JP2000169224A - Piezoelectric ceramic composition, piezoelectric device and piezoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition that has a large mechanical quality factor and shows small reduction in the mechanical quality factor by the high electric field driving and provide a small size and thin piezoelectric transducer. SOLUTION: The objective piezoelectric ceramic composition has the composition formula: (PbuA1-u)v (Sb1/2Nb1/2)xTiyZrz}2-vO3 where the elements corresponding to A in the formula is at least one selected from the group (A) consisting of La, Nd, Pr, Bi}, u, v, x, y and z in the formula satisfy the formulas and contains a manganese compound in an amount of 0.5-2 mol% calculated as MnO2.

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 suitable for, for example, an ultrasonic vibrator, an actuator, a piezoelectric transformer, and the like, and a piezoelectric device used for a power converter such as an inverter for a backlight of a liquid crystal display. It relates to a piezoelectric transformer.

[0002]

2. Description of the Related Art Piezoelectric materials are materials capable of converting electric energy into mechanical vibration energy or mechanical vibration energy into electric energy, such as ultrasonic vibrators, actuators, and piezoelectric transformers. Applications have been made. In these applications, piezoelectric materials with large electromechanical coupling and mechanical quality factors are used. As an example, Pb (Zn _1/3
Nb _2/3 ) O ₃ -Pb (Sn _1/3 Nb _2/3 ) O ₃ -PbTi
There is a composition obtained by adding MnO ₂ to an O ₃ —PbZrO ₃ composition, and it has been revealed that the composition exhibits excellent piezoelectricity (Japanese Patent Publication No. Sho 56-30714).

In recent years, higher output of piezoelectric devices has been demanded. On the other hand, with a high electric field drive or an increase in mechanical vibration, the piezoelectric material has a non-linear decrease in the mechanical quality factor and rapidly generates heat due to internal energy loss. Therefore, there is a need for a piezoelectric material in which the mechanical quality factor is not significantly reduced by high electric field driving.

[0004] Further, with the recent miniaturization of OA equipment, piezoelectric transformers have begun to spread to inverters for cold cathode tubes used as backlights for liquid crystal displays.
The piezoelectric transformer converts input electric energy into mechanical vibration energy and converts it into electric energy again, thereby increasing or decreasing the input voltage. Piezoelectric transformers used in such applications are required to have high conversion efficiency, and be small and thin.

A piezoelectric transformer is a device that utilizes the resonance of a piezoelectric element.
As the element length becomes shorter, the resonance frequency becomes higher. That is, downsizing leads to a higher driving frequency. However, when the driving frequency is increased, the conversion efficiency of the entire circuit including the piezoelectric transformer such as the inverter circuit is reduced due to the influence of the stray capacitance around the circuit, the frequency characteristics of the cold cathode tube, and the like. Therefore, there is a need for a piezoelectric transformer that is small and can be driven at a relatively low frequency.

[0006]

The above-mentioned conventional materials exhibit excellent piezoelectric properties when driven in a low electric field. However, the reduction in mechanical quality factor due to high electric field driving is large.

A first object of the present invention is to provide a piezoelectric ceramic composition having a large mechanical quality factor and a small decrease in the mechanical quality factor due to high electric field driving, and by using it as a piezoelectric material, An object of the present invention is to provide a piezoelectric device which generates a small amount of heat during high electric field driving and is capable of high output.

When a piezoelectric device having a laminated structure is formed, the step of bonding the electrode and the piezoelectric body can be omitted by simultaneously firing the silver palladium paste and the piezoelectric ceramic composition, and the piezoelectric device having the laminated structure can be easily manufactured. The effect that it can be manufactured in a good manner is obtained. The firing temperature when simultaneously firing the silver palladium paste and the piezoelectric ceramic composition is 1150
C is the upper limit, and it was difficult to adapt with conventional materials.

A second object of the invention is that it can be fired at a temperature below 1150 ° C., has a large mechanical quality factor,
Further, by providing a piezoelectric ceramic composition having a small decrease in mechanical quality factor due to high electric field driving, and a piezoelectric device capable of producing a high output with a small amount of heat generated during high electric field driving by using it as a piezoelectric body. is there.

[0010] When a constant electric energy is input to the piezoelectric transformer, the piezoelectric body is made thinner to increase (step down) the voltage.
Although the ratio increases, the conversion efficiency decreases.

A third object of the present invention is to provide a high conversion efficiency,
Another object of the present invention is to provide a thin piezoelectric transformer.

Furthermore, when a constant electric energy is input to the piezoelectric transformer, if the driving frequency of the piezoelectric transformer is reduced, the amplitude of the mechanical vibration increases, and the conversion efficiency decreases.

A fourth object of the present invention is to provide a small-sized piezoelectric transformer having high conversion efficiency even at a low driving frequency.

[0014]

Means for Solving the Problems The first invention (claim 1)
(Corresponding to the present invention described in), the composition formula is (Pb_uA_1-u) _v
｛(Sb_1/2Nb_1/2)_xTi_yZr_z｝_2-vO_ThreeAnd expressed
Where the symbol A consists of {La, Nd, Pr, Bi}
At least one component selected from (A), and u,
Piezoelectric ceramic composition where v, x, y, z are in the range shown by the following formula
MnO_Two0.5 to 2 mol% of Mn compound in terms of
Add

[0015]

X + y + z = 1 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized by the following formula:

According to the first aspect of the present invention, it is possible to provide a piezoelectric ceramic composition having a large mechanical quality factor and a small decrease in the mechanical quality factor due to high electric field driving.

The second of the present invention (corresponding to the invention of claim 2) is a composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb
_{1/2) x Ti y Zr z}} 2-v O 3] t - when expressed as (YMnO _{3) 1-t,} the symbol A is selected from {La, Nd, Pr, the group consisting of Bi} (A) At least one component, and t, u, v, x, y, z are within the range shown by the following formula

[0018]

(2) x + y + z = 1 0.970 ≦ t ≦ 0.995 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 It is.

According to the second aspect of the present invention, it is possible to provide a piezoelectric ceramic composition having a large mechanical quality factor and a small decrease in the mechanical quality factor due to high electric field driving.

The third invention (the invention according to claim 3)
(Correspondence) is the composition formula (Pb_uA_1-u) _v｛(Sb_1/2Nb
_1/2)_xTi_yZr_z｝_2-vO_ThreeWhen the symbol A is ｛L
a, Nd, Pr, Bi}.
At least a kind of component, and u, v, x, y, z
MnO with respect to the piezoelectric ceramic composition in the range shown by_Two
Add 0.5 to 2 mol% of Mn compound in terms of

[0021]

X + y + z = 1 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized in that:

According to a third aspect of the present invention, there is provided a piezoelectric ceramic composition which can be fired at a temperature lower than 1150 ° C., has a large mechanical quality factor, and has a small decrease in the mechanical quality factor due to high electric field driving. be able to.

The fourth of the present invention (corresponding to the invention of claim 4), the composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb
_{1/2) x Ti y Zr z}} 2-v O 3] t - when expressed as (YMnO _{3) 1-t,} the symbol A is selected from {La, Nd, Pr, the group consisting of Bi} (A) At least one component, and t, u, v, x, y, and z are in a range represented by the following equation.

[0024]

X + y + z = 1 0.970 ≦ t ≦ 0.995 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 It is.

According to a fourth aspect of the present invention, there is provided a piezoelectric ceramic composition which can be fired at a temperature lower than 1150 ° C., has a large mechanical quality factor, and has a small decrease in the mechanical quality factor due to high electric field driving. be able to.

A fifth aspect of the present invention (corresponding to the fifth aspect of the present invention) is a piezoelectric device characterized in that the piezoelectric ceramic composition of the first or second aspect of the present invention is used as a piezoelectric body.

According to the fifth aspect of the present invention, it is possible to provide a piezoelectric device which generates a small amount of heat when driven by a high electric field and is capable of high output.

A sixth aspect of the present invention (corresponding to the sixth aspect of the present invention) is a piezoelectric transformer, which is the piezoelectric device of the fifth aspect of the present invention.

According to the sixth aspect of the present invention, it is possible to provide a thin piezoelectric transformer having high conversion efficiency.

A seventh aspect of the present invention (corresponding to the seventh aspect of the present invention) is a piezoelectric transformer according to the sixth aspect of the present invention, comprising a lengthwise polarization section and a thickness direction polarization section. .

According to the seventh aspect of the present invention, a thin piezoelectric transformer having high conversion efficiency can be provided.

An eighth aspect of the present invention (corresponding to the eighth aspect of the present invention) is the piezoelectric transformer according to the seventh aspect of the present invention, which is excited in a half wavelength mode.

According to the eighth aspect of the present invention, it is possible to provide a small-sized piezoelectric transformer having high conversion efficiency even when the driving frequency is low.

A ninth aspect of the present invention (corresponding to the ninth aspect of the present invention) is a piezoelectric device comprising the piezoelectric ceramic composition of the third or fourth aspect and a silver-palladium paste electrode. is there.

According to the ninth aspect of the present invention, it is possible to provide a piezoelectric device which generates a small amount of heat when driven by a high electric field and is capable of high output.

A tenth aspect of the present invention (corresponding to the tenth aspect of the present invention) is a piezoelectric transformer, which is the ninth aspect of the present invention.

According to the tenth aspect of the present invention, the conversion efficiency is high,
In addition, a thin piezoelectric transformer can be provided.

An eleventh aspect of the present invention (corresponding to the eleventh aspect of the present invention) is the ninth aspect of the piezoelectric transformer according to the ninth aspect of the present invention, wherein the piezoelectric transformer includes a longitudinally polarized portion and a thickness polarized portion. .

According to the eleventh invention, the conversion efficiency is high,
In addition, a thin piezoelectric transformer can be provided.

A twelfth aspect of the present invention (corresponding to the twelfth aspect of the present invention) is the piezoelectric transformer according to the ninth aspect of the present invention, wherein the piezoelectric transformer is excited in a half wavelength mode.

According to the twelfth aspect of the present invention, it is possible to provide a small-sized piezoelectric transformer having high conversion efficiency even when the driving frequency is low.

The ninth to twelfth piezoelectric devices and piezoelectric transformers of the present invention are characterized in that they can be easily laminated by simultaneously firing a silver palladium paste and a piezoelectric ceramic composition.

[0043]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, the first embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. FIG. 1 is a perspective view showing the appearance of the piezoelectric transformer according to the first embodiment of the present invention. The arrow in FIG. 1 indicates the direction of the polarization axis of the piezoelectric body. The piezoelectric body driving section 1 in which the input electrodes 3a and b are formed on the main plane has been subjected to polarization processing in the thickness direction, and the piezoelectric body power generation section 2 in which the output electrode 4 is formed on the end upper surface is provided. , And between the input electrodes 3 a and b and the output electrode 4 are subjected to polarization processing in the length direction.

The operation of the piezoelectric transformer according to the present embodiment will be described. When an AC electric signal is applied between the input electrodes 3a and 3b, a mechanical vibration due to the inverse piezoelectric effect is excited in the piezoelectric body driving unit 1.

A voltage is generated between the output electrode 4 and the input electrode (common electrode) 3 due to the piezoelectric effect caused by the mechanical vibration.
It is extracted as an electric signal. As described above, the input voltage is converted into the output voltage. The relationship between the input voltage and the output voltage is determined by the dimensions of the piezoelectric body, the frequency of the applied AC electric signal, and the like. In this type of piezoelectric transformer, voltage conversion is most efficiently performed in one-wavelength mode (λ mode) of longitudinal extension vibration of the piezoelectric body (piezoelectric drive unit 1 + piezoelectric power generation unit 2). . Input electrode 3
The a and b and the output electrode 4 are formed, for example, by baking silver.

The piezoelectric driving unit 1 and the piezoelectric power generating unit 2
Composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb 1/2) x Ti y
An element represented by Zr _z ｝ _2-v O ₃ and corresponding to the symbol A in the composition formula is a group consisting of {La, Nd, Pr, Bi}.
(A) is at least one component selected from the above formula, u, v, x, y, z satisfy the following formula, and converted to MnO2 0.5 to 2 mol% Is a piezoelectric ceramic composition to which a Mn compound is added.

[0048]

X + y + z = 1 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 The piezoelectric ceramic composition according to the present embodiment satisfies the above conditions. It has been confirmed that, by satisfying the above, a large mechanical quality factor is obtained, and that a decrease in the mechanical quality factor due to high electric field driving is small. The details will be described in Examples described later.

Further, it has been confirmed that the piezoelectric transformer in the present embodiment can realize a high conversion efficiency and a low profile by using the piezoelectric ceramic composition, and details thereof will be described later in Examples. explain.

[0050] As a modification of this embodiment, in place of the piezoelectric ceramic composition in this embodiment, the composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb 1/2 ) _X Ti _y Zr _z ｝
_2- vO ₃ ] _t- (YMnO ₃ ) _{1 -t} , and the element corresponding to the symbol A in the composition formula is {La, Nd, Pr, B
At least one component selected from the group (A) consisting of i｝, and u, v, x, y, z in the above composition formula may be a piezoelectric ceramic composition that satisfies the following formula. Good.

[0051]

X + y + z = 1 0.970 ≦ t ≦ 0.995 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 It has been confirmed that the same effects as those of the piezoelectric ceramic composition and the piezoelectric transformer according to the embodiment can be obtained, and the details thereof will be described in Examples described later. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. This embodiment is the same as the piezoelectric transformer in the first embodiment described above, except for the piezoelectric ceramic composition of the present invention. Therefore, in the present embodiment, components that are not particularly described are assumed to be the same as those in the first embodiment, and the components having the same names as those in the first embodiment will be the same as those in the first embodiment unless otherwise described. It has the same function as the embodiment.

The configuration of the piezoelectric transformer according to the present embodiment is the same as that of FIG. The input electrodes 3a and 3b and the output electrode 4 are formed, for example, by baking silver or by baking a silver-palladium paste.

The piezoelectric body driving unit 1 and the piezoelectric body power generation unit 2
Composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb 1/2) x Ti y
An element represented by Zr _z ｝ _2-v O ₃ and corresponding to the symbol A in the composition formula is a group consisting of {La, Nd, Pr, Bi}.
(A) is at least one component selected from the above formula, u, v, x, y, z satisfy the following formula, and converted to MnO ₂ 0.5 to 2 mol % Of a Mn compound.

[0054]

X + y + z = 1 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 The piezoelectric ceramic composition according to the present embodiment satisfies the above conditions. By satisfying, it has been confirmed that it can be fired at a temperature of less than 1150 ° C., has a large mechanical quality factor, and has a small decrease in the mechanical quality factor due to high electric field driving. The details will be described later. An example will be described.

Further, it has been confirmed that the piezoelectric transformer in the present embodiment can realize a high conversion efficiency and a low profile by using the piezoelectric ceramic composition, and the details thereof will be described later in Examples. explain.

Further, when the piezoelectric transformer according to the present embodiment is manufactured, since the piezoelectric ceramic composition can be fired at a temperature of less than 1150 ° C., it can be fired simultaneously with the silver-palladium paste as an electrode to have a laminated structure. Therefore, a piezoelectric device having a laminated structure can be easily manufactured.

[0057] As a modification of this embodiment, in place of the piezoelectric ceramic composition in this embodiment, the composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb 1/2 ) _X Ti _y Zr _z ｝
_2- vO ₃ ] _t- (YMnO ₃ ) _{1 -t} , and the element corresponding to the symbol A in the composition formula is {La, Nd, Pr, B
At least one component selected from the group (A) consisting of i｝, and u, v, x, y, z in the above composition formula may be a piezoelectric ceramic composition that satisfies the following formula. Good.

[0058]

X + y + z = 1 0.970 ≦ t ≦ 0.995 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 Also in this modified example, It has been confirmed that the same effects as those of the piezoelectric ceramic composition and the piezoelectric transformer according to the embodiment can be obtained, and the details thereof will be described in Examples described later. (Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a perspective view showing the appearance of a piezoelectric transformer according to a third embodiment of the present invention. The arrow in FIG. 2 indicates the direction of the polarization axis of the piezoelectric body. Input electrode 8
The piezoelectric driving unit 5 in which a and b are formed on the main plane has been subjected to polarization processing in the thickness direction, and the piezoelectric power generating units 6 and 7 have long sides on both sides of the piezoelectric driving unit 5. And the output electrodes 9a, b, 9
c and d are formed.

The operation of the piezoelectric transformer according to the present embodiment will be described. When an AC electric signal is applied between the input electrodes 8a and 8b, a mechanical vibration due to the inverse piezoelectric effect is excited in the piezoelectric body driving unit 5. Due to the piezoelectric effect due to the mechanical vibration, a voltage is generated between the output electrodes 9a and b and the input electrodes 8a and 8b and between the output electrodes 9c and d and the input electrodes 8a and 8b.
It is extracted as an electric signal.

As described above, the input voltage is converted into the output voltage. The relationship between the input voltage and the output voltage is determined by the dimensions of the piezoelectric body, the frequency of the applied AC electric signal, and the like. In this type of piezoelectric transformer, the most efficient vibration in the half-wavelength mode (λ / 2 mode) of the longitudinal extension vibration of the piezoelectric body (piezoelectric drive unit 5 + piezoelectric body power generation units 6, 7) is obtained. Voltage conversion is performed. The vibration frequency of the half wavelength mode is 1 / the of the vibration frequency of the one wavelength mode.
2.

The input electrodes 8a, b and the output electrodes 9a,
b, c, and d are formed by, for example, silver printing.

The piezoelectric driving section 5 and the piezoelectric power generating sections 6 and 7
The composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb 1/2) x T
The _element represented by i _y Zr _z ｝ _2-v O ₃ and corresponding to the symbol A in the composition formula is a group consisting of {La, Nd, Pr, Bi}
(A) is at least one component selected from the above formula, u, v, x, y, z satisfy the following formula, and converted to MnO ₂ 0.5 to 2 mol % Of a Mn compound.

[0064]

X + y + z = 1 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 The piezoelectric ceramic composition according to the present embodiment satisfies the above conditions. It has been confirmed that, by satisfying the above, a large mechanical quality factor is obtained, and that a decrease in the mechanical quality factor due to high electric field driving is small. The details will be described in Examples described later. In addition, it has been confirmed that the piezoelectric transformer according to the present embodiment can achieve a high conversion efficiency and a low profile even when the driving frequency is low by using the piezoelectric ceramic composition, and details thereof will be described later. An example will be described.

Although the λ / 2 mode piezoelectric transformer in this embodiment has a center drive type configuration as shown in FIG. 2, the structure is not particularly limited, and the configuration shown in FIG. A similar effect can be obtained in a configuration having a length direction polarization portion and a thickness direction polarization portion and capable of exciting in the λ / 2 mode.

[0066] As a modification of this embodiment, in place of the piezoelectric ceramic composition in this embodiment, the composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb 1/2 ) _X Ti _y Zr _z ｝
_2- vO ₃ ] _t- (YMnO ₃ ) _{1 -t} , and the element corresponding to the symbol A in the composition formula is {La, Nd, Pr, B
At least one component selected from the group (A) consisting of i｝, and u, v, x, y, z in the above composition formula may be a piezoelectric ceramic composition that satisfies the following formula. Good.

[0067]

X + y + z = 1 0.970 ≦ t ≦ 0.995 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 It has been confirmed that the same effects as those of the piezoelectric ceramic composition and the piezoelectric transformer according to the embodiment can be obtained, and the details thereof will be described in Examples described later. (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the drawings. This embodiment is the same as the piezoelectric transformer in the third embodiment described above, except for the piezoelectric ceramic composition of the present invention. Therefore, in the present embodiment, components that are not particularly described are the same as those in the third embodiment, and components having the same names as those in the third embodiment are the same as those in the third embodiment unless otherwise specified. It has the same function as the embodiment.
Regarding the configuration of the piezoelectric transformer in the present embodiment,
It is the same as FIG.

The input electrodes 8a, b and the output electrodes 9a,
b, c, and d are, for example, those formed by baking silver or those formed by baking a silver palladium paste.

The piezoelectric driving section 5 and the piezoelectric power generating sections 6 and 7
The composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb 1/2) x T
The _element represented by i _y Zr _z ｝ _2-v O ₃ and corresponding to the symbol A in the composition formula is a group consisting of {La, Nd, Pr, Bi}
(A) is at least one component selected from the above formula, u, v, x, y, z satisfy the following formula, and converted to MnO ₂ 0.5 to 2 mol % Of a Mn compound.

[0070]

X + y + z = 1 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 The piezoelectric ceramic composition according to the present embodiment satisfies the above conditions. By satisfying, it has been confirmed that it can be fired at a temperature of less than 1150 ° C., has a large mechanical quality factor, and has a small decrease in the mechanical quality factor due to high electric field driving. The details will be described later. An example will be described.

Further, it has been confirmed that the piezoelectric transformer in the present embodiment can achieve a high conversion efficiency and a low profile even when the driving frequency is low by using the piezoelectric ceramic composition. Will be described in an embodiment described later.

The λ / 2 mode piezoelectric transformer in the present embodiment has a center drive type configuration as shown in FIG. 2, but the structure is not particularly limited, and the configuration shown in FIG. A similar effect can be obtained in a configuration having a length direction polarization portion and a thickness direction polarization portion and capable of exciting in the λ / 2 mode.

Further, when the piezoelectric transformer according to the present embodiment is manufactured, since the piezoelectric ceramic composition can be fired at a temperature lower than 1150 ° C., it is fired simultaneously with the silver-palladium paste to be an electrode to obtain a laminated structure. Therefore, a piezoelectric device having a laminated structure can be easily manufactured.

[0074] As a modification of this embodiment, in place of the piezoelectric ceramic composition in this embodiment, the composition formula _{[(Pb u A 1-u} ) v {(Sb 1/2 Nb 1/2 ) _X Ti _y Zr _z ｝
_2- vO ₃ ] _t- (YMnO ₃ ) _{1 -t} , and the element corresponding to the symbol A in the composition formula is {La, Nd, Pr, B
At least one component selected from the group (A) consisting of i｝, and u, v, x, y, z in the above composition formula may be a piezoelectric ceramic composition that satisfies the following formula. Good.

[0075]

X + y + z = 1 0.970 ≦ t ≦ 0.995 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 It has been confirmed that the same effects as those of the piezoelectric ceramic composition and the piezoelectric transformer according to the embodiment can be obtained, and the details thereof will be described in Examples described later.

Although the piezoelectric transformer using the piezoelectric ceramic composition of the present invention has been described in the first to fourth embodiments, the piezoelectric ceramic composition of the present invention is applied to a piezoelectric transformer. The present invention is not limited thereto, and can be applied to many piezoelectric devices including an ultrasonic vibrator and an actuator. By applying the piezoelectric ceramic composition of the present invention, a thin and small piezoelectric device and a laminated piezoelectric device that can be easily manufactured can be realized.

[0077]

Embodiments of the present invention will be described below.

The following examples correspond to the above-described first to fourth embodiments and their modifications, and correspond to the piezoelectric ceramic composition and the piezoelectric transformer, respectively.
The results of verification of the above-described effects by producing samples of those comparative examples are shown. (Example 1) Hereinafter, examples of piezoelectric ceramic compositions in the first and second embodiments (the same as the piezoelectric ceramic compositions in the third and fourth embodiments) and comparative examples thereof will be described. .

The starting materials for preparing the samples include chemical
High purity PbO, La_TwoO_Three, Nd _TwoO_Three, Pr_TwoO_Three, B
i_TwoO_Three, Sb_TwoO_Three, Nb_TwoO_Five, TiO_Two, ZrO_Two, Mn
CO _Three, Y_TwoO_ThreeSo that they have the specified composition.
Weigh and wet with a ball mill using zirconia balls.
Formula mixed. Where MnCO_ThreeIs MnO_TwoMust be converted to
I got the required amount. In addition, as a starting material,
Oxides, hydroxides, carbonates, alkoxides of each component element
Any of these may be used. Remove the mixture from the ball mill
After taking out and drying, 850 to 1100 ° C in air
For 2 hours. The calcined powder is converted by the ball mill described above.
Wet pulverization, take out the pulverized slurry from the ball mill
After drying, add polyvinyl alcohol solution
Granulated. Using the resulting granulated powder with a mold and press
Into a disk having a diameter of 20 mm and a thickness of about 2 mm. Molding
Hold the body in air at 700 ° C for 1 hour and bind
After the dark out, 1000 to 12 in air
It was baked while being kept at 60 ° C. for 2 hours. The fired body has a diameter of about 16
After processing into a disk about 1 mm thick, silver
Bake the electrodes, and in an insulating oil at 100 ° C, 1 to 5 kV / m
A DC electric field of m was applied to perform polarization processing. The resulting circle
Resonance and anti-resonance using a plate sample impedance analyzer
From the measurement by the method, the mechanical quality factor Q of the disk radial vibration
m was determined. Here, when the applied voltage is 0.1 Vrms
Calculate the Qm value and the Qm value when the applied voltage is 5 Vrms.
The degree of Qm reduction by electric field driving was evaluated.

Table 1 shows the composition, the firing temperature, the Qm value when the applied voltage is 0.1 Vrms, and the Qm value when the applied voltage is 5 Vrms. In addition, it was written to the right of the sample number.
(*) Indicates a sample outside the scope of the present invention.

[0081]

[Table 1] As is clear from the results shown in Table 1, the samples (samples other than sample numbers 1, 5, 10, 13, 14, 17, 18, and 22) corresponding to the piezoelectric ceramic composition according to the first embodiment of the present invention are shown. ) Shows a high mechanical quality factor Qm of 1400 or more at the time of low electric field driving (0.1 Vrms), and
Vrms) also shows a high Qm value of 1100 or more.

Further, samples corresponding to the piezoelectric ceramic composition according to the second embodiment of the present invention (sample numbers 15, 20,
21, 23, 25, 26, and 27)
A high Qm value was exhibited at a sintering temperature of less than 50 ° C., and it was confirmed that sintering can be performed simultaneously with the silver palladium paste.

On the other hand, the sample of the comparative example (sample No. 1,
5,10,13,14,17,18,22)
It can be seen that the Qm value is significantly reduced during high electric field driving.

(Example 2) Hereinafter, the piezoelectric ceramic compositions in the modified examples of the first and second embodiments (the piezoelectric ceramic compositions in the modified examples of the third and fourth embodiments are also the same) Examples) and comparative examples will be described.

The granulated powder obtained in the same manner as in Example 1 was weighed using a mold and a press to a diameter of 20 mm and a thickness of about 2 m.
m disk. The molded body is placed in air at 700
C. for 1 hour to perform binder-out, and then calcined in air at 1000-1260.degree. C. for 2 hours. After processing the fired body into a disc having a diameter of about 16 mm and a thickness of about 1 mm, silver electrodes are baked on both main surfaces thereof, and a DC electric field of 1 to 5 kV / mm is applied in an insulating oil at 100 ° C. to perform a polarization treatment. gave. From the measurement of the obtained disk sample by the resonance anti-resonance method using the impedance analyzer, the mechanical quality factor Qm of the disk radial vibration was determined. Here, the Qm value when the applied voltage was 0.1 Vrms and the Qm value when the applied voltage was 5 Vrms were obtained, and the degree of Qm reduction by high electric field driving was evaluated.

Table 2 shows the composition, the sintering temperature, the Qm value when the applied voltage is 0.1 Vrms, and the Qm value when the applied voltage is 5 Vrms. Note that (*) written to the right of the sample number indicates that the sample is outside the scope of the present invention.

[0087]

[Table 2] As is clear from the results shown in Table 2, the samples (sample numbers 28, 32, 37, 40, 41, 44, 4) corresponding to the piezoelectric ceramic composition in the modified example of the first embodiment of the present invention.
Samples other than 5, 49) show a high mechanical quality factor Qm of 1600 or more during low electric field driving (0.1 Vrms), and show a high Qm value of 1300 or more even at high electric field driving (5 Vrms). I have.

A sample corresponding to the piezoelectric ceramic composition according to the modification of the second embodiment of the present invention (sample No. 4)
2, 47, 48, 50, 52, 53, 54)
Furthermore, it shows a high Qm value at a firing temperature of less than 1150 ° C.,
It was confirmed that it was possible to fire simultaneously with the silver palladium paste.

On the other hand, the sample of the comparative example (sample No. 2)
8, 32, 37, 40, 41, 44, 45, and 49) show that the Qm value is remarkably reduced during high electric field driving.

(Example 3) An example of the piezoelectric transformer in the first and second embodiments and a comparative example thereof will be described below with reference to FIG. The granulated powder obtained in the same manner as in Example 1 was formed into a rectangular plate having a length of 50 mm, a width of 10 mm, and a thickness of about 3 mm using a mold and a press. After holding the molded body in air at 700 ° C. for 1 hour to perform binder-out,
It baked by holding at 0-1260 degreeC for 2 hours. The fired body was processed into a rectangular plate having a length of 40 mm, a width of 7 mm, a thickness of 2 mm and 1 mm. In the piezoelectric body driving unit 1, the input electrodes 3a and 3b were formed on the main plane by baking silver palladium paste, and were subjected to a polarization process in the thickness direction. The piezoelectric power generation unit 2 has a width of 1 mm.
Are formed, and the input electrodes 3a, b and the output electrode 4
Polarization treatment was performed in the length direction between them. The lengths of the piezoelectric driving unit 1 and the piezoelectric power generating unit 2 were each 20 mm. A load resistance of 120 kΩ was connected to the output electrode 4, and an AC electric signal was applied to the input electrodes 3a and 3b to excite mechanical vibration. The evaluation of the efficiency was performed for one wavelength mode (λ mode) of the longitudinal elongation vibration. Note that the input power Win is 4 W and the resonance frequency is about 80 kHz.

Table 3 shows the composition, the thickness of the piezoelectric element, and the efficiency of the piezoelectric transformer. In addition, it was written to the right of the sample number.
(*) Indicates that the sample is a comparative example.

[0092]

[Table 3] As is clear from the results shown in Table 3, samples corresponding to the piezoelectric transformer according to the first embodiment of the present invention (samples other than sample numbers 55, 56, 59, 60, 69, and 70).
Shows a high efficiency of 90% or more even when the piezoelectric element thickness is as thin as 1 mm.

The samples corresponding to the piezoelectric transformer according to the second embodiment of the present invention (samples Nos. 71 to 82) exhibited high efficiency at a firing temperature of less than 1150 ° C. It is possible to form a laminated structure by firing. Actually, when a laminated piezoelectric transformer composed of five layers of piezoelectric bodies (sample composition of sample No. 78) and six layers of silver-palladium electrodes was fabricated and the transformer characteristics were evaluated, it showed a high conversion efficiency and a high step-up ratio. It was confirmed that.

On the other hand, the sample of the comparative example (sample No. 5
5, 56, 59, 60, 69, and 70), the efficiency is significantly reduced particularly when the thickness of the piezoelectric element is as thin as 1 mm.

When the temperature rise after continuous driving of the piezoelectric transformers of Sample Nos. 56 and 58 for 40 min. Was evaluated, they were 38 ° C. and 15 ° C. with respect to the room temperature of 25 ° C., respectively. It was confirmed that the piezoelectric device using the piezoelectric ceramic composition according to the embodiment of the present invention generates a small amount of heat when driven by a high electric field and is capable of high output.

(Example 4) Hereinafter, an example of a piezoelectric transformer according to a modification of the first and second embodiments and a comparative example thereof will be described with reference to FIG.

[0097] The granulated powder obtained in the same manner as in Example 1 was weighed using a mold and a press to a length of 50 mm and a width of 10 mm.
It was formed into a rectangular plate having a thickness of about 3 mm. After the molded body was held in air at 700 ° C. for 1 hour to perform binder-out, it was held in air at 1000 to 1260 ° C. for 2 hours and fired. The fired body was processed into a rectangular plate having a length of 40 mm, a width of 7 mm, a thickness of 2 mm and 1 mm. Piezoelectric body driving unit 1
The input electrodes 3a and 3b were formed by baking silver palladium paste on the main plane, and were subjected to polarization processing in the thickness direction. The piezoelectric power generation section 2 formed an output electrode 4 having a width of 1 mm, and performed a polarization process between the input electrodes 3a and 3b and the output electrode 4 in the length direction. The lengths of the piezoelectric driving unit 1 and the piezoelectric power generating unit 2 were each 20 mm. 1 for output electrode 4
A load resistance of 20 kΩ was connected, and an AC electric signal was applied to the input electrodes 3a and 3b to excite mechanical vibration. The evaluation of the efficiency was performed for one wavelength mode (λ mode) of the longitudinal elongation vibration. Note that the input power Win is 4 W and the resonance frequency is about 80 kHz.

Table 4 shows the composition, the thickness of the piezoelectric element, and the efficiency of the piezoelectric transformer. In addition, it was written to the right of the sample number.
(*) Indicates that the sample is a comparative example.

[0099]

[Table 4] As is clear from the results shown in Table 4, the samples (samples other than sample numbers 83, 84, 87, 88, 97, and 98) corresponding to the piezoelectric transformer in the modified example of the first embodiment of the present invention were: Even when the piezoelectric element thickness is as thin as 1 mm, 91
%.

A sample corresponding to the piezoelectric transformer according to the modification of the second embodiment of the present invention (sample numbers 99 to 99)
110 sample) shows high efficiency at a firing temperature of less than 1150 ° C., and can be fired simultaneously with the silver-palladium paste to form a laminated structure. Actually, a laminated piezoelectric transformer composed of five layers of piezoelectric material (composition of the sample of sample No. 104) and six layers of silver-palladium electrodes was fabricated, and the transformer characteristics were evaluated. It was confirmed that.

On the other hand, the sample of the comparative example (sample No. 8)
3, 84, 87, 88, 97, and 98), the efficiency is significantly reduced particularly when the thickness of the piezoelectric element is as thin as 1 mm.

When the temperature rise of the piezoelectric transformers of Sample Nos. 84 and 86 after 40 min. Continuous driving was evaluated, the temperature rise was 36 ° C. and 12 ° C. with respect to the room temperature of 25 ° C., respectively. It was confirmed that the piezoelectric device using the piezoelectric ceramic composition according to the modification of the first embodiment generates a small amount of heat when driven by a high electric field and can output high power.

(Example 5) Examples of the piezoelectric transformer according to the third and fourth embodiments and comparative examples will be described below with reference to FIG.

The granulated powder obtained in the same manner as in Example 1 was weighed using a mold and a press to a length of 50 mm and a width of 10 mm.
It was formed into a rectangular plate having a thickness of about 3 mm. After the molded body was held in air at 700 ° C. for 1 hour to perform binder-out, it was held in air at 1000 to 1260 ° C. for 2 hours and fired. The fired body was processed into a rectangular plate having a length of 40 mm, a width of 7 mm, and a thickness of 1 mm. In the piezoelectric body driving unit 5, the input electrodes 8a and 8b were formed on the main plane by baking silver, and polarization processing was performed in the thickness direction. The piezoelectric power generating units 6 and 7 form output electrodes 9a, b, c, and d having a width of 1 mm, and as shown by arrows in FIG. 2, the input electrodes 8a, b and the output electrodes 9a, 9a, 9b.
Polarization was performed in the length direction between b and the output electrodes 9c and 9d. The arrow in FIG. 2 indicates the direction of the polarization axis. The length of the piezoelectric body driving section 5 is 20 mm, and the length of the piezoelectric body power generation section 6 is 6 mm.
And 7 each had a length of 10 mm. Four lead wires were connected to a load resistance of 120 kΩ, and each lead wire was connected to the output electrodes 9a, b, c, and d. An AC electric signal was applied to the input electrodes 8a and 8b to excite mechanical vibration. The evaluation of the efficiency was performed for a half-wavelength mode (λ / 2 mode) of the longitudinal vibration. The input power Win is 4 W, and the resonance frequency is about 40 kHz.

Table 5 shows the composition and the efficiency of the half-wave mode piezoelectric transformer. In addition, it was written to the right of the sample number.
(*) Indicates that the sample is a comparative example.

[0106]

[Table 5] The resonance frequency of the longitudinal stretching vibration differs depending on the vibration mode. When the resonance frequency is 40 kHz, the length of the piezoelectric element in one wavelength mode (λ mode) is about 80 mm, whereas the element length in the half wavelength mode (λ / 2 mode) is about 40 mm. It is. That is, in order to realize a small-sized piezoelectric transformer, it is effective to set the vibration mode to the half wavelength mode. However, when the resonance frequency decreases, the vibration amplitude increases and the mechanical distortion increases, so that the efficiency of the piezoelectric transformer decreases.

However, as is clear from the results shown in Table 5, the samples corresponding to the piezoelectric transformer according to the third embodiment of the present invention (sample numbers 111, 113, 118)
Other samples) show a high efficiency of 86% or more even when the driving frequency is as low as 40 kHz.

Further, a sample corresponding to the piezoelectric transformer according to the fourth embodiment of the present invention (sample numbers 119 to 124)
Sample) further shows high efficiency at a firing temperature of less than 1150 ° C., and can be fired simultaneously with the silver palladium paste to form a laminated structure. Actually, a stacked half-wave mode piezoelectric transformer composed of five layers of piezoelectric material (composition of the sample of sample No. 122) and six layers of silver-palladium electrodes was fabricated, and the transformer characteristics were evaluated. It was confirmed that a high boost ratio was exhibited.

On the other hand, the sample of the comparative example (sample No. 11)
1, 113 and 118) show that the efficiency is significantly reduced.

(Example 6) Hereinafter, examples of piezoelectric transformers according to modifications of the third and fourth embodiments and comparative examples will be described with reference to FIG.

The granulated powder obtained in the same manner as in the case of Example 1 was weighed using a mold and a press to a length of 50 mm and a width of 10 mm.
It was formed into a rectangular plate having a thickness of about 3 mm. After the molded body was held in air at 700 ° C. for 1 hour to perform binder-out, it was held in air at 1000 to 1260 ° C. for 2 hours and fired. The fired body was processed into a rectangular plate having a length of 40 mm, a width of 7 mm, and a thickness of 1 mm. In the piezoelectric body driving unit 5, the input electrodes 8a and 8b were formed on the main plane by baking silver, and polarization processing was performed in the thickness direction. The piezoelectric power generating units 6 and 7 form output electrodes 9a, b, c, and d having a width of 1 mm, and as shown by arrows in FIG.
Polarization was performed in the length direction between b and the output electrodes 9c and 9d. The arrow in FIG. 2 indicates the direction of the polarization axis. The length of the piezoelectric body driving section 5 is 20 mm, and the length of the piezoelectric body power generation section 6 is 6 mm.
And 7 each had a length of 10 mm. Four lead wires were connected to a load resistance of 120 kΩ, and each lead wire was connected to the output electrodes 9a, b, c, and d. An AC electric signal was applied to the input electrodes 8a and 8b to excite mechanical vibration. The evaluation of the efficiency was performed for a half-wavelength mode (λ / 2 mode) of the longitudinal vibration. Note that the input power Win is 4 W and the resonance frequency is about 40 kHz.

Table 6 shows the composition and the efficiency of the half-wave mode piezoelectric transformer. In addition, it was written to the right of the sample number.
(*) Indicates that the sample is a comparative example.

[0113]

[Table 6] As is clear from the results shown in Table 6, the samples (samples other than the sample numbers 125, 127, and 132) corresponding to the piezoelectric transformer in the modified example of the third embodiment of the present invention have a low drive frequency of 40 kHz. Sometimes it shows a high efficiency of 87% or more.

Further, a sample (sample number 133) corresponding to the piezoelectric transformer in the modification of the fourth embodiment of the present invention.
138) show high efficiency at a firing temperature of less than 1150 ° C., and can be fired simultaneously with the silver-palladium paste to form a laminated structure. Actually, a stacked half-wave mode piezoelectric transformer composed of five layers of piezoelectric material (composition of the sample of sample No. 134) and six layers of silver-palladium electrodes was manufactured, and the transformer characteristics were evaluated. It was confirmed that a high boost ratio was exhibited.

On the other hand, the sample of the comparative example (sample No. 12)
5, 127, 132) shows that the efficiency is significantly reduced.

As described above, it was confirmed that the first to fourth embodiments described above were effective.

Although the λ / 2 mode piezoelectric transformer in the third and fourth embodiments has a center drive type configuration as shown in FIG. 2, the structure is not particularly limited. A similar effect can be expected in a configuration such as the configuration shown in FIG. 1, which has a lengthwise polarization portion and a thickness direction polarization portion and can be excited in the λ / 2 mode.

[0118]

As is apparent from the above description, the present invention according to claims 1 and 2 has a piezoelectric ceramic composition having a large mechanical quality factor and a small decrease in the mechanical quality factor due to high electric field driving. Things can be provided.

The present invention according to claims 3 and 4 is a piezoelectric ceramic composition which can be fired at a temperature lower than 1150 ° C., has a large mechanical quality factor, and has a small decrease in the mechanical quality factor due to high electric field driving. Can be provided.

According to the fifth and ninth aspects of the present invention, it is possible to provide a piezoelectric device which generates a small amount of heat when driven by a high electric field and is capable of high output.

The present invention according to claims 6, 7, 10, and 11 can provide a thin piezoelectric transformer having high conversion efficiency.

According to the eighth and twelfth aspects of the present invention, it is possible to provide a small-sized piezoelectric transformer having high conversion efficiency even at a low driving frequency.

The piezoelectric device and the piezoelectric transformer according to the ninth to twelfth aspects of the present invention have an advantage that they can be easily laminated by simultaneously firing a silver palladium paste and a piezoelectric ceramic composition.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an appearance of a piezoelectric transformer according to first and second embodiments of the present invention.

FIG. 2 is a perspective view illustrating an appearance of a piezoelectric transformer according to third and fourth embodiments of the present invention.

[Explanation of symbols]

 1, 5 Piezoelectric drive unit 2, 6, 7 Piezoelectric power generation unit 3, 8 Input electrode 4, 9 Output electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Nakatsuka 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masamitsu Nishida 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co. 72) Inventor Hiroyuki Hase 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 4G031 AA07 AA09 AA11 AA12 AA14 AA19 AA32 AA34 AA35 BA10

Claims (12)

[Claims] The method according to claim 1] composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb
_{1/2) x Ti y Zr z}} 2- v when expressed as O _3, symbol A is {L
a, Nd, Pr, Bi} at least one component selected from the group (A), and u, v, x, y, z are within the range represented by the following formula. On the other hand, MnO ₂
0.5 to 2 mol% of a Mn compound is added, expressed as: x + y + z = 1 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized by the following: 2. The composition formula is [(Pb_uA_1-u)_v｛(Sb_1/2N
b_1/2)_xTi_yZr_z｝ _2-vO_Three]_t-(YMnO_Three)_1-tWhen
When expressed, the symbol A changes from {La, Nd, Pr, Bi}
At least one component selected from the group (A),
And t, u, v, x, y, and z are within the range represented by the following formula: x + y + z = 1 0.970 ≦ t ≦ 0.995 0.84 ≦ u ≦ 0.99 0.95 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.20 0.38 ≦ y ≦ 0.59 0.32 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized by the following: 3. A composition formula _{(Pb u A 1-u)} v {(Sb 1/2 Nb
_{1/2) x Ti y Zr z}} 2- v when expressed as O _3, symbol A is {L
a, Nd, Pr, Bi} at least one component selected from the group (A), and u, v, x, y, z are within the range represented by the following formula. On the other hand, MnO ₂
0.5 + 2 mol% of a Mn compound is added, expressed as follows: x + y + z = 1 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized by the following: 4. A composition formula of [(Pb_uA_1-u)_v｛(Sb_1/2N
b_1/2)_xTi_yZr_z｝ _2-vO_Three]_t-(YMnO_Three)_1-tWhen
When expressed, the symbol A changes from {La, Nd, Pr, Bi}
At least one component selected from the group (A),
And t, u, v, x, y, and z are within the range represented by the following equation: x + y + z = 1 0.970 ≦ t ≦ 0.995 0.92 ≦ u ≦ 0.99 0.99 ≦ v ≦ 1.05 0.01 ≦ x ≦ 0.08 0.45 ≦ y ≦ 0.59 0.37 ≦ z ≦ 0.50 A piezoelectric ceramic composition characterized by the following: 5. A piezoelectric device using the piezoelectric ceramic composition according to claim 1 as a piezoelectric body. 6. A piezoelectric transformer using the piezoelectric device according to claim 5. 7. The piezoelectric transformer according to claim 6, further comprising a lengthwise polarization part and a thickness direction polarization part. 8. The piezoelectric transformer according to claim 7, wherein excitation is performed in a half-wave mode. 9. A piezoelectric device comprising the piezoelectric ceramic composition according to claim 3 and a silver / palladium paste electrode. 10. A piezoelectric transformer using the piezoelectric device according to claim 9. 11. The piezoelectric transformer according to claim 10, further comprising a lengthwise polarization part and a thickness direction polarization part. 12. The piezoelectric transformer according to claim 11, wherein excitation is performed in a half wavelength mode.