JPH08175867A - Piezoelectric composition - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a piezoelectric ceramic composition having a large piezoelectric output constant g ₃₁ and excellent heat resistance.
For example, a piezoelectric ceramic composition suitable for a piezoelectric sensor such as an acceleration sensor, a knocking sensor, and an AE sensor is provided. [Composition] The composition formula based on the atomic ratio of metallic elements is Pb _1-xy
Sr _x La _y (Y _1/2 Nb _1/2 ) _a (Cr _1/3 S
b _2/3 ) _b Zr _c Ti _{1 -abc} O ₃ to 100 parts by weight of the main component, a Cr-containing compound is added in an amount of z parts by weight in terms of Cr ₂ O ₃ , and the x, y, z, a,
b and c are 0.01 ≦ x ≦ 0.04, 0.005 ≦
y ≦ 0.02, 0 ≦ z ≦ 0.5, 0.003 ≦ a ≦ 0.
04, 0 ≦ b ≦ 0.03, 0.53 ≦ c ≦ 0.62,
It satisfies 0.003 ≦ a + b ≦ 0.05 (where 0.01 ≦ b when z = 0 and 0 ≦ b when z> 0).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition, for example, a piezoelectric sensor such as an acceleration sensor, a knocking sensor, an AE sensor or the like, a ceramics filter, an ultrasonic wave applied vibrator, a piezoelectric buzzer, a piezoelectric ignition unit, an ultra-high-speed unit. The present invention relates to a piezoelectric ceramic composition suitable for a sound wave motor, a piezoelectric fan, a piezoelectric actuator, and the like.

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric ceramic composition include, for example, acceleration sensors, knocking sensors,
Piezoelectric sensors such as AE sensors and ceramic filters,
There are ultrasonic transducers, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, and piezoelectric actuators.

Piezoelectric sensors such as acceleration sensors, knocking sensors, and AE sensors are sensors that utilize the function of converting so-called mechanical energy, which generates electric charges when a force is applied to a piezoelectric element, into electrical energy. . Piezoelectric sensors are solid-state devices that utilize the piezoelectric effect, so compared to conventional strain gauges and magnetostrictive sensors,
It is compact and highly sensitive, and has the characteristics of excellent temperature characteristics, and also has the characteristics that the cost can be significantly reduced compared to a semiconductor sensor using a silicon single crystal or the like. Therefore, along with the sophistication of electronics and mechatronics, research and development in various fields such as electronic control of suspensions of automobiles and vibration control of electronic devices are being advanced.

By the way, as the use of the above-mentioned sensor expands, a highly sensitive characteristic is required to improve control performance, so that a larger piezoelectric output constant g ₃₁ is required, and further, it is mounted on a vehicle. In use, etc.
Since it may be used in a severe environment exceeding 120 ° C, there is a demand for a piezoelectric ceramic composition having excellent heat resistance that does not deteriorate in characteristics even when left at a temperature of 120 to 200 ° C.

Conventionally, as a piezoelectric ceramic composition having a large piezoelectric output constant g ₃₁ which meets the purpose of a piezoelectric sensor, for example, one disclosed in Japanese Patent Laid-Open No. 6-183834 is known. The piezoelectric ceramic composition disclosed in this publication is so-called PLZT in which a part of Pb of Pb (ZrTi) O ₃ is replaced with La, and the piezoelectric output constant g ₃₁ is about 1 ×.
It has good characteristics showing 10 ^-2 Vm / N. Also,
In order to improve heat resistance, it has been proposed to add MnO to PLZT, for example.

[0006]

However, in the above-mentioned piezoelectric ceramic composition to which MnO is not added, although a large piezoelectric output constant g ₃₁ can be obtained, the heat resistance is poor,
Even when MnO is added, the temperature is 120 to 200 ° C.
There was a problem that the heat resistance was still low when exposed to the constant temperature. Further, when MnO is added, the piezoelectric output constant g ₃₁ becomes extremely small, which causes a problem that the application is limited.

[0007]

An object of the present invention is to provide a piezoelectric ceramic composition having a large piezoelectric output constant g ₃₁ and excellent heat resistance, and in particular, for example, an acceleration sensor, a knocking sensor, an AE sensor, etc. An object of the present invention is to provide an optimal piezoelectric ceramic composition for the piezoelectric sensor of.

[0008]

The inventors of the present invention conducted a search for an optimum component which forms a solid solution with PbZrO ₃ --PbTiO ₃ which is the first and second components, and as a result, Pb (Y _1/2 N
b _1/2 ) O ₃ and Pb (Cr _1/3 Sb _2/3 ) O ₃ are dissolved as third and fourth components, and a part of Pb is replaced with Sr and La to form Cr. It has been found that a piezoelectric ceramic composition excellent in piezoelectric output constant g ₃₁ and heat resistance can be obtained by adding an appropriate amount of ₂ O ₃ and the present invention has been completed.

That is, the piezoelectric ceramic composition of the present invention contains at least Pb, Zr, Ti, Y, Nb and C as metal components.
A compound perovskite type compound containing r, Sb, Sr and La, wherein the composition formula based on the atomic ratio of these metal elements is: Pb _1-xy Sr _x La _y (Y _1/2 Nb _1/2 ) _a (Cr
_1/3 Sb _2/3 ) _b Zr _c Ti _{1 -abc} O ₃ to 100 parts by weight of the main component, a Cr-containing compound is added in an amount of z parts by weight in terms of Cr ₂ O _3. , Y, z, a, b and c are 0.01 ≦ x ≦ 0.
04, 0.005 ≦ y ≦ 0.02, 0 ≦ z ≦ 0.5,
0.003 ≦ a ≦ 0.04, 0 ≦ b ≦ 0.03, 0.5
3 ≦ c ≦ 0.62, 0.003 ≦ a + b ≦ 0.05 (however, 0.01 ≦ b when z = 0, 0 ≦ b when z> 0)
Is satisfied.

Now, the reason why the Cr ₂ O ₃ substitution amount z of the x, y, a, b, c and Cr-containing compounds is set within the above range will be described.

The replacement of Pb with Sr is effective for obtaining a large piezoelectric output constant g ₃₁ , but the replacement amount x is set to 0.
01 ≦ x ≦ 0.04 means that when x is larger than 0.04, the heat resistance is lowered and the piezoelectric output constant g ₃₁ is 1 ×.
This is because it becomes smaller than 10 ^-2 Vm / N. Also, if x is smaller than 0.01, the effect of improving the piezoelectric output constant g ₃₁ cannot be obtained. The substitution amount x of Sr is 0.02 to 0.
It is desirable that it is 03.

Further, the replacement of Pb with La is effective for obtaining a larger piezoelectric output constant g ₃₁ , but the replacement amount y is set to 0.005 ≦ y ≦ 0.02 because y is 0. ．
This is because if it is greater than 02, the heat resistance is significantly reduced.
If it is less than 0.005, the desired piezoelectric output constant g ₃₁
Because I can't get it. The substitution amount y of La is 0.005
It is desirable to be 0.01.

The replacement of Ti with (Y _1/2 Nb _1/2 ) has the effect of increasing the piezoelectric output constant g ₃₁ while maintaining the Curie temperature at a high temperature. The substitution amount a is 0.00
The reason for 3 ≦ a ≦ 0.04 is that when a is larger than 0.04, the heat resistance is lowered and the piezoelectric output constant g ₃₁ is deteriorated. Also, if the substitution amount a is less than 0.003, the effect of improving the piezoelectric output constant g ₃₁ cannot be obtained. The substitution amount a of Ti by (Y _1/2 Nb _1/2 ) is 0.01 ≦ a ≦
It is preferably 0.02.

Further, replacement of Ti with (Cr _1/3 Sb _2/3 ) improves the heat resistance without raising the mechanical quality factor Qm so much that useful properties for a wide band sensor can be obtained. The reason that the amount b is 0 ≦ b ≦ 0.03 is that when the substitution amount b is larger than 0.03, the desired heat resistance cannot be obtained together with the decrease of the Curie temperature.

If the substitution amount b is smaller than 0.01, the mechanical quality factor Qm tends to decrease,
The substitution amount b of (Cr _1/3 Sb _2/3 ) is 0.01 ≦ b ≦ 0.
It is desirable to set it to 03.

On the other hand, since the heat resistance of the porcelain itself can be improved to some extent by adding a Cr-containing compound, when the substitution amount b of Ti by (Cr _1/3 Sb _2/3 ) is 0, the Cr content is increased. The heat resistance may be improved by adding a compound. A composition in which Ti is replaced by (Cr _1/3 Sb _2/3 ) and a Cr-containing compound is further added is an optimal composition in terms of improving heat resistance.

Incidentally, the addition of the Cr-containing compound makes the mechanical quality factor Qm remarkably large, which is a useful property for a resonance type sensor. Therefore, the substitution of (Cr _1/3 Sb _2/3 ) or the addition of the Cr-containing compound may be selected according to the detection signal and the detection method.

Further, the Cr-containing compound is added so that the amount z of Cr ₂ O ₃ conversion is 0 ≦ z ≦ 0.5 parts by weight with respect to 100 parts by weight of the above-mentioned main component in order to improve heat resistance. Is. When the Cr ₂ O ₃ conversion amount z of the Cr-containing compound is more than 0.5 parts by weight, the piezoelectric output constant g
_{This is because 31} is smaller than 1 × 10 ^-2 Vm / N.

[0019] However, when terms of Cr ₂ O ₃ amount z of Cr-containing compound is a 0, it is necessary that the substitution amount b is 0.01 or more _{(Cr 1/3 Sb 2/3)} . This is because when z is 0 and the substitution amount b of (Cr _1/3 Sb _2/3 ) is smaller than 0.01, the heat resistance becomes insufficient.

The Cr ₂ O ₃ conversion amount z of the Cr-containing compound is preferably 0.1 ≦ z ≦ 0.25 parts by weight.
As the Cr-containing compound, metal Cr, Cr ₂ O ₃ , Cr
There are O ₂ and Cr ₃ O ₈ .

Further, 0.003≤a + b≤0.05 is set because (Y _1/2 Nb _1/2 ) and (Cr _1/3 Sb) of Ti.
_This is because when the total amount a + b of the substitution amount of _2/3 ) exceeds 0.05, the heat resistance decreases.

A piezoelectric ceramic composition containing PZT as a main component,
When the solid solution ratio of PbZrO ₃ and PbTiO ₃ is changed, there exists MPB (composition phase boundary) in which the relative permittivity and electromechanical coupling coefficient show maximum values. As the piezoelectric sensor material, a composition value having a high electromechanical coupling coefficient and a steeply decreasing relative dielectric constant in a composition region containing more PbZrO ₃ than MPB is used. The value of c is 0.53 ≦ c
The reason for setting ≦ 0.62 is that if it is smaller than 0.53, the MPB region is captured, and not only a large piezoelectric output constant g ₃₁ cannot be obtained, but also the heat resistance becomes insufficient. On the other hand, if it is larger than 0.62, the desired piezoelectric output constant g ₃₁ cannot be obtained.

The piezoelectric ceramic composition of the present invention has a composition formula based on the atomic ratio of metal elements as Pb _1-xy Sr _x La _y (Y _1/2
Nb _1/2 ) _a (Cr _1/3 Sb _2/3 ) _b Zr _c Ti
When expressed as _1-abc O ₃ , x, y, a, b and c are
0.02 ≦ x ≦ 0.03, 0.005 ≦ y ≦ 0.01,
0.01 ≦ a ≦ 0.02, 0.01 ≦ b ≦ 0.02,
0.003 ≦ a + b ≦ 0.05, 0.53 ≦ c ≦ 0.6
It is desirable to add 0.1 to 0.25 parts by weight of Cr-containing compound in terms of Cr ₂ O ₃ to 100 parts by weight of the main component satisfying 2.

The piezoelectric ceramic according to the present invention may be prepared, for example, by using PbO, ZrO ₂ , TiO ₂ , SrC as raw material powder.
O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Nb ₂ O ₅ , Cr ₂ O ₃
And Sb ₂ O ₅ powders are weighed and mixed. This mixture is calcined at a temperature of 900 to 1000 ° C., and the calcined product is crushed. Then, a Cr-containing compound is optionally added to the pulverized product and an organic binder or the like is added and mixed, and the mixture is molded into a predetermined shape by, for example, press molding, and fired at 1200 to 1300 ° C. for 1 to 5 hours in a lead atmosphere, A piezoelectric ceramic is obtained by performing polarization processing.

[0025]

In the piezoelectric ceramic composition of the present invention, a part of Pb is S
Substitution with r and La to give PbZrO ₃ —PbTiO ₃ ,
Pb (Y _1/2 Nb _1/2 ) O ₃ and Pb (Cr _1/3 Sb _{2 /
3} ) A solid solution having a composition of O ₃ as the third and fourth components, and by adding an appropriate amount of Cr ₂ O ₃ to this basic component, a large piezoelectric output constant g exceeding 1 × 10 ^-2 Vm / N is obtained.
₃₁ is obtained, and even if it is left for a long time in a constant temperature, the piezoelectric output constant g ₃₁ is not deteriorated, and excellent heat resistance is obtained.

[0026]

The present invention will be described in the following examples. As raw material powder, PbO, ZrO ₂ , TiO ₂ , SrC
O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Nb ₂ O ₅ , Cr ₂ O ₃
And Sb ₂ O ₅ powders were weighed so as to have the compositions shown in Table 1, and wet mixed in a ball mill for 24 hours. Then, after dehydrating and drying this mixture,
It was calcined at a temperature of 50 ° C., and the calcined product was wet pulverized again with a ball mill for 24 hours. Then, Cr ₂ O ₃ was added to the pulverized product in an amount shown in Table 1, an organic binder (PVA) was mixed, and granulated. 1.5 of the powder obtained
A disk having a diameter of 23 mm and a thickness of 3 mm was produced at a pressure of ton / cm ² and these were subjected to 1 atmosphere in a lead atmosphere.
It was baked at 250 ° C. for 3 hours. The obtained sintered body was cut into a rectangular shape having a length of 12 mm, a width of 3 mm, and a thickness of 1 mm, and silver electrodes were baked on both sides of 12 mm × 3 mm, respectively, and then in silicon oil at 80 ° C.
Polarization was performed by applying a DC voltage of 5 kV / mm or more. Place the polarized sample in a constant temperature bath at 220 ° C.
After aging for an hour, it was left for 24 hours. From the thus obtained porcelain, the piezoelectric output constant g ₃₁ was examined based on the standardized measuring method of the Electronic Material Industries Association (EMAS).

The heat resistance is 100 at a constant temperature of 200.degree.
It was determined by measuring the retention rate of the piezoelectric output constant g ₃₁ after standing for a time. Here, a retention rate of 95% or more was rated as O, and a retention rate of less than 95% was rated as X. Table 1 shows the results.

[0028]

[Table 1]

From Table 1, in the piezoelectric ceramic composition of the present invention, the piezoelectric output constant g ₃₁ is 1 × 10 ⁻² Vm / N or more, and the retention rate of the piezoelectric output constant g ₃₁ showing heat resistance is 95% or more. It can be seen that it exhibits excellent characteristics.

FIG. 1 shows samples Nos. 5 and 27 in Table 1.
Evaluation of heat resistance of is shown. From this figure, the comparative example No.
The sample No. 27 has a piezoelectric output constant g ₃₁ that decreases with time, whereas the sample No. 5 of the present invention has a piezoelectric output constant g ₃₁ of almost the same even when left for 100 hours in a constant temperature of 200 ° C. It can be seen that the retention rate does not change.

That is, for example, when the piezoelectric sensor is used near or in contact with an automobile engine, 1
Although it is required that the piezoelectric ceramic composition of Sample No. 5 has a piezoelectric output constant g ₃₁ of 16 × 10 ^−, it is required that the characteristics are not deteriorated even at a high temperature of 20 to 200 ° C. and that it is excellent in heat resistance. ^It has an extremely large value of ³ Vm / N, which is unparalleled, and shows excellent heat resistance with no deterioration of properties even when left at 100 ° C for 100 hours. There is.

[0032]

As described above in detail, the piezoelectric ceramic composition of the present invention can obtain a large piezoelectric output constant g ₃₁ exceeding 1 × 10 ^-2 Vm / N and can be left at high temperature for a long time. Since the piezoelectric output constant g ₃₁ does not deteriorate in characteristics and exhibits excellent heat resistance, it can be suitably used as a piezoelectric material for a piezoelectric sensor element.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the retention rate of piezoelectric output constant g ₃₁ and time at a constant temperature of 200 ° C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiko Onizuka 1-4 Yamashita-cho, Kokubun-shi, Kagoshima Kyocera Stock Company Research Institute (72) Inventor Kenichi Yoshimura 1-4-4 Yamashita-cho, Kokubun-shi, Kagoshima Kyocera Corporation Shikisha Research Institute

Claims (1)

[Claims] 1. At least Pb, Zr, T as a metal component.
A compound perovskite type compound containing i, Y, Nb, Cr, Sb, Sr and La, wherein the composition formula based on the atomic ratio of these metal elements is: Pb _1-xy Sr _x La _y (Y _1/2 Nb _{1 / 2} ) _a (Cr
_1/3 Sb _2/3 ) _b Zr _c Ti _{1 -abc} O ₃ to 100 parts by weight of the main component, a Cr-containing compound is added in an amount of z parts by weight in terms of Cr ₂ O _3. , Y, z, a, b and c satisfy the following conditions: a piezoelectric ceramic composition. 0.01 ≤ x ≤ 0.04 0.005 ≤ y ≤ 0.02 0 ≤ z ≤ 0.5 0.003 ≤ a ≤ 0.04 0 ≤ b ≤ 0.03 0.53 ≤ c ≤ 0.62 0.003 ≦ a + b ≦ 0.05 (however, if z = 0, 0.01 ≦ b; if z> 0, 0 ≦
b)