JP3527208B2 - Piezoelectric ceramic composition and piezoelectric element using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric ceramic composition and a piezoelectric element using the same.

[0002]

2. Description of the Related Art Piezoelectric ceramic compositions used in piezoelectric ceramic elements such as piezoelectric ceramic resonators generally include lead zirconate titanate (PZT) or lead titanate (PT). Has been used.

In recent years, lead-free porcelain compositions have been developed as alternatives to these porcelain compositions. Specifically, a piezoelectric ceramic composition containing a bismuth layer compound as a main component has been attracting attention as a ceramic for a sensor / actuator that can be used even at high temperatures.

[0004]

However, the piezoelectric ceramic composition containing a bismuth layered compound as a main component, which has been reported in the past, has a problem that the electromechanical coupling coefficient is not sufficiently large and has not been put to practical use. .

In order to solve the above problems, it is an object of the present invention to provide a piezoelectric ceramic composition having a larger electromechanical coupling coefficient than conventional bismuth layered compounds, and a piezoelectric element using the same.

[0006]

To achieve the above object, the first piezoelectric ceramic composition of the present invention has a composition of the formula: Ca
M _X Bi _4-X Ti _4-X (Nb _1-A Ta _A ) _X O ₁₅ (however, M
Is at least one element selected from Ca, Sr and Ba, and 0.0 <A ≦ 1.0, 0.0 <X ≦ 0.
The material represented by 6) contains the main component. In other words, the first piezoelectric ceramic composition consists of the main component only, or the main component and the subcomponent. According to the first piezoelectric ceramic composition, a piezoelectric ceramic composition which has a larger electromechanical coupling coefficient than the conventional bismuth layered compound and does not contain lead can be obtained.

The composition of the first piezoelectric ceramic composition is represented by the formula: C
aM _X Bi _4-X Ti _4-X (Nb _1-A Ta _A ) X O ₁₅ (however,
M is at least one selected from Ca, Sr and Ba
Elements of 0.0 <A ≦ 1.0, 0.0 <X ≦ 0.
6) as a main component and MnO as a subcomponent
_It may further include ₂ . According to the above constitution, a piezoelectric ceramic composition having excellent characteristics such as mechanical quality factor can be obtained.

The first piezoelectric ceramic composition is the above MnO ₂
May be less than or equal to 0.6% by mass. According to the above configuration, it is possible to prevent polarization from becoming difficult.

The second porcelain composition of the present invention has the composition: CaM _Y Bi _4-Y Ti _4-Y (Nb _1-B Ta _B ) _Y O
₁₅ (provided that M is at least one element selected from Ca, Sr and Ba, and 0.0 ≦ B ≦ 1.0, 0.
0 <Y ≤0.6) as a main component,
Contains WO ₃ as an accessory component. According to the second piezoelectric ceramic composition, a piezoelectric ceramic composition having a larger electromechanical coupling coefficient than the conventional bismuth layered compound and containing no lead can be obtained.

In the second piezoelectric ceramic composition, the WO
The content of ₃ may be 0.5% by mass or less. According to the above configuration, it is possible to prevent polarization from becoming difficult.

The second piezoelectric ceramic composition may further contain MnO ₂ as an accessory component. According to the above constitution, a piezoelectric ceramic composition having excellent characteristics such as mechanical quality factor can be obtained.

The first piezoelectric element of the present invention is a piezoelectric element having a piezoelectric body made of a piezoelectric ceramic composition, and the piezoelectric ceramic composition has a composition of the formula: CaM _X Bi _4-X Ti.
_4-X (Nb _1-A Ta _A ) _X O ₁₅ (wherein M is at least one element selected from Ca, Sr and Ba,
0.0 <A ≦ 1.0, 0.0 < X ≦ 0.6) is contained as a main component. According to the first piezoelectric element, it is possible to obtain a piezoelectric element which does not contain lead and has good electric characteristics.

[0013] In the first piezoelectric element, the piezoelectric ceramic composition, the composition has the _{formula: CaM X Bi 4-X Ti} 4-X (Nb 1-A T
a _A ) _X O ₁₅ (However, M is selected from Ca, Sr and Ba.
At least one element, and 0.0 ≦ A ≦ 1.
0, 0.0 <X ≦ 0.6) as the main component
And it may further comprise MnO ₂ as an auxiliary component. The second piezoelectric element of the present invention is a piezoelectric element comprising a piezoelectric body made of a piezoelectric ceramic composition, the piezoelectric ceramic composition, the composition has the _{formula: CaM Y Bi 4-Y Ti} 4-Y ( Nb _1-B Ta
_B ) _Y O ₁₅ (where M is at least one element selected from Ca, Sr and Ba, and 0.0 ≦ B ≦ 1.
0, 0.0 <Y ≦ 0.6) is contained as a main component, and WO ₃ is contained as a subcomponent.
According to the second piezoelectric element, it is possible to obtain a piezoelectric element which does not contain lead and has good electric characteristics.

In the first piezoelectric element, the MnO ₂ content in the piezoelectric ceramic composition may be 0.6% by mass or less.

The first piezoelectric element further includes two vibrating electrodes formed on the piezoelectric body so as to face each other with the piezoelectric body sandwiched therebetween, and the thickness t of the piezoelectric body and the area of the vibrating electrode are provided. S and S may satisfy the relationship of 22 ≦ S / t ² . According to the above configuration, a piezoelectric resonator that is easy to design and manufacture can be obtained.

In the first piezoelectric element, the vibrating electrode may be circular.

The second piezoelectric element of the present invention is a piezoelectric element having a piezoelectric body made of a piezoelectric ceramic composition, and the piezoelectric ceramic composition has a composition of the formula: CaM _Y Bi _4-Y Ti.
_4-Y (Nb _1-B Ta _B ) _Y O ₁₅ (wherein M is at least one element selected from Ca, Sr and Ba,
0.0 ≦ B ≦ 1.0, 0.0 ≦ Y ≦ 0.6) as a main component and WO ₃ as a sub-component. According to the second piezoelectric element, it is possible to obtain a piezoelectric element which does not contain lead and has good electric characteristics.

In the second piezoelectric element, the content of WO ₃ in the piezoelectric ceramic composition may be 0.5% by mass or less.

In the second piezoelectric element, the piezoelectric ceramic composition may further contain MnO ₂ as an accessory component.

The second piezoelectric element further includes two vibrating electrodes formed on the piezoelectric body so as to face each other with the piezoelectric body interposed therebetween, and the thickness t of the piezoelectric body and the area of the vibrating electrode are provided. S and S may satisfy the relationship of 22 ≦ S / t ² .

In the second piezoelectric element, the vibrating electrode may be circular.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In Embodiment 1, a first piezoelectric ceramic composition of the present invention will be described.

The piezoelectric ceramic composition of Embodiment 1 (hereinafter sometimes referred to as piezoelectric ceramic composition 1) has a composition of the formula: CaM.
_X Bi _4-X Ti _4-X (Nb _1-A Ta _A ) _X O ₁₅ (where M is at least one element selected from Ca, Sr and Ba, and 0.0 ≦ A ≦ 1.0, 0.0 <X ≦ 0.6)
Contains the material represented by. Where A is 0
It is more preferable to satisfy ≦ A ≦ 0.4. Also, X
More preferably satisfies 0.1 ≦ X ≦ 0.4.

The material serving as the main component is, for example, CaCO.
₃, SrCO₃, BaCO₃, Bi₂O ₃, TiO₂, Nb₂
O_Five, And Ta₂O_FiveA compound such as
It can be formed by mixing.

The piezoelectric ceramic composition 1 may further contain MnO ₂ or the like as an accessory component. The content rate of MnO ₂ is
It is preferably 0.6% by mass or less, more preferably 0.01% by mass to 0.6% by mass,
It is particularly preferable to be in the range of 0.2% by mass to 0.5% by mass.

The piezoelectric ceramic composition 1 may be formed only from the main component. When the piezoelectric ceramic composition 1 is composed of only the main component, the composition of the piezoelectric ceramic composition 1 can be represented by the following formula. _{CaM X Bi 4-X Ti 4} -X (Nb 1-A Ta A) X O 15 may also be formed from the major and secondary components. In this case, the piezoelectric ceramic composition 1 contains the main component in a content rate of 96 mass% or more. When the piezoelectric ceramic composition 1 contains a main component and a subcomponent, the piezoelectric ceramic composition 1 can be formed by mixing and firing the starting materials constituting both. The composition of the piezoelectric ceramic composition 1 containing MnO ₂ as an accessory component can be represented by the following formula. _{[CaM X Bi 4-X Ti} 4-X (Nb 1-A Ta A) X O 15]
_100-L (MnO ₂ ) _L Here, L represents the content ratio (mol%) of MnO ₂ ,
It is a value greater than 0.

The piezoelectric ceramic composition 1 has a triple harmonic thickness.
Frequency constant N for longitudinal vibration_3tBe as large as possible
Is preferred. For example, N_3tIs 7300Hz ・ m or more
Preferably there is. In this case, the radial
Spread mode frequency constant N _pIs 2500 Hz / m or more
It gets bigger and bigger.

According to the piezoelectric ceramic composition 1 of Embodiment 1,
A piezoelectric ceramic composition containing no lead and having a larger electromechanical coupling coefficient than conventional bismuth layered compounds can be obtained.

(Embodiment 2) In Embodiment 2, a second piezoelectric ceramic composition of the present invention will be described.

The piezoelectric ceramic composition of Embodiment 2 (hereinafter sometimes referred to as piezoelectric ceramic composition 2) has a composition of the formula: CaM.
_Y Bi _4-Y Ti _4-Y (Nb _1-B Ta _B ) _Y O ₁₅ (where M is at least one element selected from Ca, Sr and Ba, and 0.0 ≦ B ≦ 1.0, 0.0 ≦ Y ≦ 0.6)
The material represented by the formula (1) is contained as a main component, and WO ₃ is contained as an auxiliary component. Here, it is more preferable that B satisfies 0 ≦ B ≦ 0.4. It is more preferable that Y satisfies 0.1 ≦ Y ≦ 0.4.

The piezoelectric ceramic composition 2 contains 96% by mass of the main component.
Included at the above content rates. The main material is, for example,
CaCO ₃ , SrCO ₃ , BaCO ₃ , Bi ₂ O ₃ , Ti
It can be formed by mixing compounds such as O ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ in a predetermined ratio.

The content of WO ₃ as an accessory component is preferably 0.5% by mass or less, and 0.01% by mass to 0.
It is more preferably within the range of 5% by mass, and particularly preferably within the range of 0.1% by mass to 0.4% by mass.

The piezoelectric ceramic composition 2 contains Mn in addition to WO _3.
O ₂ and the like may also contain as a secondary component. The content of MnO ₂ is preferably 0.6% by mass or less,
It is more preferably in the range of mass% to 0.6 mass%, and particularly preferably in the range of 0.2 mass% to 0.5 mass%.

The piezoelectric porcelain composition 2 can be formed by mixing the starting materials constituting the main component and the subcomponents and firing them. The composition of the piezoelectric ceramic composition 2 containing WO ₃ and MnO ₂ as subcomponents can be represented by the following formula. _{[CaM Y Bi 4-Y Ti} 4-Y (Nb 1-B Ta B) Y O 15]
_100-LN (MnO ₂ ) _L (WO ₃ ) _N where L and N are MnO ₂ and WO ₃ , respectively.
Content (mol%) of 0 ≦ L and 0 <N.

The piezoelectric ceramic composition 2 has a triple harmonic thickness.
Frequency constant N for longitudinal vibration_3tBe as large as possible
Is preferred. For example, N_3tIs 7300Hz ・ m or more
Preferably there is. In this case, the radial
Spread mode frequency constant N _pIs 2500 Hz / m or more
It gets bigger and bigger.

According to the piezoelectric ceramic composition 2 of Embodiment 2,
A piezoelectric ceramic composition containing no lead and having a larger electromechanical coupling coefficient than conventional bismuth layered compounds can be obtained.

(Embodiment 3) In Embodiment 3, a first piezoelectric element of the present invention will be described.

The piezoelectric element of the third embodiment (hereinafter, piezoelectric element 1
In some cases), the piezoelectric body composed of the piezoelectric ceramic composition 1 described in the first embodiment is provided.

The piezoelectric element 1 is specifically, for example, a piezoelectric resonator such as a ceramic oscillator or a filter, a piezoelectric vibrating body such as a buzzer or a sounder, or a displacement element such as an actuator.

As an example of the piezoelectric element 1, a piezoelectric resonator 10
1 is a perspective view of FIG. Referring to FIG. 1, a piezoelectric resonator 1
0 includes a piezoelectric body 11 and electrodes 12a and 12b formed on the two main surfaces of the piezoelectric body 11. Electrode 12a
And 12b have leads 12c and 12 respectively.
d is connected.

The electrodes 12a and 12b have a circular shape. However, the shape is not limited to a circle, and may be another shape such as a square or a rectangle. The electrodes 12a and 12b are formed in the same shape so as to face each other with the piezoelectric body 11 interposed therebetween.

Area S of electrode 12a (electrode 12b) and piezoelectric
The thickness t of the body 11 is 22 ≦ S / t ²Meet the relationship of
And are preferred. In other words, the electrode 12a (the electrode 12
The diameter D in b) and the thickness t of the piezoelectric body 11 are 5.3 ≦ D /
It is preferable to satisfy the relationship of t.

Since the piezoelectric element 1 of the third embodiment uses the piezoelectric ceramic composition 1 of the first embodiment, it does not contain lead and has good electrical characteristics.

(Embodiment 4) In Embodiment 4, a second piezoelectric element of the present invention will be described.

The piezoelectric element of the fourth embodiment (hereinafter referred to as piezoelectric element 2
However, since only the material of the piezoelectric element 1 of the third embodiment is different from the material of the piezoelectric body, duplicate description will be omitted.
The piezoelectric body of the piezoelectric element 2 is the piezoelectric ceramic composition 2 of the second embodiment.
Consists of.

Since the piezoelectric element 2 of the fourth embodiment uses the piezoelectric ceramic composition 2 of the second embodiment, it does not contain lead and has good electrical characteristics.

[0048]

EXAMPLES The present invention will be described in more detail with reference to examples.

(Example 1) In Example 1, an example of producing the piezoelectric ceramic compositions 1 and 2 of Embodiments 1 and 2 will be described.

In Example 1, CaCO ₃ , SrCO ₃ , B
aCO ₃ , WO ₃ , Mn ₃ O ₄ , Bi ₂ O ₃ , TiO ₂ , Nb ₂
O _5, and Ta ₂ O ₅ as starting materials, to form a plurality of piezoelectric ceramic composition. Note that Mn ₃ O ₄ becomes MnO ₂ by the heat treatment during firing.

Specifically, the composition of the piezoelectric ceramic composition is shown in Table 1.
The starting materials were weighed so as to have the predetermined ratios shown in Table 3 to 3, and they were sufficiently mixed by a ball mill so as to be uniform. Next, the mixture of starting materials was calcined at 600 ° C. to 800 ° C. for 2 hours to form a compound. This compound was pulverized again with a ball mill, and polyvinyl alcohol was added thereto to granulate to obtain a powder of a piezoelectric ceramic composition.

This powder was uniaxially pressed at a pressure of 70 MPa to form a disk having a diameter of 13 mm. This disc was fired at 1100 ° C to 1200 ° C for 2 hours to form a disc-shaped sample. After polishing this sample to a thickness of 0.3 mm, electrodes made of Ag were formed on the upper surface and the lower surface of the sample, respectively. Then, this sample was subjected to 5 kV / mm
An electric field of 10 kV / mm was applied for 30 minutes to perform polarization treatment to obtain a disk made of piezoelectric ceramics (piezoelectric material).

With respect to the disk made of this piezoelectric ceramic, the capacitance C at 1 kHz, the disk thickness t, the disk diameter D, the resonance frequency Fr of the disk thickness direction vibration, and the disk thickness direction vibration Anti-resonance frequency Fa, resonance frequency fr of disk radial vibration, anti-resonance frequency f of disk radial vibration
a, Poisson's ratio σ ^E , and resonance resistance R were measured. Then, from these values, the relative permittivity ε _r , the electromechanical coupling coefficient k _p in the radial direction spreading mode of the disk, the electromechanical coupling coefficient k _t in the thickness longitudinal vibration mode, the mechanical quality coefficient Q _M , and the radial direction The frequency constant N _p of the spreading mode was calculated.

The calculation results are shown in Tables 1 to 3. In addition, Table 1
The composition of the main component of the formula is: Ca _{1 + T} Bi _4-T Ti _4-T (Nb _1-C
Ta _C ) _T O ₁₅ and the composition of the main component in Table 2 is represented by the formula: C
represented by _{aSr T Bi 4-T Ti 4} -T (Nb 1-C Ta C) T O 15, the composition of the main component in Table 3, wherein: CaBa _T Bi _4-T Ti
Represented by _{4-T (Nb 1-C} Ta C) T O 15. C and T in the main component column of Tables 1 to 3 indicate the values of C and T in the above formula. In the table, sample No. "*" Before "" indicates that it is a comparative example. It should be noted that the sample No of Table 1. Two
3 and 4 are reference examples.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

When the piezoelectric ceramic is used as the piezoelectric body of the piezoelectric element utilizing the thickness longitudinal vibration mode including triple harmonics, what is particularly important is the electromechanical coupling coefficient k _t of the thickness longitudinal vibration mode. . As is clear from Tables 1 to 3, the piezoelectric ceramic of Sample 1 (CaBi ₄ Ti ₄ O
_The electromechanical coupling coefficient kt of the piezoelectric ceramics of the present invention was larger than that of ₁₅ ). In this way, CaBi ₄ Ti ₄
The electromechanical coupling coefficient k _t could be increased by solid-dissolving Nb or Ta and the element M in O ₁₅ . Also,
By adding WO ₃ to CaBi ₄ Ti ₄ O ₁₅
The electromechanical coupling coefficient k _t could be increased.

In particular, the electromechanical coupling coefficient k _t and the mechanical quality coefficient Q _M can be increased by using the piezoelectric ceramic composition with C ≦ 0.0 and 0.1 ≦ T ≦ 0.2.

(Example 2) In Example 2, an example in which the piezoelectric resonator 10 is manufactured using the porcelain composition of the present invention will be described.

In the piezoelectric resonator of Example 2, the piezoelectric ceramic composition of sample 35 of Example 1 was used as the piezoelectric body. The piezoelectric body was formed by dicing and polishing a disk sample after polarization. Further, as the electrodes 12a and 12b, circular electrodes made of silver were used. The electrodes were formed by vapor deposition.

In the second embodiment, the size is 5.1 × 5.1 m.
A piezoelectric body having a thickness m and a thickness t of 0.29 mm was used. And
Three types of piezoelectric resonators were produced by changing the diameter D of the Ag electrode from about 1.2 mm to about 1.6 mm. The impedance characteristics of these three types of piezoelectric resonators are shown in FIG. In addition, FIG. 3 shows the results of similar impedance characteristics measured for a piezoelectric resonator using a conventional lead-based piezoelectric ceramic as a piezoelectric body. 2 and 3 also show the relationship between the area S of the electrode and the thickness t of the piezoelectric body.

As is apparent from FIG. 2, in the piezoelectric resonator of the present invention having a resonance frequency of about 25 MHz, D / t = 5.5.
Even in the case of (S / t ² = 29.7), there was no unnecessary vibration between the resonance frequency and the anti-resonance frequency. Further, in the piezoelectric resonator of the present invention, D / t = 4.1 (S / t ² = 1
7.5), D / t = 4.8 (S / t ² = 23.1), and D / t = 5.5 (S / t ² = 29.7), No sub-resonance appeared with the anti-resonance frequency.

On the other hand, in the piezoelectric resonator using the conventional piezoelectric ceramic composition containing lead, 5.3 ≦ D / t (2
In the case of 2 ≦ S / t ² ), the amplitude of the sub-resonance becomes large near the anti-resonance frequency, and the impedance waveform largely splits near the anti-resonance frequency. in this way,
In the piezoelectric resonator using the conventional piezoelectric ceramic composition, 5.3
When ≦ D / t, a practical piezoelectric resonator could not be manufactured.

As described above, the piezoelectric resonator using the piezoelectric ceramic composition of the present invention has few design restrictions. Further, since a large electrode can be used, even if the center of the vibrating electrodes on the two principal surfaces is deviated, the influence thereof is reduced, which is advantageous in manufacturing.

Although the embodiments of the present invention have been described above with reference to examples, the present invention is not limited to the above embodiments and can be applied to other embodiments based on the technical idea of the present invention. .

[0067]

As described above, according to the first and second piezoelectric ceramic compositions of the present invention, the electromechanical coupling coefficient is larger than that of the conventional bismuth layered compound, and the piezoelectric ceramic composition does not contain lead. The thing is obtained.

Further, according to the first and second piezoelectric elements of the present invention, it is possible to obtain a piezoelectric element containing no lead and having excellent electric characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a piezoelectric resonator of the present invention.

FIG. 2 is a diagram showing an example of impedance characteristics of the piezoelectric resonator of the present invention.

FIG. 3 is a diagram showing an example of impedance characteristics of a conventional piezoelectric resonator.

[Explanation of symbols]

10 Piezoelectric resonator (piezoelectric element) 11 Piezoelectric body 12a, 12b electrodes D diameter t thickness

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP 2001-192266 (JP, A) JP 2001-130956 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 35 / 00-35/22 C04B 35/42-35/51 REGISTRY (STN) CA (STN)

Claims (16)

(57) [Claims] 1. The composition has the formula: CaM _X Bi _4-X Ti _4-X (Nb
_1-A Ta _A ) _X O ₁₅ (where M is Ca, Sr and Ba)
At least one element selected from: 0.0 <A
A piezoelectric ceramic composition containing as a main component a material represented by ≦ 1.0, 0.0 <X ≦ 0.6). 2. The composition has the formula: CaM _x Bi _4-x Ti _4-x (Nb).
_1-A Ta _A ) X O ₁₅ (where M is Ca, Sr and Ba)
At least one element selected from 0.0 ≦ A
≦ 1.0, 0.0 <X ≦ 0.6)
Min and, pressure electromagnetic unit composition containing MnO ₂ as an auxiliary component. 3. The piezoelectric ceramic composition according to claim 2, wherein the content of MnO ₂ is 0.6% by mass or less. 4. The composition has the formula: CaM _Y Bi _4-Y Ti _4-Y (Nb
_1-B Ta _B ) _Y O ₁₅ (where M is Ca, Sr and Ba)
At least one element selected from 0.0 ≦ B
≦ 1.0, 0.0 <Y ≦ 0.6) as a main component, and a piezoelectric ceramic composition containing WO ₃ as an accessory component. 5. The piezoelectric ceramic composition according to claim 4, wherein the WO ₃ content is 0.5% by mass or less. 6. The piezoelectric ceramic composition according to claim 4, further comprising MnO ₂ as an accessory component. 7. A piezoelectric element comprising a piezoelectric body made of a piezoelectric ceramic composition, wherein the piezoelectric ceramic composition has a composition represented by the formula: CaM _X Bi _4-X Ti.
_4-X (Nb _1-A Ta _A ) _X O ₁₅ (wherein M is at least one element selected from Ca, Sr and Ba,
A piezoelectric element comprising a material represented by 0.0 <A ≦ 1.0, 0.0 < X ≦ 0.6) as a main component. 8. A pressure provided with a piezoelectric body made of a piezoelectric ceramic composition.
A conductive element, wherein the piezoelectric ceramic composition, the composition has the formula: CaM _X Bi _4-X Ti
_4-X (Nb _1-A Ta _A ) _X O ₁₅ (However, M is Ca, Sr or
And at least one element selected from Ba,
0.0 ≦ A ≦ 1.0, 0.0 <X ≦ 0.6)
The material as a main component, pressure-electronic device containing MnO ₂ as an auxiliary component. 9. The piezoelectric element according to claim 8, wherein the content of the MnO ₂ in the piezoelectric ceramic composition is 0.6% by mass or less. 10. A vibrating electrode formed on the piezoelectric body so as to face each other with the piezoelectric body sandwiched therebetween, wherein a thickness t of the piezoelectric body and an area S of the vibrating electrode are 22.
The piezoelectric element according to any one of claims 7 to 9, wherein the relationship of ≤ S / t2 is satisfied. 11. The piezoelectric element according to claim 10, wherein the vibrating electrode has a circular shape. 12. A piezoelectric element comprising a piezoelectric body made of a piezoelectric ceramic composition, the piezoelectric ceramic composition, the composition has the formula: CaM _Y Bi _4-Y Ti
_4-Y (Nb _1-B Ta _B ) _Y O ₁₅ (wherein M is at least one element selected from Ca, Sr and Ba,
0.0 ≦ B ≦ 1.0, 0.0 <Y ≦ 0.6) as a main component and WO ₃ as a sub-component. 13. The piezoelectric element according to claim 12, wherein the content of WO ₃ in the piezoelectric ceramic composition is 0.5% by mass or less. 14. The piezoelectric ceramic composition contains M as an accessory component.
The piezoelectric element according to claim 12, further comprising nO ₂ . 15. The apparatus further comprises two vibrating electrodes formed on the piezoelectric body so as to face each other with the piezoelectric body sandwiched therebetween, and a thickness t of the piezoelectric body and an area S of the vibrating electrode are 22.
The piezoelectric element according to any one of claims 12 to 14, which satisfies the relationship of ≤S / t2. 16. The piezoelectric element according to claim 15, wherein the vibrating electrode has a circular shape.