JP2000327418A - Piezoelectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric porcelain composition capable of obtaining an element having >200×1012 m/v piezoelectric strain constant (d31) of mode of vibration due to elongation in the major side direction and a sufficiently high Curie temperature, less liable to the deterioration of displacement as an actuator and having high grain boundary strength. SOLUTION: At least one selected form W, Sb, Nb and Ta is added as a subsidiary component to Pbx[(CO1/3Nb2/3)aTiBZr1-a-b]O3 (where 0.98<=x<=0.999, 0.01<=a<=0.03 and 0.43<=b<=0.49) as a principal component by 0.1-1.2 wt.% (expressed in terms of WO3, Sb2O3, Nb2O5 and Ta2O5) based on 1 mol principal component and Si is further added as a subsidiary component by 0.01-0.1 wt.% (expressed in terms of SiO2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic composition containing lead zirconate titanate as a main component, and particularly to a piezoelectric actuator having a high piezoelectric strain constant, excellent durability, and excellent grain boundary strength. The present invention relates to a piezoelectric ceramic composition suitable for

[0002]

2. Description of the Related Art Conventionally, the pressure used for this kind of application has been
As the porcelain composition, PbTiO_Three-PbZrO_Threesystem
Are known. For example, PbTiO _Three-PbZ
rO_ThreeSb for system material_TwoO_Five , Nb_TwoO_Five, WO_ThreeSuch
, PbTiO_Three-PbZrO_ThreeSystem material
Pb partially substituted with Ba, Sr, Ca, La
And Pb (Ni_1/3Nb_2/3) O_Three, P
b (Mg _1/3Nb_2/3) O_ThreeCompound perovskite
A solid solution of a compound is known.

[0003]

For example, when a piezoelectric ceramic composition is used for a piezoelectric actuator (hereinafter simply referred to as an actuator), the piezoelectric ceramic composition has a high piezoelectric strain constant (for example, a piezoelectric strain in a long-side stretching vibration mode). Constant (d3
1) is 200 × 10 ⁻¹² m / v or more) and the mechanical quality factor (Qm) is low (for example, 100 or less).

In general, a porcelain composition having a high piezoelectric strain constant is characterized by a low Curie temperature (Tc) (Tc <230 ° C.). For example, a conventionally known piezoelectric strain constant (d31) in the long-side direction elongation vibration mode is 200 × 10
^{When the} piezoelectric ceramic composition exceeds ⁻¹² m / v, the Curie temperature becomes about 200 ° C., and in an environment where the temperature reaches 150 ° C. to 200 ° C., the piezoelectric characteristics are rapidly lowered, so that it may not be practical. Also, the piezoelectric distortion constant (d31) is high,
Piezoelectric ceramic compositions having a low mechanical quality factor (Qm) and a relatively high Curie temperature are also known. However, when these are used as actuators at a temperature of about 150 ° C., there is a problem that displacement deterioration is large.

In addition, when a conventionally known piezoelectric ceramic composition having a high piezoelectric strain constant (d31 ≧ 200 × 10 ⁻¹² m / v) is used for a laminated actuator, the particle size is large and the interlayer is thin. There is a problem that it is difficult to form a laminate (for example, 10 μm or less). Further, there is a problem that the grain boundary strength is weak, cracks and chipping defects are apt to occur during processing of the actuator, and cracks are liable to occur when the actuator is driven.

Accordingly, in the present invention, in order to solve these problems, the piezoelectric strain constant (d3
1) exceeds 200 × 10 ⁻¹² m / v, the Curie temperature is sufficiently high, the degradation of displacement as an actuator is small, and an object is to provide a piezoelectric ceramic composition capable of obtaining an element having high grain boundary strength. It is assumed that.

[0007]

In order to achieve the above object,
Therefore, in the present invention, Pbx [(Co_1/3Nb_2/3) A T
ib Zr1-ab] O_Three(However, 0.98 ≦ x ≦
0.999, 0.01 ≦ a ≦ 0.03, 0.43 ≦ b ≦
0.49) as the main component, and based on 1 mol of the main component,
At least one of W, Sb, Nb, and Ta as a subcomponent
Seeds WO_Three, Sb_TwoO_Three, Nb_TwoO_Five, Ta_TwoO_FiveConvert to
0.1 to 1.2% by weight, and
Si to SiO_Two0.01 to 0.1% by weight
And the Pbx [(Co_1/3Nb
_2/3) A Tib Zr1-ab] O_Three(However, 0.
98 ≦ x ≦ 0.999, 0.01 ≦ a ≦ 0.03, 0.
41 ≦ b ≦ 0.48) as a main component, and a part of Pb is S
at least one of r and Ba is 0.01 to 0.06 m
ol-substituted, as an accessory component to 1 mole of the main component
WO, Sb, Nb, Ta at least one of WO _Three,
Sb_TwoO_Three, Nb_TwoO_Five, Ta_TwoO_FiveConverted to 0.1
To 1.2% by weight, and Si as a subcomponent
O_Two0.01% to 0.1% by weight of piezoelectric
Container composition.

With this configuration, a piezoelectric ceramic having a sufficiently high Curie temperature and a piezoelectric strain constant (d31) of 200 × 10 ⁻¹² m / v in the long-side extension vibration mode can be obtained.
There is no problem in use at a temperature of about 50 ° C., and it is possible to manufacture an actuator with few cracks and chips during processing.

[0009] Lead zirconate titanate contains P as a third component.
By adding b (Co _1/3 Nb _2/3 ) O ₃ , deterioration when the constituted actuator is used at a high temperature (around 150 ° C.) can be reduced.

[0010] In addition, W, Sb, Nb, Ta
At least one of them is WO_Three, Sb _TwoO_Three, Nb
_TwoO_Five, Ta_TwoO_FiveTo the weight of 1 mole of the main component
And 0.1 to 1.2% by weight of the piezoelectric strain constant
And the particle size after firing is smaller.
It is possible to do.

Further, as a subcomponent, Si is converted to SiO ₂ and 0.01 to 0.1% by weight based on 1 mol of the main component.
By adding, the bonding force between the particles in the piezoelectric ceramic can be increased, and as a result, cracks and chips during processing can be reduced, and cracks during driving when an actuator is configured can be reduced. Becomes

By substituting 0.01 to 0.06 mol of at least one of Sr and Ba for part of Pb, the piezoelectric strain constant can be further increased without impairing the above-mentioned advantages.

[0013]

Embodiments of the present invention will be described. Chemically pure PbO, TiO ₂ ,
ZrO ₂ , CoO, Nb ₂ O ₅ , Sb ₂ O ₃ , Ta ₂ O
₅ , WO ₃ , BaCO ₃ , and SrCO ₃ were weighed so that the components after firing had the predetermined compositions shown in Tables 1 and 2, and were wet-mixed with a ball mill. Then, the mixed powder was calcined at 850 ° C. to 950 ° C. in the air, and then wet-pulverized by a ball mill.

Next, an organic binder was added to the powder thus obtained, and granulation was performed, followed by molding at a pressure of 2000 kg / cm ² . This molded body is placed in an air atmosphere for 110 minutes.
Baking was performed at a temperature of 0 ° C to 1240 ° C.

[0015] The sintered body obtained in this way has a thickness of 1 m.
After polishing to 2 m, silver printed electrodes were formed on both ends of the obtained device, and then processed into a rectangle of 12 × 3 mm in length and width, and 80 ° C. to 1 ° C.
In insulating oil at 50 ° C, voltage 2 kv / mm to 3 kv / m
Polarization was performed under the conditions of m and 30 minutes.

The obtained evaluation element was measured for element capacitance (c), resonance frequency (fr), and anti-resonance frequency (fa) using an impedance analyzer. Based on the measurement results, a voltage distortion constant (d31) and a mechanical quality factor (Qm) were calculated. Tables 1 and 2 show the results obtained by the above method.

The Curie temperature was measured using a thermal analyzer.

The state of the particles and the fracture surface of the piezoelectric ceramic substrate was observed with a scanning electron microscope.

As a measurement of the degree of displacement deterioration due to high temperature, a multilayer actuator (interlayer: 20 μm-20 layers—length and width: 15 μm)
× 2.5 mm), and subjected to a high-temperature load test in which a DC rectangular wave having a thickness of 2 kv / mm with respect to the interlayer thickness was applied at a temperature of 150 ° C. The displacement of the element before the test and after the continuous test for 250 hours was measured by a displacement meter, and the rate of change of the displacement was measured from the difference. The results are shown in Tables 1 and 2. It can be determined that the closer the value is to zero, the better the durability of the element. In Tables 1 and 2, an asterisk is a comparative example outside the scope of the present invention.

[0020]

[Table 1]

[0021]

[Table 2]

Each numerical limitation in the present invention is based on the following reasons.

When x is smaller than 0.98, the piezoelectric strain constant (d31) becomes smaller than desired, and the rate of change in displacement after the high-temperature load test also increases (see Sample Nos. 1 and 27).

FIG. 1 shows A and B A: Pbx [(Co _1/3 Nb _2/3 ) _0.015 Ti _0.47 Zr in FIG.
_0.515 ] O ₃ + Sb ₂ O ₃ 0.6 wt% + SiO ₂
05 wt% B: (PbxSr _0.03 ) [(Co _1/3 Nb _2/3 ) _0.015
Ti _0.46 Zr _0.525 ] O ₃ + Sb ₂ O ₃ 0.6 wt% +
The results of a three-point bending strength test when the value is changed in a piezoelectric ceramic composition having a composition of 0.05 wt% of SiO ₂ are shown. As is clear from FIG. 1, when x is 0.98 to 0.999, the three-point bending strength shows a value larger than 12 (kgf / mm ² ), and x becomes smaller than 0.98. In the case and when x is larger than 0.999, the strength decreases.

When a is smaller than 0.01, the rate of change of displacement becomes large, and the effect of preventing displacement deterioration due to high temperature load cannot be obtained (see Sample Nos. 5, 31).

Conversely, when a is larger than 0.03, the mechanical quality factor (Qm) increases and the piezoelectric strain constant also decreases (see Sample Nos. 8 and 34).

In the case where one of Ba and Sr is not included, if b is smaller than 0.43, the piezoelectric strain constant becomes smaller and the mechanical quality coefficient becomes larger (sample No.
23), and when b is larger than 0.49,
Also, the piezoelectric strain constant becomes smaller and the mechanical quality factor becomes larger (see Sample No. 26).

When at least one of Ba and Sr is included, if b is smaller than 0.41, the piezoelectric strain constant becomes smaller and the mechanical quality factor becomes larger (see Sample No. 56). When it is larger than 0.48, the piezoelectric strain constant becomes smaller, and the mechanical quality factor also becomes larger (see Sample No. 59).

When the content of the subcomponent is at least one of W, Sb, Nb and Ta relative to 1 mol of the main component,
_{3, Sb 2 O 3, Nb} 2 O 5, ( see Sample Nanba9,35) piezoelectric constant becomes smaller in the case of Ta less than ₂ O ₅ in terms of 0.1% by weight, 1.2 to reverse If it exceeds 10% by weight, the piezoelectric strain constant becomes small and the deterioration of the displacement after the high temperature load test becomes large (see Sample Nos. 12 and 38).

FIG. 2 shows a sample No. 1 according to an embodiment of the present invention. 1
3 is an electron micrograph showing the polished surface of the sample No. 1 etched. 9 is an electron micrograph of the same observation.

It can be seen that the particle size in FIG. 2 showing the example of the present invention is less than half that of FIG. 3 showing the comparative example, and the particle size of the example is more uniform than in the comparative example. From this comparison, it is clear that the effect of adding the auxiliary component in the present invention is to make the particle system finer and more uniform.

The same effect can be obtained when a part of Pb is replaced with at least one of Ba and Sr.

FIG. 4 shows sample No. 1 according to an embodiment of the present invention. 1
5 is an electron micrograph of the fracture surface of the element, and FIG. 15 is an electron micrograph of a fractured surface of an element manufactured by the same method as in the example of the present invention, with the amount of SiO ₂ added being zero.

When SiO _{2 as a} subcomponent is present,
In the case of FIG. 4 for the example of the present invention, the shape of the particles is hardly seen on the fracture surface, and it can be seen that the particles are broken within the particles. This means that the bonding force between the particles is strong.

On the other hand, as a comparative example, SiO
_In the case of FIG. 5 where ₂ was not added, the shape of the particles was clear, and it can be seen that the fracture occurred at the grain boundary.
This means that the bonding force between the particles is weak. As described above, the effect of adding the sub-component SiO ₂ is apparent from the comparison between FIG. 4 and FIG.

The same effect can be obtained when a part of Pb is replaced with at least one of Ba and Sr.

The reason why Si is limited to 0.01 to 0.1% by weight in terms of SiO ₂ as a subcomponent is that if less than 0.01% by weight, there is no effect of the present invention that the bonding force between particles is strong. (See FIG. 4 and FIG. 5) When it exceeds 0.1% by weight, the piezoelectric strain constant becomes as small as 200 × 10 ⁻¹² m / v or less, and the displacement deterioration after the high temperature load test also becomes large (in absolute value, 2%). This is because the reliability is poor if over 0.0%.
o. 14, 40).

By the way, when a part of Pb is replaced with at least one of Ba and Sr, if the amount is less than 0.01 mol, the effect of increasing the piezoelectric strain constant cannot be obtained (compared to Sample Nos. 44 and 45). By reference, N
o. It can be seen that when 0.01 mol of Sr is added to 44, the piezoelectric strain constant increases from 200 to 235 (× 10 ⁻¹² m / v)), and the effect of reducing the amount of Pb evaporation during firing cannot be obtained.

On the other hand, when the content exceeds 0.06 mol, the displacement deterioration after the high temperature load test becomes large (see Sample No. 47).

The measurement by the thermal analyzer revealed that all the piezoelectric ceramic compositions of this example had a Curie temperature of 280 ° C. or higher.

For these reasons, the numerical ranges of claims 1 and 2 are limited.

As described above, the present invention has a high piezoelectric strain constant (d31), a low mechanical quality factor (Qm), little deterioration, a fine and uniform particle diameter, a strong grain boundary strength, and a Curie temperature. Thus, a piezoelectric ceramic composition having a high value can be obtained.

From the above, according to the present invention, it has a high piezoelectric strain constant, good durability against displacement at high temperatures, a uniform particle system, a high grain boundary strength, and a small cracking and chipping during processing. In addition, it is possible to form a laminated actuator having a thin interlayer and hardly causing a crack when driven.

[0044]

According to the present invention, the following effects can be obtained.

(1) The Curie temperature is sufficiently high and the piezoelectric strain constant (d31) in the longitudinal vibration mode is 200 × 1.
A piezoelectric ceramic exceeding 0 ^-12 m / v can be obtained, and there is no problem in use at a temperature of about 150 ° C., and an actuator with few cracks and chips during processing can be manufactured.

As a third component, lead zirconate titanate has P
By adding b (Co _1/3 Nb _2/3 ) O ₃ , deterioration when the constituted actuator is used at a high temperature (around 150 ° C.) can be reduced.

Further, W, Sb, Nb, Ta
At least one of them is WO_Three, Sb _TwoO_Three, Nb
_TwoO_Five, Ta_TwoO_FiveTo the weight of 1 mole of the main component
And 0.1 to 1.2% by weight of the piezoelectric strain constant
And the particle size after firing is smaller.
It is possible to do.

Further, as a sub-component, Si is converted to SiO ₂ and 0.01 to 0.1% by weight based on 1 mol of the main component.
By adding, the bonding force between the particles in the piezoelectric ceramic can be increased, and as a result, cracks and chips during processing can be reduced, and cracks during driving when an actuator is configured can be reduced. Becomes

(2) By substituting 0.01 to 0.06 mol of at least one of Sr and Ba for a part of Pb, it is possible to further increase the piezoelectric strain constant without deteriorating the aforementioned advantages. .

[Brief description of the drawings]

FIG. 1 shows three-point bending strength values when the value of Pb is plotted on the horizontal axis.

FIG. 11 is an electron micrograph showing the observation of the element particle size of Example 11 (Example).

FIG. 9 is an electron micrograph showing the particle size of an element of Comparative Example 9 (Comparative Example).

FIG. 15 is an electron micrograph showing a 15 (Example) element fracture surface.

FIG. 15 is an electron micrograph of a fractured surface of a device fabricated with the amount of SiO ₂ added being zero.

Claims (2)

[Claims] 1. The method of claim 1, wherein Pbx [(Co_1/3Nb_2/3) A Tib
 Zr1-ab] O_Three (However, 0.98 ≦ x ≦ 0.999, 0.01 ≦ a ≦
0.03, 0.43 ≦ b ≦ 0.49) as a main component, and at least one of W, Sb, Nb, and Ta as a subcomponent with respect to 1 mol of the main component.
Seeds WO_Three, Sb_TwoO _Three, Nb_TwoO_Five, Ta_TwoO_FiveConvert to
0.1 to 1.2% by weight, and Si as SiO_TwoConverted to 0.01
Characterized by containing 0.1 to 0.1% by weight.
Porcelain composition. 2. The method of claim 2, wherein Pbx [(Co_1/3Nb_2/3) A Tib
 Zr1-ab] O_Three (However, 0.98 ≦ x ≦ 0.999, 0.01 ≦ a ≦
0.03, 0.41 ≦ b ≦ 0.48) as main components, and P
b is at least one of Ba and Sr and is 0.01
To 0.06 mol, and at least one of W, Sb, Nb, and Ta as an accessory component with respect to the weight of 1 mole of the main component.
Seeds WO_Three, Sb_TwoO _Three, Nb_TwoO_Five, Ta_TwoO_FiveConvert to
0.1 to 1.2% by weight, and Si as SiO_TwoConverted to 0.01
Characterized by containing 0.1 to 0.1% by weight.
Porcelain composition.