JP2003034574A - Piezoelectric ceramic composition and piezoelectric resonator - Google Patents

Abstract

(57) [Summary] A phase distortion does not occur at a frequency between a resonance frequency and an anti-resonance frequency, and P / V can be increased.
Provided are a piezoelectric ceramic composition and a piezoelectric resonator that are excellent in temperature stability of an oscillation frequency in a temperature range of 0 ° C. to + 80 ° C. and that can suppress characteristic fluctuation due to firing variation. The composition contains at least Ba, Bi and Ti as metal elements, and has a composition formula based on a molar ratio of Bi ₄ Ti ₃ O _12.
When x {(Ba _{1 -a} A _a ) TiO ₃ }, x and a are 0.5 ≦ x ≦ 0.9, 0 ≦ a ≦ 0.4, A
Is a main component that satisfies at least one of Bi, La, Nd, Gd and Pr, and contains 0.05 to 1.5 parts by weight of Mn in terms of MnO ₂ with respect to 100 parts by weight of the main component. It is.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric ceramic composition and a piezoelectric resonator, for example, a resonator, an ultrasonic oscillator, an ultrasonic motor, or a piezoelectric sensor such as an acceleration sensor, a knocking sensor, and an AE sensor. Suitable for
In particular, the present invention relates to a piezoelectric ceramic composition and a piezoelectric resonator that are preferably used for a high-frequency oscillator of an energy-entrapment type oscillator that utilizes fundamental vibration of thickness shear vibration.

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric ceramic include, for example, a filter, a piezoelectric resonator (hereinafter, a concept including an oscillator), an ultrasonic vibrator, an ultrasonic motor, a piezoelectric sensor, and the like.

Here, the oscillator is used by being incorporated in an oscillation circuit such as a Colpitts oscillation circuit for oscillating a reference signal of a microcomputer. FIG. 1 shows a Pierce oscillator circuit in which the inductor is replaced with a piezoelectric oscillator in a circuit configuration based on the Colpitts oscillator circuit.
This Pierce oscillator circuit is composed of capacitors 11 and 12, a resistor 13, an inverter 14 and an oscillator 15. Then, in the pierce oscillator circuit, in order to generate an oscillation signal, it is necessary to satisfy the following oscillation conditions.

That is, the amplification factor in the amplifier circuit composed of the inverter 14 and the resistor 13 is α, the phase amount is θ ₁ , and the feedback factor in the feedback circuit composed of the oscillator 15 and the capacitors 11 and 12 is β, the phase amount is When θ ₂ is set, the loop gain is α × β ≧ 1 and the phase amount is θ ₁ + θ ₂
= 360 ° × n (where n = 1, 2, ...).

Generally, an amplifier circuit including a resistor 13 and an inverter 14 is built in a microcomputer. The loop gain must be increased in order to obtain stable oscillation without causing erroneous oscillation or non-oscillation. In order to increase the loop gain, it is necessary to increase the P / V of the oscillator 15, that is, the difference between the resonance impedance R ₀ and the anti-resonance impedance R _a , which determines the gain of the feedback ratio β. P / V is defined as a value of 20 × Log (R _a / R ₀ ).

In order to satisfy the condition of the phase amount, the phase is inverted from about -90 ° to about + 90 ° between the resonance frequency and the anti-resonance frequency and in the vicinity of the resonance frequency and the resonance frequency. It is also important that phase distortion due to spurious vibration does not occur between anti-resonant frequencies.

Conventionally, PZT or PT type materials which have high piezoelectricity and can obtain a large P / V, for example, have been used. However, it has been pointed out that PZT and PT-based materials contain lead in an amount of about 60% of their own weight, so that acid elution may lead to lead elution and environmental pollution. Therefore, high expectations are placed on piezoelectric materials that do not contain lead.
A material system mainly composed of a lead-free bismuth layered compound is characterized by a relatively high mechanical quality factor (Qm) compared to PZT and PT based materials, and is applied as a piezoelectric material for an oscillator. Is possible.

[0008]

However, when a conventional piezoelectric ceramic composition mainly composed of a bismuth layered compound, for example, SrBi ₄ Ti ₄ O ₁₅ is used as a piezoelectric ceramic of a piezoelectric oscillator, the resonance frequency changes with temperature. The rate is ± 6000pp
Frequency tolerance of ± 30 with respect to temperature characteristics required from electronic equipment that requires high-performance control and is larger than m
There is a problem that the accuracy within 00 ppm cannot be supported.

For example, it has been known that SrBi ₄ Ti ₄ O ₁₅ is used as a basic composition for adding or substituting a rare earth element. With this composition, although the P / V is relatively large, the temperature change rate of the resonance frequency is about the same. There was a problem that it was as large as ± 6000 ppm.

When a conventional bismuth layered compound is used as a piezoelectric ceramic of a piezoelectric oscillator, a sufficient P / V cannot be obtained if the piezoelectric oscillator is miniaturized.
Poor workability and chipping (porcelain edge for resonator)
As a result, there is a problem that phase distortion due to spurious vibration occurs between the resonance frequency and the anti-resonance frequency, the phase condition is not satisfied, non-oscillation occurs, and stable oscillation cannot be obtained.

Further, in the conventional bismuth layered compound,
There is a problem that the firing temperature dependence of the porcelain density is steep, the firing temperature range of the porcelain is narrow, and the characteristic variation due to firing variations becomes large.

Therefore, according to the present invention, phase distortion does not occur at a frequency between the resonance frequency and the anti-resonance frequency, the P / V of the fundamental wave vibration of the thickness sliding vibration and the thickness longitudinal vibration can be increased, and at the same time, -20 ° C. An object of the present invention is to provide a piezoelectric ceramic composition and a piezoelectric resonator which are excellent in temperature stability of an oscillation frequency in a temperature range of up to + 80 ° C. and which can widen a firing temperature range to suppress characteristic variation due to firing variation.

[0013]

The piezoelectric ceramic composition of the present invention is a bismuth layered compound containing at least Ba, Bi and Ti as metal elements, and has a composition formula of Bi ₄ Ti ₃ O ₁₂ ·. x {(Ba _1-a A _a ) TiO ₃ }
And x is 0.5 ≦ x ≦ 0.9, 0 ≦
a ≦ 0.4, A is Bi, La, Nd, Gd and Pr
A main component satisfying at least one of the
Mn is 0.05 to 0.05 parts by weight in terms of MnO _2.
It contains 1.5 parts by weight.

According to such a piezoelectric ceramic composition, especially the thickness shear fundamental wave vibration or the thickness longitudinal fundamental wave and 3
The P / V value in the next overtone vibration can be increased, and the temperature stability of the oscillating frequency is excellent in the temperature range of -20 ° C to + 80 ° C. Further, chipping is remarkably generated during processing. Since the amount is reduced, the phase distortion caused by spurious vibration can be suppressed between the resonance frequency and the anti-resonance frequency, and the range of the firing temperature can be widened to suppress the characteristic variation due to the firing variation.

In the present invention, when A is Bi, that is,
Minutes are Bi_FourTi₃O₁₂・ X {(Ba _1-aBi_a) Ti
O₃} Is preferable. In this case,
In addition, the fundamental wave of thickness slip fundamental wave vibration and the third order overtone
It is possible to increase the P / V value in the chain vibration and
Temperature stability of oscillation frequency in the temperature range of ℃ to + 80 ℃
And improve the firing temperature and widen the firing temperature range.
It is possible to suppress the characteristic fluctuation due to the vibration.

In the piezoelectric resonator of the present invention, electrodes are formed on both main surfaces of the piezoelectric ceramic, and the piezoelectric ceramic comprises the above piezoelectric ceramic composition.

According to such a piezoelectric resonator, for example,
In the oscillator to which the thickness shear fundamental vibration is applied, the P / V becomes large, so that the oscillation allowance is increased, and the phase distortion does not occur at the frequency between the resonance frequency and the anti-resonance frequency, so that stable oscillation can be obtained. At the same time, a highly accurate oscillation with excellent temperature stability of the oscillation frequency can be obtained, and further, since the range of the firing temperature is widened, it is possible to adapt to a wide frequency range of 2 to 20 MHz in which characteristic fluctuation due to firing variation is significantly suppressed. Can be obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The piezoelectric ceramic composition of the present invention contains at least Ba, Bi and Ti as metallic elements,
The composition formula based on the molar ratio is Bi ₄ Ti ₃ O ₁₂ · x {(Ba _1-a
A _a ) TiO ₃ }, the above x and a are 0.5 ≦ x
≦ 0.9, 0 ≦ a ≦ 0.4, A is Bi, La, Nd,
A main component satisfying at least one of Gd and Pr, and 0.05 to 1.5 parts by weight of Mn in terms of MnO ₂ with respect to 100 parts by weight of the main component.

Now, the reason why the coefficient x is set in the above range will be described. In the above composition formula, the reason for setting x in the range of 0.5 ≦ x ≦ 0.9 is that x is 0.
This is because if it is less than 5, P / V becomes smaller than 55 dB. On the other hand, if x is more than 0.9, P / V will be less than 55 dB and the frequency of phase distortion will increase, so that a stable oscillator cannot be obtained.

Further, in the range of 0.5 ≦ x ≦ 0.9, the firing temperature dependency of the firing density is reduced, so that the firing temperature range can be set broadly and P /
Since it is possible to remarkably suppress the characteristic variation of V and the occurrence of phase distortion, it is possible to obtain a stable oscillator having a high yield. x is 0.6 ≦ x ≦ for the reason that P / V is made larger and phase distortion is significantly suppressed.
It is preferably 0.8.

Further, in the present invention, 0 ≦ a ≦ 0.4 is satisfied, and it is particularly desirable that 0 <a ≦ 0.4 is satisfied. By substituting a part of Ba with at least one of Bi, La, Nd, Gd, and Pr, the range of the firing temperature is widened, so that P due to variations in firing is increased.
This is because characteristic fluctuations such as / V can be significantly reduced. In particular, it is desirable to set 0.1 ≦ a ≦ 0.2 for the reason that the firing temperature range is widened and the variation in P / V characteristics due to firing variations is significantly reduced.

In particular, a part of Ba is replaced with Bi from the viewpoint that the generation of phase distortion can be remarkably reduced while the P / V is made larger than 55 dB, the firing temperature range can be widened, and the characteristic fluctuation due to firing variations can be reduced. It is desirable that the P.V.
It is desirable that 1 ≦ a ≦ 0.15. That is, the main component has a composition formula of Bi ₄ Ti ₃ O ₁₂ · x {(Ba
_1-a Bi _a) when expressed as _{TiO 3}, 0.6 ≦ x ≦} 0.
It is desirable to satisfy 8 and 0 <a ≦ 0.4, particularly 0.1 ≦ a ≦ 0.15.

Further, by adding MnO ₂ to the main component, the P / V can be greatly improved.
The content of MnO ₂ is less than 100 parts by weight of the main component. This is because if the amount is more than 5 parts by weight, the volume resistivity value decreases, a current flows during polarization and sufficient polarization cannot be performed, and the P / V of thickness shear vibration decreases. On the other hand, if the amount is less than 0.05 parts by weight, chipping easily occurs and phase distortion easily occurs. Mn enhances sinterability and increases P / V, so that MnO ₂ is added to 100 parts by weight of the main component.
It is desirable to contain 0.3 to 0.7 parts by weight in terms of conversion.

In the piezoelectric ceramic composition of the present invention, the composition
Bi as an expression_FourTi₃O₁₂・ X {(Ba_1-aA_a) Ti
O₃}, Bismuth layered as the main crystal phase
It consists of compound. That is, the piezoelectric ceramic composition of the present invention
The thing is (Ba_1-aA_a)_xBi_FourTi _{3 + x}O_{12 + 3x}To express
And (Bi₂O₂)²⁺(Α_m-1β_mO_{3m + 1})^2-Written in
In the general formula of the bismuth layered compound
And β-site and oxygen site with defects
Bismuth, which has a crystal structure of m = 4 and partially contains Mn as a solid solution
It is considered to be a layered compound. Mn is the main crystal phase
It forms a solid solution in the crystal and partly precipitates at the grain boundaries as Mn compound crystals.
There is a case. In addition, as another crystal phase,
Lower phase, perovskite phase, Bi layered compound with different structure
There may be things, but if there is a small amount, it is not a problem in terms of characteristics.
Yes.

The piezoelectric ceramic composition of the present invention contains Zr when crushed.
Zr or the like may be mixed from the O ₂ ball, but if the amount is very small, there is no problem in terms of characteristics.

A piezoelectric ceramic having the composition of the present invention is, for example,
For example, as a raw material, BaCO₃, Bi₂O ₃, MnO₂, Ti
O₂, La₂O₃, Pr₂O₃, Nd₂O₃, Gd₂O₃Empty
Various oxides or salts thereof can be used. material
Is not limited to this, carbonic acid that forms an oxide by firing
A metal salt such as salt or nitrate may be used.

These raw materials are made to have the above composition.
Average particle size distribution (D ₅₀) Is 0.3-1μ
Grind to a range of m, and mix this mixture from 850 to 1
Calcination at 000 ° C, average particle size distribution (D₅₀)But
Pulverize to a range of 0.3-1 μm, and again
Add an organic binder and wet mix to granulate.

The powder thus obtained is molded into a predetermined shape by a known press molding or the like, and the powder is heated in an oxidizing atmosphere such as air at a temperature range of 1000 to 1250 ° C.
After firing for 5 hours, a piezoelectric ceramic having the composition of the present invention is obtained.

The piezoelectric ceramic having the composition of the present invention is most suitable for the piezoelectric ceramic of the oscillator of the Pierce oscillator circuit as shown in FIG. 1, especially for the high frequency oscillator utilizing the fundamental vibration of the thickness shear vibration. Other piezoelectric resonators, ultrasonic transducers, ultrasonic motors and acceleration sensors, knock sensors, piezoelectric sensors such as AE sensors, and the like can also be used.

FIG. 2 shows a piezoelectric resonator (piezoelectric oscillator) of the present invention.
Indicates. This piezoelectric resonator is a piezoelectric ceramic 1 having the above composition.
The electrodes 2 and 3 are formed on both surfaces of. In such a piezoelectric resonator, P of the fundamental wave in thickness shear vibration is
/ V can be increased, the oscillation margin can be increased, and stable oscillation can be obtained because phase shift distortion does not occur at a frequency between the resonance frequency and the anti-resonance frequency. Further, the oscillation frequency has high temperature stability and high precision. Oscillation is obtained, especially 2 to 20 MHz
It is possible to obtain a piezoelectric oscillator that can be adapted to the frequency of.

[0031]

EXAMPLE First, as a starting material, Ba having a purity of 99.9% was used.
CO ₃ powder, Bi ₂ O ₃ powder, MnO ₂ powder, TiO ₂ powder, La ₂ O ₃ powder, Pr ₂ O ₃ powder, Nd ₂ O ₃ powder, Gd
_The composition formula of ₂ O ₃ powder based on the molar ratio is Bi ₄ Ti ₃ O as the main component.
When expressed as ₁₂ · x {(Ba _1-a A _a ) TiO ₃ }, A,
The main components of x and a having the elements and values shown in Table 1 and MnO ₂ powder were weighed and mixed so that 100 parts by weight of the main components would be the weight parts shown in Table 1.

The weighed raw material powder was put into a 500 ml polypot together with zirconia balls having a purity of 99.9% and ion-exchanged water, and mixed in a rotary mill for 16 hours.

The mixed slurry is dried in the atmosphere,
After passing through a 40-mesh, it was kept in the air at 950 ° C. for 3 hours to be calcined, and this synthetic powder was purified with Zr having a purity of 99.9%.
The powder was put into a 500 ml polypot together with O ₂ balls and ion-exchanged water and ground for 20 hours to obtain an evaluation powder.

An appropriate amount of an organic binder was added to this powder to granulate it, and the length was 25 m at 150 MPa with a die press.
m, a width of 38 mm, and a thickness of 1 mm were formed into a plate shape, and main firing was performed in the atmosphere at 1050 ° C to 1250 ° C for 3 hours to obtain a piezoelectric ceramic.

Then, after processing into a length of 6 mm and a width of 30 mm, an end face electrode for polarization in the length direction was formed and subjected to polarization treatment. After that, the polarization electrode is removed, and the thickness is about 0.
It processed with the lapping machine so that it might become 17 mm. After that, Cr-on both sides of the surface consisting of 6 mm in length and 30 mm in width
Ag was vapor-deposited, and an annealing treatment was performed at 250 ° C. for 12 hours in order to enhance the adhesion strength between the electrode and the porcelain.

After that, the electrode in a portion corresponding to no electrode is removed by etching so as to obtain the electrode structure shown in FIG. 2, and the length is 2.2 mm (L), the width is 0.9 mm (W), and the thickness is 0. A 17 mm (H) shape was processed by using a dicing saw to obtain a small oscillator for fundamental wave vibration of thickness shear vibration corresponding to 8 MHz oscillation. In FIG. 2, P indicates the polarization direction.

The characteristics of the oscillator are measured by measuring the re-impedance waveform with an impedance analyzer, and P / V at the fundamental vibration of thickness shear vibration is P / V = 20 × Log (R _a /
R ₀ ) was calculated by the equation (where R _{a is the} anti-resonance impedance and R _{0 is the} resonance impedance).

Further, according to the impedance waveform, the phase is about −90 ° to about +90 between the resonance frequency and the anti-resonance frequency.
It was investigated whether or not a phase distortion of more than 10 ° would occur in a frequency band composed of about + 90 ° phase after being inverted to 0 °. Phase distortion is evaluated by phase distortion = | (+)
Side maximum phase value-phase value locally changed from the maximum value |
When the phase distortion of more than 10 out of 100 resonators was more than 10 °, it was evaluated as x, and when it was less than that, it was evaluated as o.

Further, with the same composition, the firing temperature is 1
Decrease the temperature by 5 ° C to obtain the firing temperature dependence of density and P / V,
When the change in P / V is 5% or less even when the firing temperature changes by 15 ° C., it is Δ when it is 5 to 10%, and when it is more than 10%, the difference is P. It is shown in Table 1 as firing distribution characteristics.

Sample No. 21 is SrCO ₃ powder,
Bi ₂ O ₃ powder and TiO ₂ powder were weighed and mixed so as to be SrBi ₄ Ti ₄ O ₁₅ and baked at 1180 ° C. In addition, the sample No. 29 is SrCO ₃ powder, Bi ₂ O
₃ powder, La ₂ O ₃ powder, TiO ₂ powder (Sr _0.9 L
a _0.1 ) Bi ₄ Ti ₄ O ₁₅ Weigh and mix to obtain 11
The sample No. was fired at 70 ° C. 30 is SrCO ₃ powder,
Bi ₂ O ₃ powder, La ₂ O ₃ powder, TiO ₂ powder, SrB
i ₄ Ti ₄ O _{15 is} 100 parts by weight, and La ₂ O ₃ is 0.5.
It is added so as to be added in parts by weight and baked at 1170 ° C.

Further, the temperature change rate of the oscillation frequency is 25
-20 ℃ or +80 based on the oscillation frequency of ℃
The change in oscillation frequency at ° C was calculated by the following formula.

Fosc change rate (ppm) = {(Fosc
(Drift) 1 Fosc (25)) / Fosc (2
5)} × 100, where Fosc (dfitt) is −
Oscillation frequency at 20 ℃ or + 80 ℃, Fos
c (25) is the oscillation frequency at 25 ° C. The results are shown in Table 1.

[0043]

[Table 1]

As is clear from Table 1, the samples within the range of the present invention can have a large P / V value of the fundamental vibration in the thickness shear vibration of 55 dB or more and do not generate a phase distortion exceeding 10 °. It is found that stable oscillation can be obtained, the firing temperature range is wide, the characteristic variation due to the firing temperature change is small, and the temperature change rate of the oscillation frequency is within ± 3000 ppm, which is small.
Further, it can be seen that the rate of temperature change can be reduced by decreasing the value of x.

On the other hand, Sample No. which is a comparative example. 20 M
When n is not contained, the density of the sintered body is low and P / V
It can be seen that the value is as small as 43 dB and the phase distortion exceeds 10 °, so that stable oscillation cannot be obtained.

Sample No. 1 having a coefficient x value of 1 In the case of 1, the P / V was small, and moreover, it was found that stable oscillation could not be obtained because a large number of phase distortions exceeding 10 ° occurred in 10 out of 100 prototyped oscillators. Furthermore, the sample No. in which the value of x is larger than 0.9. 19
Even in the case of, since phase distortion easily occurs,
It can be seen that it is difficult to obtain an oscillator with poor yield and stable characteristics. In addition, the sample No. 29 and 30 are
It can be seen that the temperature change rate of the oscillation frequency exceeds ± 6000 ppm.

Further, the sample No. in which the type of A is Bi 7
In the case of, while increasing P / V to 70 dB, -20 to 8
It can be seen that the temperature change rate of the oscillation frequency of 0 ° C. is within ± 2250 ppm, which is excellent in temperature stability.

Further, a part of Ba is La, Nd, Pr,
Sample No. replaced with Gd. 13, 14, 15, 16, 1
In case of 7 and 18, x value is 0.75 and P / V is 60 dB
While having a large value as described above, the temperature change rate of the oscillation frequency of −20 to 80 ° C. is within ± 2900 ppm, which is an excellent temperature characteristic, which is a preferable characteristic as an oscillator.

FIG. 3 shows the sample No. of the present invention. The impedance and phase characteristics of Sample No. 7 are shown in FIG. The rate of temperature change of the oscillation frequency of No. 7 is shown. The sample No. of the comparative example in which the phase distortion occurred in FIG. The impedance and phase characteristics of No. 1 are shown.

As shown in FIG. 7, no large phase distortion is generated, and it can be seen from FIG. 4 that the temperature change rate of the oscillation frequency of −20 to 80 ° C. is within ± 3000 ppm, which is an excellent temperature characteristic. On the other hand, from FIG. In the case of 1, the phase between the resonance frequency and the anti-resonance frequency is about +90 after the phase is inverted from about -90 ° to about + 90 °.
In the frequency band consisting of the phase of °, shown by the symbol A,
It can be seen that a large phase distortion of which the phase exceeds 10 ° has occurred.

Further, in FIG. No. 7 and sample No. 7 having a conventionally known composition. 21 showed the firing temperature dependence of the density. 7 shows the sample No. 7 and sample No. Two
The firing temperature dependence of P / V of No. 1 was shown. From these graphs, in the sample of the present invention, since the porcelain density is high and constant in a wide firing temperature range, the porcelain density hardly changes and the P / V hardly changes even if the firing temperature varies a little. I understand.

As described above, in the piezoelectric ceramic having the composition of the present invention, in particular, P / of the fundamental wave vibration of the thickness shear vibration
V can be increased, phase distortion exceeding 10 ° does not occur between the resonance frequency and the anti-resonance frequency, and the temperature change rate of the oscillation frequency at −20 ° C. to 80 ° C. can be reduced. Furthermore, since the firing temperature dependency can be reduced, the stability of the oscillator can be improved.

Further, in FIG. 7 shows an X-ray diffractogram of 7. It can be seen from FIG. 8 that the bismuth layer compound is the main crystal phase. Sample No. 7 is B as a basic composition formula
i ₄ Ti ₃ O ₁₂ · 0.75 {(Ba _0.85 Bi _0.15 ) TiO
₃ } is shown as a combination of the bismuth layered compound and the perovskite compound. On the other hand, the bismuth layered compound has a general formula of (Bi ₂ O ₂ ) ²⁺ (α _m-1 β _m O _{3m + 1} ) ^2-
Bi ₄ Ti ₃ O ₁₂ is a bismuth layered compound of m = 3 consisting of Bi ^{3+ as} the α element and Ti ^{4+ as the} β element in the general formula, and is electrically neutral. Is kept.

The sample No. of FIG. From the X-ray diffraction pattern of No. 7, m
= 4 bismuth layered compound is recognized as the main crystal phase, it can be considered that the perovskite compound was incorporated into the bismuth layered compound of m = 3 to have crystals of m = 4. . That is, sample N
o. Α in 7 consists of the elements consisting of Bi and Ba, and β
Consists of elements consisting of Ti, it has a crystal structure of reluctant m = 4 while accompanied by defects in α site and β site and the oxygen site, specifically _{(Ba 0.85 Bi 0.15) 0. 75} Bi
It is considered that the bismuth layered compound is a solid solution of Mn in ₄ Ti _3.75 O _14.25 .

[0055]

As described above in detail, in the piezoelectric ceramic composition of the present invention, the P / V of the fundamental vibration in the thickness shear vibration is
While increasing the value, it is possible to remarkably reduce the occurrence of phase distortion exceeding 10 ° between the resonance frequency and the anti-resonance frequency, further reduce the temperature change rate of the resonance frequency, and further widen the firing temperature range. P / V characteristic variations due to firing variations can be suppressed, and high yield can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a Pierce oscillator circuit that is a prototype of a Colpitts oscillator circuit.

FIG. 2 is a schematic view of an 8 MHz oscillator.

FIG. 3 shows the sample No. of the present invention. 7 is a graph showing impedance and phase characteristics of No. 7;

FIG. 4 shows a sample No. of the present invention. 7 is a graph showing the temperature change rate of the oscillation frequency of No. 7;

5 is a sample No. of a comparative example. It is a graph showing the impedance of 1 and phase distortion.

6 is a sample No. 7 and sample No. It is a graph which shows the firing temperature dependence of the density of 21.

7] Sample No. 7 and sample No. It is a graph which shows the firing temperature dependence of P / V of 21.

8] Sample No. 7 shows a powder X-ray diffraction pattern of No. 7.

[Explanation of symbols]

l ... Piezoelectric ceramic 2, 3 ... Electrodes

Claims (3)

[Claims] 1. When at least Ba, Bi and Ti are contained as a metal element and the composition formula by molar ratio is expressed as Bi ₄ Ti ₃ O ₁₂ .x {(Ba _1-a A _a ) TiO ₃ }, x and a are 0.5 ≦ x ≦ 0.9 0 ≦ a ≦ 0.4 A is a main component satisfying at least one of Bi, La, Nd, Gd and Pr, and 100 parts by weight of the main component. Against M
A piezoelectric ceramic composition containing 0.05 to 1.5 parts by weight of n in terms of MnO ₂ . 2. A piezoelectric resonator, wherein electrodes are formed on both main surfaces of the piezoelectric ceramic, and the piezoelectric ceramic comprises the piezoelectric ceramic composition according to claim 1. 3. The piezoelectric resonator according to claim 2, which operates in a thickness shear vibration mode.