° C. or more. 7).
In this case, the piezoelectric ceramic composition can be used in a high temperature environment exceeding a temperature of 100 ° C., and can be excellent in sensitivity and conversion efficiency between mechanical energy and electric energy.
In order to obtain more sensitive piezoelectric sensor characteristics or greater piezoelectric actuator characteristics, the piezoelectric d ₃₁ constant is more preferably 40 pm / V or more. The electromechanical coupling coefficient Kp is more preferably 0.34 or more.

In the third invention (invention 9), examples of the lithium-containing compound include Li ₂ CO ₃ , Li ₂ O, LiNO ₃ , and LiOH. Examples of the compound containing sodium include Na ₂ CO ₃ , NaHCO ₃ , and NaNO ₃ .

Examples of the compound containing potassium include K ₂ CO ₃ , KNO ₃ , KNbO ₃ , and KTaO ₃ . Examples of the compound containing niobium include Nb ₂ O ₅ , Nb ₂ O ₃ , and NbO ₂ . Examples of the compound containing tantalum include Ta ₂ O ₅ . Examples of the compound containing antimony include Sb ₂ O ₅ , Sb ₂ O ₃ , and Sb ₂ O ₄ .

Next, the compound containing lithium is Li ₂ CO ₃ , the compound containing sodium is Na ₂ CO ₃ , the compound containing potassium is K ₂ CO ₃ , and contains niobium. The compound formed is Nb ₂ O ₅ , the compound containing 0 tantalum is Ta ₂ O ₅ , and the compound containing antimony is Sb ₂ O ₅ or Sb ₂ O _3. Preferred (claim 10).
In this case, the piezoelectric ceramic composition can be easily produced.

  Next, in the fourth invention (invention 11), examples of the piezoelectric element include a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, a piezoelectric ultrasonic motor, a piezoelectric gyro sensor, a knock sensor, a yaw rate sensor, There are airbag sensors, back sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, piezoelectric igniters and the like.

  Examples of the dielectric element include a capacitor and a multilayer capacitor.

(Example)
Next, the piezoelectric ceramic composition concerning the Example of this invention is demonstrated.
In this example, the piezoelectric ceramic composition is manufactured and its characteristics are measured.
The piezoelectric ceramic composition of this example is represented by the general formula {Li _x (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ and x, y, z, w Are in the composition ranges of 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z0.4, and 0 <w ≦ 0.2, respectively.

Hereinafter, the manufacturing method of the piezoelectric ceramic composition of this example will be described.
First, high purity Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₅ having a purity of 99% or more were prepared as raw materials for the piezoelectric ceramic composition. .
In these materials the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, x, y, z, w is 0 ≦ x ≦ 0. 2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2.

Here, as shown in Table 1 to Table 6 described later, as x, x = 0, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.10, It was set to 0.15 and 0.20.
Further, y is y = 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.42, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.58, 0.6, 0.70, 0. 75, 0.8 and 1.0.
Further, z is such that z = 0.002, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.30. I made it.
In addition, w was set to w = 0.02, 0.04, 0.05, 0.06, 0.07, 0.1, 0.2.
And the raw material mix | blended so that it might become each stoichiometric composition was mixed in acetone for 24 hours with the ball mill, and the mixture was produced.

Next, the mixture was calcined at 750 ° C. for 5 hours, and the calcined mixture was pulverized for 24 hours by a ball mill. Subsequently, polyvinyl butyral was added as a binder and granulated.
The granulated powder was pressure-molded into a disk shape having a diameter of 18 mm and a thickness of 1 mm at a pressure of ² ton / cm ² , and this molded body was fired at 1000 to 1300 ° C. for 1 hour to produce a fired body. . In addition, the temperature which becomes the maximum density between 1000 degreeC-1300 degreeC was selected for the calcination temperature at this time. In addition, all of the fired bodies were densified to a relative density of 98% or more.

Next, both surfaces of each fired body after firing were subjected to parallel polishing and circular polishing, and then gold electrodes were provided on both surfaces of this disk sample by sputtering. And the direct-current voltage of 1-5 kV / mm was applied between electrodes for 10 minutes in 100 degreeC silicone oil, and it polarized in the thickness direction, and was set as the piezoelectric ceramic composition.
Thus, piezoelectric ceramic compositions (samples 1 to 182) having 182 stoichiometric compositions were produced. Tables 1 to 6 show the chemical composition ratio of each sample.

Moreover, in this example, in order to clarify the excellent characteristics of the piezoelectric ceramic composition, comparative products 1 to 5 were produced as follows.
First, high-purity K ₂ CO ₃ , Na ₂ CO ₃ and Nb ₂ O ₅ having a purity of 99% or more were prepared as raw materials for the comparative product 1.
These raw materials and the general formula (K _0.5 Na _0.5 ) NbO ₃ were mixed at a stoichiometric ratio and mixed in acetone for 24 hours by a ball mill to obtain a mixture.
This mixture was calcined, granulated, molded, fired and polarized in the same manner as Samples 1 to 182 described above to obtain Comparative Product 1.

Further, high purity Li ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and Sb ₂ O ₅ having a purity of 99% or more were prepared, and comparative products 2, 3, 4, and as 5, in the _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) composition formula, respectively x = 0.22, y = 0.50, z = 0.45, w = 0.22, and x = 0.22, y = 0.50, z = 0.10, w = 0.02, and x = 0.02, y = 0.50, z = Samples having 0.45, w = 0.02, x = 0.02, y = 0.50, z = 0.10, and w = 0.22 were produced by the same method.
Table 6 shows the chemical composition ratios of the comparative products 1 to 5.

Next, the piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant, the electromechanical coupling coefficient Kp, the Curie temperature Tc, the relative dielectric constant ε _33T / ε ₀ , and the dielectric loss tan δ are measured for the samples 1 to 182 and the comparative products 1 to 5. did.

Here, the piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant, and the electromechanical coupling coefficient Kp were measured by a resonance-antiresonance method using an impedance analyzer.
The dielectric loss and relative dielectric constant were measured at a measurement frequency of 1 kHz using an impedance analyzer.
The Curie temperature Tc was defined as the Curie temperature Tc that is the temperature at which the relative dielectric constant is the highest.
The results are shown in Tables 7-12.

  The samples 2, 4, 5, 8, 15, 16, 31 to 34, 40, 41, 48, 49, 71, 72, 74, 75, 79, 80, 81, 88 to 90, 103, 104, 107, 110, 112, 115, 118, 119, 123-129, 133, 134, 136-140, 143, 145, 151, 152 and comparative product 1 were measured for long-term stability of dielectric loss.

As a method for measuring the long-term stability of the dielectric loss, first, the dielectric loss tan δ of the sample after polarization and the comparative product 1 is measured at a measurement frequency of 1 kHz using an impedance analyzer in the same manner as described above. The initial tan δ was used. Furthermore, the long-term stability of dielectric loss was evaluated by measuring dielectric loss tan δ after 50 days, 100 days, or 200 days from the polarization and comparing it with the initial tan δ value.
The results are shown in Tables 13-14.

As is known from Tables 6 to 12, Samples 1 to 13, 15 to 20, 25 to 28, 31 to 37, 39 to 44, 46 to 52, 55 to 59, 67, 71 to 85, 87 to 92, 97 ～99,103～154,156～159,162～182 showed higher than comparative product first piezoelectric d ₃₁ constant.
Here, the sample 155 to the sample 180 in Table 12 are x, z and w in the general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } (Nb _{1 -zw} Ta _z Sb _w ) O ₃ . FIG. 4 shows various piezoelectric characteristics and dielectric characteristics when the value of y is fixed and the value of y is changed. In Sample 155～ sample 180 to reveal a change in the piezoelectric d ₃₁ constant when changing the value of y, for values of the piezoelectric d ₃₁ constant when the y = 0.5 (Sample 158), the sample The ratio of the piezoelectric d ₃₁ constant values of 155 to 180 is shown as the d ₃₁ ratio.

  Moreover, as is known from Tables 6-12, Samples 1-5, 7-12, 15-20, 25-28, 31-36, 39-44, 47-51, 56-58, 71-78, 80- 84, 88 to 90, 103 to 154, 157 to 159, and 164 to 179 showed an electromechanical coupling coefficient Kp higher than that of the comparative product 1.

In addition, Samples 1 to 159 and Samples 162 to 182 exhibited a high relative dielectric constant of 430 or more, and were superior to Comparative Product 1.
Samples 1-5, 7-12, 16-20, 31-34, 40-42, 47-50, 58, 65, 71-77, 80-82, 103-111, 115, 118-130, 134 , 136～139,158,160～161,165～166,168～169,171,173,175, and sample from 179 to 180 showed a high piezoelectric g ₃₁ constant that 7.0 × 10 ^-3 or more.

Samples 1 to 22, 24 to 54, 58 to 62, 70 to 86, 89 to 94, and 101 to 180 exhibited a high Curie temperature Tc of 200 ° C. or higher.
Samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 182 exhibited low dielectric loss tan δ of 0.09 or less.

  Further, as is known from Table 13 and Table 14, the dielectric loss of each sample was excellent in stability without significantly increasing even after 50 days, 100 days, or 200 days. On the other hand, the dielectric loss of the comparative product 1 increased by 3 times the initial tan δ after 50 days and exceeded 6 times after 100 days. Further, after 200 days, it increased to nearly 7 times the initial tan δ, and there was a problem in stability.

Here, paying attention to the piezoelectric d ₃₁ constant, as is known from Tables 1 to 12, x = 0.04, y = 0.54, z = 0.1, and w = 0.06 (sample 175). The piezoelectric d ₃₁ constant showed the highest value of 132.4 pm / V.

Further, as is known from Table 6 and Table 12, in the above general formula Li _x (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ , the value of y is changed. It can be seen that the piezoelectric d ₃₁ constant changes greatly when the piezoelectric ceramic composition is manufactured.
Therefore, in order to make the relationship between the value of y in the above general formula and the piezoelectric d ₃₁ constant easier to understand, the result of the piezoelectric d ₃₁ constant in Table 12 is shown in FIG. In FIG. 1, the horizontal axis indicates the value of y in the above general formula, and the vertical axis indicates the piezoelectric d ₃₁ constant.

As known from FIG. 1, in order to realize a high piezoelectric d ₃₁ constant of 40 pm / V or more, the above general formula Li _x (K _{1 -y} Na _y ) _1-x } (Nb _{1 -zw} Ta _z Sb _w It can be seen that the value of y in O ₃ is preferably 0.05 ≦ y <0.75. Further, when the value range of y is 0.35 ≦ y ≦ 0.65, a higher piezoelectric d ₃₁ constant of 80 pm / V or more can be realized. Furthermore, when the value range of y is 0.42 ≦ y ≦ 0.60, a much higher piezoelectric d ₃₁ constant exceeding 100 pm / V can be realized. However, the preferable range of the value of y changes when the values of x, z, and w in the general formula change.

When a charge detection type circuit or a current detection type circuit is used, the piezoelectric d ₃₁ constant is generally
It is proportional to the output voltage of a piezoelectric sensor such as an acceleration sensor, a weight sensor, an impact sensor, or a knock sensor. From this point of view, a piezoelectric ceramic composition having a higher piezoelectric d ₃₁ constant can produce a sensor element having a larger charge sensor output. In order to manufacture a sensor element having characteristics equal to or higher than those of the comparative product 1, it can be said that it is preferable to have a piezoelectric d ₃₁ constant of at least 30 pm / V. Furthermore, in order to increase the signal-to-noise ratio (SN ratio) and the output voltage to produce a highly sensitive sensor element, the piezoelectric d ₃₁ constant is preferably 80 pm / V or more. More preferably, it is 100 pm / V or more.

When used as an actuator, the piezoelectric d ₃₁ constant is generally proportional to the generated strain or displacement of the piezoelectric actuator. From this point of view, a piezoelectric ceramic composition having a higher piezoelectric d ₃₁ constant can produce an actuator element having a larger generated strain or displacement. In order to produce an actuator element having characteristics equal to or higher than those of the comparative product 1, it can be said that it is preferable to have a piezoelectric d ₃₁ constant of at least 30 pm / V. More preferably, it is 40 pm / V or more. In order to manufacture an actuator with a larger displacement, the piezoelectric d ₃₁ constant is preferably 80 pm / V or more. More preferably, it is 100 pm / V or more.

  When attention is paid to the electromechanical coupling coefficient Kp, as is known from Tables 1 to 12, when x = 0, y = 0.5, z = 0.002, and w = 0.04 (sample 31), The electromechanical coupling coefficient Kp showed the highest value of 0.623.

  In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer. From this point of view, a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer having a higher electromechanical energy conversion efficiency can be produced with a piezoelectric ceramic composition having a higher electromechanical coupling coefficient Kp. In order to manufacture a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer having characteristics equal to or higher than those of the comparative product 1, the electromechanical coupling coefficient Kp must be at least 0.3 or more. It can be said that it is preferable. More preferably 0.34 or more. More preferably, 0.4 or more is good. Further, more preferably 0.5 or more.

Further, when paying attention to the Curie temperature Tc, the Curie temperature Tc of the piezoelectric ceramic compositions of Samples 1-22, 24-54, 58-62, 70-86, 89-94, 101-180 is a high value of 200 ° C. or higher. Have taken. Therefore, the piezoelectric ceramic composition of the present example in the above composition region is, for example, a sensor component for high temperature such as a knock sensor that can be used stably for a long time even in a high temperature part near the engine of an automobile, an actuator component, It can be used as an ultrasonic motor component.
In addition, the Curie temperature Tc is preferably 200 ° C. or higher in order to use the sensor component, the actuator component, the ultrasonic motor component and the like for the high temperature stably for a long time. More preferably, the temperature is 250 ° C. or higher.

Further, when attention is paid to the piezoelectric g ₃₁ constant, as is known from Tables 1 to 12, x = 0, y = 0.
. 5, z = 0.002, and w = 0.04 (sample 31), the piezoelectric g ₃₁ constant is 16.
The highest value of 2 × 10 ⁻³ Vm / N was shown.

The piezoelectric g ₃₁ constant is proportional to the output voltage of a piezoelectric sensor, a piezoelectric transformer element, an ultrasonic motor element, or the like, like the piezoelectric d ₃₁ constant. Therefore, a piezoelectric ceramic composition having a higher piezoelectric g ₃₁ constant can produce a sensor having a larger voltage sensor output. And it can be said that it is preferable to have a piezoelectric g ₃₁ constant of at least 7 × 10 ⁻³ Vm / N or more in order to produce a sensor having characteristics equal to or higher than those of the comparative product 1. More preferably, it is 10 × 10 ⁻³ Vm / N or more.

Moreover, focusing on the dielectric constant ε _33T / ε _0, the relative dielectric constant ε _33T / ε ₀ of the sample 1 to 159 and the sample 162 to 182 takes the high value of 430 or more.

The relative dielectric constant ε _33T / ε ₀ is generally proportional to the capacitance of a capacitor such as a multilayer capacitor component. From this point of view, a piezoelectric ceramic composition having a higher relative dielectric constant can produce a capacitor having a larger capacitance. In order to produce a capacitor, it can be said that it is preferable to have a relative dielectric constant of at least 400 or more. More preferably, 430 or more is good. More preferably, 600 or more are good.

  Further, when attention is paid to the dielectric loss tan δ, the dielectric loss tan δ of the samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 182 has a low value of 0.09 or less. .

  The dielectric loss is proportional to the thermal energy lost when an AC voltage is applied to a component such as a capacitor component, a piezoelectric ultrasonic motor, a piezoelectric actuator, or a piezoelectric transformer. From this point of view, the piezoelectric ceramic composition having a smaller dielectric loss can produce a capacitor with less energy loss and a piezoelectric ultrasonic motor, piezoelectric actuator, and piezoelectric transformer with less heat generation. And in order to produce the said components with little energy loss, it is preferable to have a dielectric loss of 0.09 or less. More preferably, it is 0.035 or less.

Further, paying attention to the long-term stability of dielectric loss, as shown in Tables 13 and 14, when Z = 0.002, that is, a sample with a very low Ta content, the dielectric loss becomes large when left in the atmosphere for a long time. There is a drawback of becoming. On the other hand, in the sample with z> 0.002 and w ≠ 0, the change in dielectric loss is small even when left in the atmosphere for a long time, and the value of dielectric loss is kept as small as 0.09 or less. Thus, in the above general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } (Nb _{1 -zw} Ta _z Sb _w ) O ₃ shown in the present invention, 0 ≦ x ≦ 0.2, The dielectric loss tan δ of the piezoelectric ceramic composition of this example in the composition ranges of 0 ≦ y ≦ 0.1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2 has long-term stability.

Further, as shown in Table 12, the comparative products 2, 3 and 5 which are not included in the composition region of the piezoelectric ceramic composition of the present invention have piezoelectric d ₃₁ constants of 0.5, 9.81 and 13.31 pm / It was found that both V and the value were low. Further, it was found that the comparative product 4 has a piezoelectric d ₃₁ constant of 42.62 pm / V, but has a Curie temperature as low as 117 ° C. and cannot be used as an automotive part requiring a Curie temperature of 200 ° C. or higher.

According to the embodiment, explanation diagram showing the relationship of the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) value of y in the O ₃ and the piezoelectric d ₃₁ constant .

Claims (11)

It is represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a, b are respectively 0 <X ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, b ≦ 1.05 A piezoelectric ceramic composition characterized by the above.   The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a Curie temperature Tc of 200 ° C or higher. 3. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric d ₃₁ constant of 30 pm / V or more. 4. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more. 5. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric d ₃₁ constant of 30 pm / V or more and a Curie temperature Tc of 200 ° C. or more. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more and a Curie temperature Tc of 200 ° C. or more. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric d ₃₁ constant is 30 pm / V or more, the electromechanical coupling coefficient Kp is 0.3 or more, and the Curie temperature Tc is 200 ° C. or more. Piezoelectric ceramic composition. It is represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a, b are respectively 0 <X ≦ 0.2, 0.05 ≦ y <0.75 , 0 <z ≦ 0.4, 0 <w <0.06, 0.95 ≦ a, b ≦ 1.05 A method for producing a piezoelectric ceramic composition, characterized by molding and firing a powder made of a product.   A compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and an antimony A method for producing a piezoelectric ceramic composition according to any one of claims 1 to 7, wherein the piezoelectric ceramic composition according to any one of claims 1 to 7 is obtained by mixing and firing the compound. 10. The compound containing lithium according to claim 9, wherein the compound containing lithium is Li ₂ CO ₃ , the compound containing sodium is Na ₂ CO ₃ , the compound containing potassium is K ₂ CO ₃ , and niobium The compound containing Nb ₂ O ₅ is, the compound containing tantalum is Ta ₂ O ₅ , and the compound containing antimony is Sb ₂ O ₅ or Sb ₂ O _3. A method for producing a piezoelectric ceramic composition.   A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1.

Images