JP2922769B2 - Piezoelectric ceramic composition for actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic composition for an actuator.

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric ceramic composition include, for example, ceramic filters, ultrasonic applied vibrators, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, piezoelectric sensors, and piezoelectric actuators. .

[0003] Here, the piezoelectric actuator uses displacement or force generated through a piezoelectric phenomenon as a mechanical drive source, and is one of the things that have recently attracted attention in the field of mechatronics. Piezoelectric actuators are solid-state elements that utilize the piezoelectric effect, and therefore consume less power, have a faster response speed, have a larger displacement, and generate more heat than conventional electromagnetic actuators that have a coil wound around a magnetic material. And has excellent features such as small size and small weight. For this reason, research and development in various fields have been promoted with the advancement of mechatronics.

[0004] By the way, as the applications of the above-mentioned actuator have been expanded, a larger mechanical displacement is required, and it is necessary to be able to withstand use in a wide temperature range (-30 to 150 ° C). I have. That is, a high Curie temperature is desired. In general, the piezoelectric element has a piezoelectric strain constant, particularly d ₃₃ , because of its function as an actuator element.
It is desirable that the constant be as large as possible. in this way,
The characteristics of piezoelectric materials suitable for piezoelectric actuator applications are:
The quality of the material can be determined by various constants (electromechanical coupling coefficient, dielectric constant, piezoelectric strain constant, etc.) and Curie temperature which are usually used in this kind of material.

As a piezoelectric ceramic composition meeting such a purpose, Pb (Ni _1/3 Nb _2/3 ) O ₃ is added to a PZT system.
Some are substituted as components. For example, Pb (Ni
_1/3 Nb _2/3 ) _0.50 Zr _0.15 Ti _0.35 O _{3. In} this example, as shown in Sample No. 19 in Table 1, the piezoelectric strain constant (d ₃₃ constant) is 620 × 10 ⁻¹² m. / V.

[0006]

However, in the case where the above PZT system in which Pb (Ni _1/3 Nb _2/3 ) O ₃ is substituted as the third component is used for a piezoelectric actuator, Low Curie temperature (Tc)
There was a problem that it could not be used in an environment exposed to a high temperature of 0 to 150 ° C. Thus, in this composition system, those having a large piezoelectric strain constant have a low Curie temperature,
There is a disadvantage that the use as a displacement element is limited to an extremely narrow range.

In addition, since the actuator is always subjected to a compressive stress, in the case of an actuator application, attenuation of the piezoelectric strain constant, that is, durability is a problem. However, in the above composition, the attenuation of the piezoelectric strain constant is large. However, there is a problem that durability is poor. That is, as can be seen from the curve of Sample No. 19 in FIG. 1, when a load of 1 ton / cm ² is repeatedly applied 10 times, the d ₃₃ constant is attenuated by 40 to 55%.
This is not suitable for applications where large stress is applied. Further, a large attenuation of the piezoelectric strain constant under a compressive stress means that a state change of the ferroelectric domain structure is apt to occur, which also causes an increase in displacement hysteresis. That is, the sample No. 19 of FIG.
As can be seen from the displacement hysteresis curve, 100 V / m
Since the displacement hysteresis generated when m is applied exceeds 10%, the resolution is degraded, and it is not suitable for positioning applications.

An object of the present invention is to provide a piezoelectric ceramic composition for an actuator which is excellent in piezoelectric strain characteristics, Curie temperature, durability and displacement hysteresis and is suitable for a piezoelectric actuator.

[0009]

[Means for Solving the Problems] The present inventors have proposed PbZ
As a result of searching for an optimal component that forms a solid solution in rO ₃ -PbTiO ₃ , Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb
(Ni _1/2 Te _1/2 ) O ₃ is dissolved in a predetermined amount as the third and fourth components to form a solid solution, so that the actuator is excellent in piezoelectric strain characteristics, Curie temperature, durability and displacement hysteresis. The present inventors have found that a piezoelectric ceramic composition can be obtained, and have reached the present invention.

That is, the piezoelectric ceramic composition for an actuator of the present invention comprises Pb, Zr, Ti, Zn, S
b, Ni, Te and a composite perovskite compound containing Sr and / or Ba, the Pb _1-xy formula by molar ratio of the metal elements Sr _x Ba _y (Zn
_{1/3 Sb 2/3) a (Ni 1/2} Te 1/2) b Zr c Ti
_When expressed as _1-abc O ₃ , x, y, a, b, and c are 0
≦ x ≦ 0.14, 0 ≦ y ≦ 0.14, 0 <x + y, 0.
01 ≦ a ≦ 0.12, 0.002 ≦ b ≦ 0.020,
0.43 ≦ c ≦ 0.58 is satisfied.

Here, the reason why x, y, a, b, and c are set in the above ranges will be described.

Substitution of Sr results in an extremely large piezoelectric strain constant d ₃₃
Is effective to obtain the following, but the substitution amount x is 0 ≦ x ≦ 0.
The reason for setting the value to 14 is that when x is more than 0.14, the Curie temperature sharply drops, and is much lower than 150 ° C.
It is desirable that the replacement amount x of Sr is 0.04 ≦ x ≦ 0.12.

The Curie temperature is reduced to 2 by Ba substitution.
At a temperature of 00 ° C. or more, the piezoelectric strain constant d _{33 is set} to 600 × 10 ⁻¹² m / v.
This is effective for obtaining an extremely high Curie temperature and a piezoelectric distortion constant d ₃₃ , but the substitution amount y
Is set to 0 ≦ y ≦ 0.14 because if y is more than 0.14, the Curie temperature is greatly reduced to 150 ° C. or less. The substitution amount y of Ba is 0.02 ≦ y ≦ 0.1
It is desirably 2.

The reason _{why the} substitution amount a of Ti with (Zn _1/3 Sb _2/3 ) is set to 0.01 ≦ a ≦ 0.12 is that the larger the value of a, the larger the piezoelectric strain constant is obtained, This is a useful property. If conversely a small, large piezoelectric output constant g ₃₃ useful in piezoelectric sensors such as an acceleration sensor is obtained. However, a can not be a piezoelectric strain constant d ₃₃ less than 0.01 400 × 10 ^-12 m / v or more, since the change over time or temperature change of the piezoelectric output constant g ₃₃ increases The reason for this is that the piezoelectric sensor lacks usefulness. If a is larger than 0.12, the Curie temperature is greatly reduced, and the dielectric loss is very large. The substitution amount a of Ti with (Zn _1/3 Sb _2/3 ) is preferably 0.05 ≦ a ≦ 0.10.

When the piezoelectric ceramic composition of the present invention is used as a piezoelectric actuator, a large piezoelectric strain constant can be obtained by setting 0.05 ≦ a ≦ 0.12. .01 ≦ a ≦ 0.05
It is possible to obtain a large piezoelectric output constant g ₃₃ With.

The reason why the substitution amount b of Ti with (Ni _1/2 Te _1/2 ) is set to 0.002 ≦ b ≦ 0.020 is as follows.
When b is large, it has very excellent characteristics in durability and displacement hysteresis. However, when b is larger than 0.020, deterioration of piezoelectric characteristics due to aging at 130 ° C. becomes remarkably large, and piezoelectric strain constant a d ₃₃ 400 ×
This is because it cannot be made 10 ^-12 m / V or more.
If b is smaller than 0.002, there is almost no effect on improving the durability and the characteristics of displacement hysteresis. The substitution amount b of Ti with (Ni _1/2 Te _1/2 ) is 0.
It is desirable that 002 ≦ b ≦ 0.007.

A piezoelectric ceramic composition containing PZT as a main component is
When the solid solution ratio between PbZrO ₃ and PbTiO ₃ is changed, there is an MPB (composition phase boundary) showing the maximum value of the piezoelectric strain constant. As the piezoelectric actuator material, this MPB and the composition value in the vicinity thereof are used. Since this MPB changes depending on the amount of x, a, b, the value of c is x, a, b
The composition range where MPB can be captured within the composition range of b. That is, the reason for setting 0.43 ≦ c ≦ 0.58 is that if c is out of this range, MPB cannot be captured.

The piezoelectric ceramic according to the present invention is, for example, composed of PbO, ZrO ₂ , TiO ₂ , SrCO ₃ , B
Each powder of aCO ₃ , ZnO, Sb ₂ O ₃ , NiO and TeO ₂ was weighed and mixed, then the mixture was dehydrated and dried, and then calcined at 850 to 900 ° C. for 1 to 3 hours. Pulverize again with a ball mill or the like.

Then, an organic binder (P
VA) was mixed and granulated. The obtained powder is molded at a predetermined pressure to prepare a molded body, and the molded body is fired at 1240 to 1300 ° C. for 1 to 3 hours in a lead atmosphere.

[0020]

In the piezoelectric ceramic composition of the present invention, a part of Pb is S
r, Ba, and PbZrO ₃ -PbTiO ₃
b (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te
By dissolving the composition which becomes _1/2 ) O ₃ as the third and fourth components, high piezoelectric strain characteristics, small displacement hysteresis, and high Curie temperature can be obtained. As Pb (Ni _1/3 Nb _2/3 )
Since O ₃ is not used, even when a constant load is repeatedly applied, attenuation of the piezoelectric strain constant is suppressed, durability is improved,
Displacement hysteresis is reduced.

[0021]

The present invention will be described below with reference to the following examples. PbO, ZrO ₂ , TiO ₂ , SrCO ₃ ,
BaCO ₃ , ZnO, Sb ₂ O ₃ , NiO and TeO ₂
These powders were weighed in the proportions shown in Tables 1 and 2 and wet-mixed for 24 hours in a ball mill. Next, after dehydrating and drying this mixture, it was calcined at 870 ° C. for 3 hours, and the calcined product was again wet-pulverized by a ball mill for 24 hours.

Thereafter, an organic binder (P
VA) was mixed and granulated. 1.5 to
At a pressure of n / cm ² , two types of compacts, a disc having a diameter of 23 mm and a thickness of 3 mm and a column having a diameter of 8 mm and a thickness of 18 mm, were produced. Further, these were fired at 1270 ° C. for 3 hours.

The obtained sintered body is 20 mm in diameter and 1 m in thickness.
polished into a disk with a diameter of 6 mm and a column with a diameter of 6 mm and a thickness of 15 mm, baking silver electrodes on both sides, and applying a DC voltage of 1.5 kv / mm or more in silicon oil at 80 ° C. to perform polarization processing. went.

The polarized disks and cylinders were aged at a constant temperature of 120 ° C. for 1 hour and then left for 24 hours.
From each of the thus obtained porcelains, piezoelectric constants (electromechanical coupling coefficient K ₃₃ , relative dielectric constant ε ₃₃ ^T / ε) were obtained based on a standardized measurement method of the Electronic Materials Industries Association (EMAS).
₀ , compliance constant s ₃₃ ^E , piezoelectric strain constant d ₃₃ , and dielectric loss tan δ _E ).

The Curie temperature Tc is a temperature at which the relative dielectric constant at the time of a phase transition from a high-temperature side paraelectric property to a low-temperature side ferroelectric phase is maximized. Also, the durability, by using a uniaxial hydraulic press repeatedly applying a pressure of 1 ton / cm ² into a cylindrical porcelain at intervals of 1 cycle 4 seconds, was determined by measuring the retention of the piezoelectric strain constant d ₃₃ . Here, the attenuation factor of the piezoelectric strain constant d ₃₃ is the ○ those within 20% in the case of adding the repeated pressure 10 times, and as × when it exceeds 20%.

Furthermore, displacement hysteresis was measured by measuring the displacement in the polarization direction when a voltage of 100 V was applied to the disc-shaped sample using a non-contact optical sensor. Here, the displacement hysteresis is expressed as a ratio of the difference between the displacement generated at the time of 1/2 applied voltage (50 V) and the displacement generated at the time of falling voltage with respect to the displacement generated at the maximum applied voltage (100 V). When the displacement hysteresis exceeded 10%, the result was indicated by x, 10 to 7% was indicated by Δ, and less than 7% was indicated by ○. Table 1 shows the results.

[0027]

[Table 1]

In Table 1, the unit of the compliance constant s ₃₃ ^E is × 10 ⁻¹² m ² / N, the unit of the piezoelectric strain constant d ₃₃ is × 10 ⁻¹² m / V, and the unit of the piezoelectric output constant g ₃₃ is ×.
10 ⁻¹² Vm / N, and the piezoelectric strain constant d ₃₃ and the piezoelectric output constant g ₃₃ are respectively d ₃₃ = K ₃₃ (ε ₃₃ ^T · s ₃₃ ^E ).
^1/2 , g ₃₃ = d ₃₃ / ε ₃₃ ^T. The durability of the samples Nos. 1, 3, 4, and 19 in Table 1 was evaluated as shown in FIG.
Shown in

When the temperature environment in which the piezoelectric actuator is used is 100 ° C. or less, the Curie temperature needs to be 150 ° C. Often used in such environments, the lower limit of the Curie temperature is 150 ° C.
According to Table 1, it is necessary that the sample No. 3 has a Curie temperature as high as 177 ° C. and a piezoelectric strain constant d ₃₃ of 725 × 10 ⁻¹² m / v. It has an unusually large d constant. 0.5t
the pressure of the on / cm ² 50 times repeatedly adding results of the test for durability, attenuation constant d ₃₃ showed excellent characteristics in durability since it was 2%.

Further, from the characteristics of the displacement generated by applying a voltage, the displacement hysteresis is 5.4% and the displacement characteristics are excellent due to the excellent linearity. Further, when the piezoelectric actuator is 100 to 150
When used in applications exposed to high temperatures of up to 200 ° C., the Curie temperature needs to exceed 200 ° C. In the case of an actuator material, it is desired that the d ₃₃ constant is as large as possible from the viewpoint of its function. For Sample Nos. 6 and 7, the Curie temperature is 200 ° C. and the piezoelectric strain constant d ₃₃ is 600 × 1.
A large piezoelectric strain constant exceeding 0 ^-12 m / v is obtained. Furthermore a load of 0.5 ton / cm ² since the attenuation constant d ₃₃ in the durability test applying repeated 50 times showed about 2% and excellent characteristics, is very excellent as a piezoelectric actuator material. Further, since the displacement hysteresis is 7% or less, it is very excellent as a positioning element.

Further, as shown in sample No. 18, Pb (Zn
_When the solid solution amount a of _1/3 Sb _2/3 ) O ₃ is smaller than 0.05, the piezoelectric strain constant d ₃₃ is not so large, but a large piezoelectric output constant g ₃₃ is obtained, and a piezoelectric sensor such as an acceleration sensor is obtained. Ideal for Further, since the hysteresis associated with the ferroelectric domain shift is small, the output voltage characteristics with respect to the application of stress are linear, and some sensor materials are very excellent.

Thus, the product of the present invention has a large piezoelectric strain constant d.
It is possible to obtain ₃₃ and a high Curie temperature, the attenuation factor of the piezoelectric strain constant d ₃₃ even when applying repeated load is seen to have a very small excellent characteristics.
Further, it can be seen that the displacement hysteresis is extremely small and has excellent characteristics. It can also be seen that a large piezoelectric output constant can be obtained.

[0033]

As described in detail above, according to the present invention, P
bO, ZrO ₂ , TiO ₂ , SrCO ₃ , BaCO ₃ ,
By mixing ZnO, Sb ₂ O ₃ , NiO, and TeO ₂ at a predetermined ratio, the piezoelectric strain constant and Curie temperature are large, and even when a load is repeatedly applied, the piezoelectric strain constant has a small attenuation rate and is durable. Excellent characteristics can be obtained, and the displacement hysteresis is small, indicating that the device has characteristics suitable for a piezoelectric actuator element. Further, since a large piezoelectric output constant is obtained, excellent characteristics can be obtained also in a piezoelectric sensor such as an acceleration sensor, a knocking sensor, and an AE sensor.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of times of repeated pressurization and the holding ratio of a piezoelectric strain constant.

FIG. 2 is a graph showing the relationship between applied voltage and generated displacement in sample No. 3.

FIG. 3 is a graph showing the relationship between applied voltage and generated displacement in sample No. 19.

Continuation of the front page (56) References JP-A-50-26099 (JP, A) JP-A-49-27897 (JP, A) JP-A-56-115586 (JP, A) JP-A-7-315923 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/42-35/49 H01B 3/00-3/14 H01L 41/18-41/187 CA (STN) REGISTRY (STN )

Claims (1)

(57) [Claims] 1. A metal element comprising Pb, Zr, Ti, Zn,
Sb, Ni, Te and a composite perovskite compound containing Sr and / or Ba, the Pb _1-xy formula by molar ratio of the metal elements Sr _x Ba _y (Zn
_{1/3 Sb 2/3) a (Ni 1/2} Te 1/2) b Zr c Ti
_When expressed as _1-abc O ₃ , x, y, a, b, and c are: 0 ≦ x ≦ 0.140 0 ≦ y ≦ 0.140 0 <x + y0.01 ≦ a ≦ 0.12 0.002 ≦ b ≦ 0.020 0.43 ≦ c ≦ 0.58. A piezoelectric ceramic composition for an actuator, characterized by satisfying the following condition.