JP3210782B2 - Piezoelectric ceramic composition for actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device for an actuator.
It relates to a porcelain composition .

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric magnetic composition include, for example, a ceramic filter, an ultrasonic transducer, a piezoelectric buzzer, a piezoelectric ignition unit, an ultrasonic motor, a piezoelectric fan, a piezoelectric sensor, and a piezoelectric actuator. .

[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. 32 in Table 2, the piezoelectric strain constant (d ₃₃ constant) is 633 × 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. 32 in FIG. 1, if a load of 1 t / cm ² is repeatedly applied 10 times, the d ₃₃ constant is attenuated by 40 to 50%, which is not suitable for an application in which a large stress is applied. Will be.

An object of the present invention is to provide a piezoelectric ceramic composition which is excellent in piezoelectric strain characteristics, Curie temperature and durability, and is particularly 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 third component that forms a solid solution in rO ₃ -PbTiO ₃ , a composition that becomes Pb (Zn _1/3 Sb _2/3 ) O ₃ was set as the third component , and a part of Pb was replaced with Sr , Ba at least
The present inventors have found that a piezoelectric ceramic composition for an actuator having excellent piezoelectric strain characteristics, Curie temperature, and durability can be obtained by substituting the same with one type, and the present invention has been accomplished.

That is, the piezoelectric ceramic composition for an actuator of the present invention comprises at least Pb, Zr, T
i, Sr, Ba, Zn, a composite perovskite compound including Sb, the composition formula by molar ratio of the metal elements _{Pb 1-xy Sr x Ba y} (Zn 1/3 Sb 2/3) a Zr _b
When expressed as Ti _1-ab O ₃ , x, y, a, and b are 0 ≦ x ≦
0.14, 0 ≦ y ≦ 0.14, 0.04 ≦ x + y , 0.
It satisfies 01 ≦ a ≦ 0.12 and 0.43 ≦ b ≦ 0.58.

Here, the reason why x, y, a, and b are set in the above ranges will be described. Although the substitution of Sr is effective for obtaining an extremely large piezoelectric strain constant d ₃₃ , the substitution amount x is set to 0 ≦ x ≦ 0.14 because if x is larger than 0.14, the Curie temperature sharply increases. This is because the temperature drops below 150 ° C. Further, when the Curie temperature is 200 ° C. or higher due to the substitution of Ba, the piezoelectric strain constant d _{33 is set} to 600 × 10 ⁻¹² m.
/ V can also be at least, is effective to obtain a very high Curie temperature and the piezoelectric strain constant d _33, of the substitution amount y was 0 ≦ y ≦ 0.14 is, y is 0.14 If it is more than the Curie temperature, the Curie temperature is greatly reduced to 150 ° C. or less.

Further, the reason _{why the} substitution amount a of Ti by (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. 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, and when using as a piezoelectric sensor, 0.01 ≦ a ≦ 0.12. it is possible to obtain a large piezoelectric output constant g ₃₃ with a ≦ 0.05.

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 the MPB changes depending on the amounts of x and a, the value of b is set to a composition range in which MPB can be captured within the composition range of x and a. That is, 0.
The reason for setting 43 ≦ b ≦ 0.58 is that M is out of this range.
This is because PB cannot be captured.

The piezoelectric ceramic according to the present invention is, for example, composed of PbO, ZrO ₂ , TiO ₂ , SrCO ₃ , B
aCO ₃ , ZnO and Sb ₂ O ₃ were weighed and mixed, and the mixture was dehydrated and dried.
The calcined product is calcined at 900 ° C. for 1 to 3 hours, and the calcined product is again pulverized by a ball mill or the like.

Thereafter, an organic binder (P
VA) was mixed and granulated. The obtained powder is molded at a predetermined pressure to produce a molded body, and these are molded at 1240 to 1300.
It is obtained by baking at 1 to 3 hours.

[0016]

In the piezoelectric ceramic composition for an actuator of the present invention, a part of Pb is replaced by Sr and Ba, and PbZrO ₃ −
By dissolving the composition of Pb (Zn _1/3 Sb _2/3 ) O _{3 in} PbTiO ₃ as a third component, a high piezoelectric strain characteristic and a high Curie temperature can be obtained, as well as the conventional one. And Pb (Ni _1/3 Nb _2/3 ) O as the third component
_{Since 3} is not used, the attenuation of the piezoelectric strain constant is suppressed even when a constant load is repeatedly applied, and the durability is improved.

[0017]

The present invention will be described below with reference to the following examples. PbO, ZrO ₂ , TiO ₂ , SrCO ₃ ,
Using each powder of BaCO ₃ , ZnO and Sb ₂ O ₃ ,
These were weighed to the ratios 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 t /
At a pressure of ² cm ² , two types of compacts, a disk 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 disk and column were aged at 100 ° 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 , mechanical quality factor Qm, dielectric loss tan δ _E ). The Curie temperature Tc is a temperature at which the relative dielectric constant has a maximum value when a phase transition from a high-temperature side paraelectric property to a low-temperature side ferroelectric phase occurs. Also, the durability, by using a uniaxial hydraulic press machine pressure of 1t / cm ² repeatedly applied at intervals of 1 cycle 4 seconds cylindrical ceramic 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%. Table 1 shows the results.
It is shown in FIG.

[0021]

[Table 1]

[0022]

[Table 2]

In these Tables 1 and 2, the compliance constant s ₃₃ ^{E has} a unit of × 10 ⁻¹² m ² / N, the piezoelectric distortion constant d _{33 has} a unit of × 10 ⁻¹² m / V, and the piezoelectric output constant g ₃₃ has a unit of × 10 ⁻¹² m / V. The unit is × 10 ⁻¹² Vm / N, and the piezoelectric distortion 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.

In Table 1, samples No. 3, 20, 32
1 shows the evaluation of durability.

When the temperature environment in which the piezoelectric actuator is used is 100 ° C. or lower, the Curie temperature needs to be 150 ° C. Often used in such environments, the lower limit of the Curie temperature is 150 ° C.
Although the, according to Table 1, Sample No. 3 while maintaining Curie temperature to a relatively high temperature and 0.99 ° C., the piezoelectric strain constant d ₃₃ is 804 × 10 ^-12 no m / v and another to the class It has an extremely large d constant. As a result of a durability test in which a pressure of 0.5 t / cm ² was repeatedly applied 50 times,
attenuation constant d ₃₃ showed excellent characteristics in durability because there was 5%. Further, when the piezoelectric actuator is used for applications exposed to a high temperature of 100 to 150 ° 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. 19, 20, and 25, the Curie temperature exceeds 200 ° C. and the piezoelectric strain constant d ₃₃ is 600 × 10 ⁻¹² m. A large piezoelectric strain constant exceeding / v is obtained. Furthermore attenuation constant d ₃₃ in the durability test a load of 0.5 t / cm ² is added repeated 50 times since it showed excellent properties as about 3%, there is one very excellent as a piezoelectric actuator material.

As shown in Sample Nos. 26 and 27, Pb
When the solid solution amount a of (Zn _1/3 Sb _2/3 ) O ₃ is smaller than 0.05, the piezoelectric distortion constant d ₃₃ is not so large, but a large piezoelectric output constant g ₃₃ is obtained, and the acceleration sensor and the like can be used. Ideal for piezoelectric sensors.

As described above, 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.
It can also be seen that a large piezoelectric output constant can be obtained.

[0028]

As described in detail above, according to the present invention, P
bO, ZrO ₂ , TiO ₂ , SrCO ₃ , BaCO ₃ , Zn
By mixing O and Sb ₂ O ₃ at a predetermined ratio, the piezoelectric strain constant and Curie temperature are both large, and the decay rate of the piezoelectric strain constant is small even when a load is repeatedly applied, and the durability is excellent. Characteristics can be obtained,
It can be seen that the element has characteristics suitable for a piezoelectric actuator element. Also, a large piezoelectric output constant can be obtained .

[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.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 C04B 35/00 H01B 3/12 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] (1) at least Pb, Zr, T
i, Sr, Ba, Zn, a composite perovskite compound including Sb, the composition formula by molar ratio of the metal elements _{Pb 1-xy Sr x Ba y} (Zn 1/3 Sb 2/3) a Zr _b Ti
_When expressed as _1-ab O ₃ , x, y, a, b are 0 ≦ x ≦ 0.140 0 ≦ y ≦ 0.14 0.04 ≦ x + y 0.01 ≦ a ≦ 0.12 0.43 ≦ A piezoelectric ceramic composition for an actuator, wherein b ≦ 0.58 is satisfied.