JP2002316871A - Piezoelectric ceramics composition and piezoelectric element using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric ceramics composition which has high strength without undergoing deterioration in electric characteristics, and to provide a piezoelectric element which can sufficiently deal with high frequencies even when thinned. SOLUTION: The piezoelectric ceramics composition is obtained by allowing a composite oxide having a Perovskite structure as the main component and SiO2 as an assistant component to enter into a solid solution with earth other, and is provided with the compositional rations in the formula of Pba (Mn2d-1 Nbd Sb2-3d )x Zry Tiz } O3 +bSiO2 (wherein, (a) is 0.95 to 0.985; (x) is 0.04 to 0.18; (y) is 0.36 to 0.52; (d) is 0.55 to 0.65; and (b) is 0.01 to 0.05).

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 useful for a ferroelectric piezoelectric ceramic and a piezoelectric element using the same, and more particularly to a piezoelectric resonator, a piezoelectric actuator, a piezoelectric buzzer, and a piezoelectric element. The present invention relates to a piezoelectric element particularly useful for a filter, a piezoelectric oscillator, and the like, and a piezoelectric ceramic composition suitably used for the piezoelectric element.

[0002]

2. Description of the Related Art A piezoelectric element is an element having a function of converting electric vibration into mechanical vibration or a element having a function of converting mechanical vibration into electric vibration. Specific applications of the piezoelectric element include a piezoelectric vibrator, a piezoelectric resonator, a piezoelectric filter, and a piezoelectric oscillator. Traditionally,
Piezoelectric ceramics (piezoelectric ceramics, piezoelectric ceramics) are widely used as the material for the piezoelectric element. As this piezoelectric ceramic, a composite oxide having a perovskite structure represented by the general formula ABO ₃ is very suitably used.

For example, a composition for a piezoelectric ceramic having a perovskite structure has been proposed by the present applicant (JP-B-51-11798). This composition has Pb ｛(Mn, Nb, Sb) in a specific composition range.
It is a ternary ceramic composition of Zr, TiｒO ₃ system. In such a porcelain composition, since the mechanical quality factor Qm can be increased, elastic loss due to mechanical vibration can be reduced.

In recent years, in the technical field of the piezoelectric element, the thickness of the piezoelectric element itself has been reduced in order to cope with a higher frequency. When the thickness is reduced, sufficient mechanical strength is required so that the piezoelectric element is not broken even by high-frequency mechanical vibration. In general, a piezoelectric ceramic for a piezoelectric element requires a transverse rupture strength of at least 140 MPa or more even when it is made thin. Therefore, the demand for a high-strength material capable of withstanding high-frequency vibration during thinning is increasing as a piezoelectric ceramic composition.

Further, since the piezoelectric element is used for various purposes as described above, various characteristics are required for the piezoelectric ceramics, which are materials for the piezoelectric element, according to the purpose of use. For example, taking a piezoelectric filter as an example, this piezoelectric filter has a function of outputting only a signal in a specific frequency band from input signals having various frequency components. Therefore, the piezoelectric ceramic is required not only to have a high electromechanical coupling coefficient (K ₁₅ ) but also to have a flat frequency temperature coefficient as a temperature characteristic in order to ensure high reliability.

[0006]

However, in conventional piezoelectric ceramic compositions including the above composition, it is difficult to secure sufficient strength. If sufficient strength is not obtained, the piezoelectric element intermediate during processing or the piezoelectric element after processing will be easily destroyed if impact is applied,
Problems such as a reduction in the yield in manufacturing the piezoelectric element and a reduction in the reliability of the piezoelectric element itself will occur.

For example, when a piezoelectric element is manufactured with the above composition, the transverse rupture strength of the piezoelectric element is approximately in the range of about 110 to 130 MPa, and substantially only the strength of about 120 MPa can be realized. Therefore, it is difficult to manufacture a thinned piezoelectric element.

Further, in the piezoelectric element, not only the strength when the thickness is reduced, but also the characteristics according to the purpose of use must be ensured. In particular, the piezoelectric resonator, a piezoelectric vibrator, a piezoelectric filter, and a piezoelectric oscillator, as exemplified by the piezoelectric filter, the strength, the electrical characteristics such as temperature characteristic of high electromechanical coupling coefficient K ₁₅ and the resonance frequency Must also be realized.

However, as a material having a perovskite structure which is preferably used as a piezoelectric ceramic composition, a material which can realize both the above-mentioned strength and electric characteristics has not been known.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a piezoelectric material capable of realizing strength capable of withstanding high-frequency vibration even in a thinned state and exhibiting excellent electric characteristics. It is an object of the present invention to provide a porcelain composition, in particular, a piezoelectric porcelain composition capable of realizing a transverse rupture strength of 150 MPa or more, and a high-quality piezoelectric element obtained by using the composition and capable of sufficiently coping with high frequencies.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that a perovskite structure represented by the general formula ABO ₃ used as a main component of a piezoelectric ceramic composition is obtained. The composite oxide has the following formula:

[0012]

Embedded image

If the composition system shown in FIG. 1 further contains SiO ₂ as a subcomponent and the main component and subcomponent are in a solid solution with each other, the Pb content and the Si
The inventors have found that by setting the O ₂ amount in the optimum range, it is possible to improve both the strength and the piezoelectric characteristics of the obtained thinned piezoelectric element, and have completed the present invention.

That is, in order to solve the above-mentioned problems, the piezoelectric ceramic composition according to the present invention comprises a piezoelectric ceramic composition containing a composite oxide having a perovskite structure represented by the general formula ABO ₃ as a main component. In the above, SiO ₂ is further contained as a subcomponent, and these main components and subcomponents form a solid solution with each other.

[0015]

Embedded image

(Where a is 0.95 to 0.985)
, X is in the range of 0.04 to 0.18, y is in the range of 0.36 to 0.52, and z is 0.
44 to 0.52, and d is 0.55 to 0.6
5 and b is in the range of 0.01 to 0.05).

According to the above structure, the amount of the first element in the complex oxide of the main component represented by the general formula ABO ₃ is small, so that A in the structure of the complex oxide
(Hereinafter appropriately referred to as A site), the first element is surely arranged. Therefore, the unreacted first element component is prevented from being precipitated and present at the grain boundary of the composite oxide. As a result, in the obtained piezoelectric element,
Strength can be improved without lowering electrical characteristics.

Specifically, the perovskite structure is AO
The gap ₃ of the three-dimensional structure can be regarded as having entered is B. Therefore, in the case where the atom at the A site is viewed as the center in AO ₃ , it is merely a simple cubic lattice, and is easily distorted. Therefore, it is suitable as a material for a piezoelectric element, that is, a main component of a piezoelectric ceramic composition.

The composite compound having a perovskite structure can be obtained by using an oxide of the first element group and the second element group as a starting material, blending them, and firing them under predetermined conditions. The first element is P
b, and the second element group is Zr, Ti, M
n, Nb, and Sb.

Here, if the first element entering the A site does not completely react and precipitates at the grain boundary of the composite oxide in an unreacted state, the present inventors have found that the strength, particularly the transverse rupture strength, decreases. Was found independently. Therefore, the molar amount of the first element is set smaller than the total molar amount of the second element group in order to suppress the unreacted first element from being precipitated at the grain boundary. As described above, the mole fraction of the first element is in the range of 0.95 to 0.985 with respect to the total mole of the second element group.

Therefore, in the method for producing a piezoelectric ceramic composition according to the present invention, when the oxides of the first and second elements, which are the starting materials (raw materials) of the composite oxide, are prepared, The amount of each oxide is determined such that the molar amount of one element is smaller than the total molar amount of the second element group.

In the above composite oxide, the composition ratio of the stoichiometric composition is theoretically A: B = 1: 1, as apparent from the general formula ABO ₃ . Here, in the present invention, the molar amount of the first element is smaller than the total molar amount of the second element group.
The molar fraction of the first element with respect to the element group is less than 1, which is smaller than the stoichiometric molar fraction (hereinafter, stoichiometric).

Thus, the molar fraction of the first element is 0.9
In the range of 5 to 0.985, the composition of the first element is less than 1 which is smaller than the stoichiometric amount, so that the unreacted first element is further prevented from being precipitated at the grain boundary. . Therefore, the bending strength of the piezoelectric element can be set to 140 MPa or more, and a sufficient value of the electromechanical coupling coefficient K ₁₅ can be secured.

Specifically, the molar fraction of the first element is 0.9
If less than 5, since the amount of the first element enters the A site is too small, as shown in the results of the examples described below, is not preferable because the electro-mechanical coupling coefficient K ₁₅ of the piezoelectric element decreases. On the other hand, when it exceeds 0.985, the first unreacted
This is not preferable because elements are easily precipitated, and as shown in the results of Examples described later, the bending strength of the piezoelectric element is reduced.

In the present invention, among the above sub-elements (groups), the 2-1 element group, that is, the total mole fraction of Mn, Nb and Sb is in the range of 0.04 to 0.18. is necessary. Mn, Nb, be greater than 0.18 even when the total molar fraction is less than 0.04 of Sb, as shown in the results of the examples described below, the electromechanical coupling coefficient K ₁₅ of the piezoelectric element is reduced Is not preferred.

Further, M contained in the above 2-1 element group
As the composition ratio of n, Nb and Sb, it is necessary that a relationship of Mn: Nb: Sb = 2d-1: d: 2-3d (where 0.55 ≦ d ≦ 0.65) is satisfied.

[0027] d exceeds 0.55 or less than 0.65, as shown in the results of Examples appearing later, is not preferable because the electro-mechanical coupling coefficient K ₁₅ of the piezoelectric element decreases.

In the present invention, it is necessary that the mole fraction of the 2-2 element, that is, Zr, in the sub-elements (group) is in the range of 0.36 to 0.52.

[0029] be greater than 0.52 even when the molar fraction of Zr is less than 0.36, as shown in the results of the examples described below, since the electromechanical coupling coefficient K ₁₅ of the piezoelectric element decreases Not preferred.

It should be noted that, among the above sub-element groups, the blending amount of the 2-3 elements, ie, Ti, that is, the mole fraction,
It suffices that the total mole fraction, which is the sum of the mole fractions of the element group, is set to 1. Specifically, the mole fraction of the 2-1 element group is x, the mole fraction of the 2-2 element is y, the mole fraction of the 2-3 element is z, and the total mole fraction of the second element group is Assuming that the ratio is M, x + y + z = M = 1 0.04 (mol fraction) ≦ x ≦ 0.18 (mol fraction) 0.36 (mol fraction) ≦ y ≦ 0.52 (mol fraction) The relationship is established. Therefore, the maximum range in the molar fraction of Ti is in the range of 0.30 to 0.60 [0.30 (mol fraction) ≦ z ≦ 0.60 (mol fraction)]
Becomes

However, the molar fraction of Ti is as follows:
As shown in the results of the respective examples described later, 0.44 to 0.
52 [0.44 (molar fraction) ≦ z ≦ 0.52
(Molar fraction)].

Regardless of whether the molar fraction of Ti is less than 0.44 or more than 0.52, the electromechanical coupling coefficient K _{15 of the} piezoelectric element
Decrease. If the mole fraction of each sub-element (group) included in the second element group is within the above range, it is possible to obtain a piezoelectric element having excellent physical properties. Therefore, the electromechanical coupling coefficient K ₁₅ not only the flexural strength of the piezoelectric element is improved.

[0033] In contrast, the mole fraction of each sub-element (s), Outside the above range, since the electromechanical coupling coefficient K ₁₅ of the piezoelectric element decreases, required in the case of using a piezoelectric element as a piezoelectric filter Is not preferable because the characteristics of

In the piezoelectric ceramic composition according to the present invention, the content of the Si compound is 0.1% in terms of SiO ₂ with respect to 100% by weight of the composite oxide as the main component.
It is necessary to be within the range of 01% by weight to 0.05% by weight. If the content of the Si compound is within the above range, it is possible to realize a bending strength of the piezoelectric element of 150 MPa or more, so that it is possible to obtain a high-strength piezoelectric element having stable various electric characteristics. .

On the other hand, when the content of the Si compound is 0.
If the content is less than 01% by weight, the bending strength of the piezoelectric element will be less than 150 MPa as shown in the results of the examples described later, and the significance of adding the Si compound as a subcomponent will be reduced.
On the other hand, if it exceeds 0.05% by weight, the sintering temperature for forming the piezoelectric element becomes too high. Therefore, especially the first
When Pb is used as an element, Pb tends to evaporate during firing, and the composition of Pb in the composite oxide changes from a design value. Therefore electromechanical coupling coefficient K ₁₅ of the piezoelectric element is reduced, other properties is not preferable because it becomes difficult to control.

Further, in the piezoelectric ceramic composition according to the present invention, Al ₂ O ₃ may be contained as an auxiliary component. That is, the piezoelectric ceramic composition according to the present invention preferably contains the above-described composite oxide as a main component, contains SiO ₂ as a sub-component, and forms a two-component solid solution in which these are dissolved together. Further, Al ₂
It may be a ternary solid solution containing O ₃ .

The content of Al ₂ O ₃ may be within a range that does not affect the properties of the piezoelectric ceramic composition. Al
_As an example of the content of ₂ O ₃ , for example,
The content is in the range of 0.08% by weight, but is not particularly limited thereto. However, when the content of Al ₂ O ₃ is excessive, the characteristics of the piezoelectric ceramic composition may be affected, such as a decrease in the electromechanical coupling coefficient K _15, which is not preferable.

As described above, the piezoelectric ceramic composition according to the present invention contains a composite oxide having a perovskite structure as a main component and SiO ₂ as a subcomponent, and the main component and the subcomponent form a solid solution with each other. And the following equation

[0039]

Embedded image

Is a solid solution represented by However,
The following relationships are established for a, b, x, y, z, and d.

0.95 (mol fraction) ≤ a ≤ 0.985 (mol fraction) 0.01 (wt%) ≤ b ≤ 0.05 (wt%) 0.04 (mol fraction) ≤ x ≤ 0.18 (mol fraction) 0.36 (mol fraction) ≤ y ≤ 0.52 (mol fraction) 0.44 (mol fraction) ≤ z ≤ 0.52 (mol fraction) 0.55 ≤ d ≦ 0.65 In other words, in the present invention, when the content of the composite oxide as the main component is 100% by weight, SiO _{2 as the} subcomponent is
Is formed in the range of 0.01% by weight to 0.05% by weight.

Further, in the present invention, as described above, Al ₂ O ₃ may be contained as an auxiliary component. That is, in the piezoelectric ceramic composition of the present invention, Al ₂ O ₃ may be added as a sub-component within a range that does not impair the properties to form a ternary solid solution.

A piezoelectric element according to the present invention is characterized by using the above-described piezoelectric ceramic composition. Specifically, the piezoelectric element according to the present invention is obtained by obtaining the above piezoelectric ceramic composition by firing, polarizing it under predetermined conditions, and then forming a predetermined electrode pattern thereon. Can be. As shown in FIG. 2, one example of the piezoelectric element has a configuration in which an electrode pattern 2 is formed on a piezoelectric element main body 1. The piezoelectric element is polarized along the longitudinal direction of the piezoelectric element as indicated by an arrow in the drawing.

According to the above configuration, the transverse rupture strength can be increased to 150 MPa or more even when the thickness is reduced. Moreover,
With an electromechanical coupling coefficient K ₁₅ can be controlled within the range of 45% to 55%, can also be arbitrarily change the temperature coefficient of the resonant frequency. As a result, it can be particularly usefully used as a piezoelectric resonator, a piezoelectric actuator, a piezoelectric buzzer, a piezoelectric filter, a piezoelectric oscillator, and the like.

The above-mentioned electrode pattern is appropriately formed according to the use of the piezoelectric element, and is not limited to a specific electrode or pattern. The condition for polarization is not particularly limited, and a conventionally known method can be used.

[0046] Further, the electromechanical coupling coefficient K ₁₅ required for various piezoelectric elements also, because it varies depending on the application of the piezoelectric element, but is not particularly limited. The change in the temperature coefficient of the resonance frequency is also appropriately changed according to the application of the piezoelectric element, and is not particularly limited.

[0047]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Lead oxide (PbO)_Two), Oxidation
Tan (TiO)_Two), Zirconium oxide (ZrO)_Two), Charcoal
Manganese acid (MnCO_Three), Niobium oxide (Nb
_TwoO_Five), Antimony oxide (Sb_TwoO_Three), Silicon oxide
(SiO_Two), And aluminum oxide (Al_TwoO _Three)
And distributing them so that the final composition shown in Table 1 is obtained.
The combined powder was obtained. The above blended powder is ball milled
After 2-24 hours wet mixing, dehydration, drying,
Calcination was performed at 900 to 1000 ° C. for 2 hours.

After adding an appropriate amount of a binder to the compounded powder obtained after the calcination, the mixture was wet-mixed and pulverized again by a ball mill for 2 to 24 hours, and then dewatered to obtain a powder for press molding. After press-molding the powder for press-molding on a block, it is baked in the air at a temperature of 1150 to 1300 ° C. for 2 to 4 hours to obtain a 20 mm × 30 mm × 7 m
m, that is, a piezoelectric ceramic composition according to the present invention was obtained.

After the obtained fired body was polished to a thickness of 6.7 mm, an electrode pattern was formed on the sintered body. Further, the sintered body is immersed in oil in a range of 2.5 kV / mm to 3.5 kV.
Polarization was performed under the conditions of V / mm and 60 ° C to 100 ° C. The sintered body after polarization was aged at 150 ° C. to 240 ° C. for 1 hour, further cut into strips of 6.7 mm × 30 mm × 0.260 mm, and polished until the thickness became 0.210 mm. Electrode patterns were formed on both sides.

Thereafter, the sintered body was reduced to 6.7 mm × 1.6 mm.
The piezoelectric element (1) according to the present invention was obtained by cutting into a size of × 0.210 mm. For this piezoelectric element, the bending strength, the electrical characteristics of the thickness shear vibration mode using an impedance analyzer (electromechanical coupling coefficient K ₁₅ ), and the temperature change rate of the resonance frequency (within the range of −20 ° C. to 80 ° C.) are measured. did. Table 2 shows the measurement results.

Example 2 In the composite oxide, P
A piezoelectric element (2) was obtained in the same manner as in Example 1 except that the amount of lead oxide was changed so that the molar fraction of b became the final composition shown in Table 1. Various characteristics of this piezoelectric element were measured in the same manner as in Example 1. Table 2 shows the measurement results.

[Comparative Examples 1.2] In the above composite oxide, as shown in Table 1, except that the amount of lead oxide was changed so that the molar fraction of Pb was 0.945 or 0.99. In the same manner as in Example 1, comparative piezoelectric elements (1) and (2) were obtained. Various characteristics of these piezoelectric elements were measured in the same manner as in Example 1. Table 2 shows the measurement results.
Shown in

Comparative Example 3 The same as Example 1 except that the compounding amount of lead oxide in the composite oxide was changed so that the molar fraction of Pb was 1, as shown in Table 1. Thus, a comparative piezoelectric element (3) was obtained. Various characteristics of this piezoelectric element were measured in the same manner as in Example 1. Table 2 shows the measurement results.

[0055]

[Table 1]

[0056]

[Table 2]

As is clear from the results shown in Table 2, the comparative piezoelectric element (3) has a significantly lower flexural strength, but the piezoelectric elements (1) and (2) according to the present invention have at least a lower resistance. It can be seen that a high value can be realized for the folding strength.
Further, in the piezoelectric elements (1) and (2) according to the present invention, since the mole fraction of Pb as the first element is within the above-mentioned range, it is compared with the comparative piezoelectric elements (1) and (2). When not only the bending strength, it is seen that both excellent value in both of the temperature change rate of the electromechanical coupling coefficient K ₁₅ and the resonant frequency.

[Examples 3 to 7] In the composite oxide, titanium oxide (T) was prepared such that the mole fraction of each sub-element group included in the second element group had the final composition shown in Table 3.
Example 1 except that the amounts of iO ₂ ), zirconium oxide (ZrO ₂ ), manganese carbonate (MnCO ₃ ), niobium oxide (Nb ₂ O ₅ ), and antimony oxide (Sb ₂ O ₃ ) were changed. In the same manner as described above, the piezoelectric elements (3) to
(7) was obtained. For these piezoelectric elements, the first embodiment
Various characteristics were measured in the same manner as described above. Table 4 shows the measurement results.

[Comparative Examples 4 to 10] In the composite oxide, titanium oxide (T) was prepared such that the mole fraction of each sub-element group included in the second element group had the final composition shown in Table 3.
Example 1 except that the amounts of iO ₂ ), zirconium oxide (ZrO ₂ ), manganese carbonate (MnCO ₃ ), niobium oxide (Nb ₂ O ₅ ), and antimony oxide (Sb ₂ O ₃ ) were changed. In the same manner as described above, the comparative piezoelectric element (4)
~ (10) was obtained. Various characteristics of these comparative piezoelectric elements were measured in the same manner as in Example 1. Table 4 shows the measurement results.

[0060]

[Table 3]

[0061]

[Table 4]

As is clear from the results shown in Table 4, in the piezoelectric elements (3) to (7) according to the present invention, the mole fraction of each sub-element (group) included in the second element group falls within the above-described range. since it is, compared as compared with the piezoelectric element (4) to (10), as well as bending strength, it is seen that the electromechanical coupling coefficient K ₁₅ is also high value.

[Examples 8 and 9] In the above composite oxide, the value of d was changed as shown in Table 5 in order to change the final composition of Mn, Nb and Sb contained in the second element group. Except for the above, piezoelectric elements (8) and (9) were obtained in the same manner as in Example 1. About these piezoelectric elements,
Various characteristics were measured in the same manner as in Example 1. Table 6 shows the measurement results.

[Comparative Examples 11 and 12] In the above composite oxide, the value of d was changed as shown in Table 5 in order to change the final composition of Mn, Nb and Sb contained in the second element group. Comparative piezoelectric elements (11) and (12) were obtained in the same manner as in Example 1 except for the above. Various characteristics of these comparative piezoelectric elements were measured in the same manner as in Example 1.
Table 6 shows the measurement results.

[0065]

[Table 5]

[0066]

[Table 6]

As is evident from the results in Table 6, in the piezoelectric elements (8) and (9) according to the present invention, the mole fraction of each sub-element (group) included in the second element group falls within the range described above. since it is, compared as compared with the piezoelectric element (11), (12), as well as bending strength, it is seen that the electromechanical coupling coefficient K ₁₅ is also high value.

[Examples 10 to 12] In the above-mentioned composite oxide, the blending of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as auxiliary components was made so as to have the contents shown in Table 7. Piezoelectric elements (10) to (10) according to the present invention in the same manner as in Example 1 except that the amount was changed.
(12) was obtained. For these piezoelectric elements, the first embodiment
Various characteristics were measured in the same manner as described above. Table 8 shows the measurement results.

[Comparative Examples 13 to 18] In the above-mentioned composite oxide, blending of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as sub-components so as to have the contents shown in Table 7 Comparative piezoelectric elements (13) to (18) were obtained in the same manner as in Example 1 except that the amount was changed. Various characteristics of these piezoelectric elements were measured in the same manner as in Example 1. Table 8 shows the measurement results.

[0070]

[Table 7]

[0071]

[Table 8]

As is clear from Table 8, in the piezoelectric elements (10) to (12) according to the present invention, since the content of the auxiliary component is within the above-mentioned range, the comparative piezoelectric elements (13) to (18) It can be seen that not only the transverse rupture strength but also the electromechanical coupling coefficient K ₁₅ show a higher value than that of.

[0073]

As described above, the piezoelectric ceramic composition according to the present invention contains a composite oxide having a perovskite structure as a main component and SiO ₂ as a subcomponent, and the main component and the subcomponent are mixed with each other. Form a solid solution with each other,

[0074]

Embedded image

(Where a is 0.95 to 0.985)
, X is in the range of 0.04 to 0.18, y is in the range of 0.36 to 0.52, and d is 0.
B is in the range of 55 to 0.65, and b is 0.01 to 0.0
5 is within the range of 5).

Further, a piezoelectric element according to the present invention has a configuration using the above piezoelectric ceramic composition. Therefore, the bending strength can be increased to 150 MPa or more even when the thickness is reduced, and the electromechanical coupling coefficient K ₁₅ is 45% to 55%.
And the temperature coefficient of the resonance frequency can be arbitrarily changed.

As a result, the above configuration has an effect that it can be particularly usefully used as a piezoelectric resonator, a piezoelectric actuator, a piezoelectric buzzer, a piezoelectric filter, a piezoelectric oscillator, and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a perovskite structure of a composite oxide contained as a main component in a piezoelectric ceramic composition according to the present invention.

FIG. 2 is a schematic perspective view showing an example of a piezoelectric element according to the present invention.

[Explanation of symbols]

 1 piezoelectric element body 2 electrode pattern

Continued on the front page (72) Inventor Hitoshi Takagi 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (reference) 4G031 AA11 AA12 AA14 AA19 AA30 AA32 AA34 BA10 CA01

Claims (2)

[Claims] 1. A piezoelectric ceramic composition containing, as a main component, a composite oxide having a perovskite structure represented by the general formula ABO ₃ , wherein SiO ₂ is further contained as a subcomponent. The sub-components form a solid solution with each other and have the following formula: (However, a is in the range of 0.95 to 0.985, x is in the range of 0.04 to 0.18, and y is 0.
36 to 0.52, and d is 0.55 to 0.6
5, z is in the range of 0.44 to 0.52, and b is in the range of 0.01 to 0.05). Piezoelectric ceramic composition. 2. A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1.