JP2001192268A - Piezoelectric porcelain composition and piezoelectric resonator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric porcelain composition which consists essentially of SrBi4Ti4O15 and has an improved electromechanical coupling coefficient (kt) and an improved resonance frequency temperature coefficient (frTC) in the temperature range of -20 to 80 deg.C and further, is capable of showing a >=20% practically feasible electromechanical coupling coefficient (kt) and a <=35 (ppm/ deg.C) practically feasible resonance frequency temperature coefficient (frTC) in the above temperature range and useful as a material of a piezoelectric ceramic element such as piezoelectric ceramic resonator, piezoelectric ceramic filter, piezoelectric ceramic oscillator or piezoelectric ceramic vibrator, and also to provide such a piezoelectric resonator using the composition. SOLUTION: This composition consists essentially of a bismuth layer compound represented by the general formula SrBi4Ti4O15, and also contains <=0.1 mol% (excluding 0 mol%) Nd per mol of Bi in the bismuth layer compound represented by the above general formula and further has a <=35 ppm/ deg.C frequency constant temperature coefficient.

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 and a piezoelectric resonator using the same, and more particularly, for example, a piezoelectric ceramic element such as a piezoelectric resonator, a piezoelectric ceramic filter, a piezoelectric ceramic oscillator, and a piezoelectric ceramic oscillator. TECHNICAL FIELD The present invention relates to a piezoelectric ceramic composition useful as a material for a piezoelectric element and a piezoelectric resonator using the same.

[0002]

2. Description of the Related Art Piezoelectric resonators, piezoelectric ceramic filters,
As piezoelectric ceramic compositions used for piezoelectric ceramic elements such as piezoelectric ceramic oscillators and piezoelectric ceramic oscillators, lead zirconate titanate (Pb (Ti _x Zr
Piezoelectric ceramic compositions containing _1-x ) O ₃ ) or lead titanate (PbTiO ₃ ) as a main component are widely used. However, in piezoelectric ceramic compositions containing lead zirconate titanate or lead titanate as a main component, the composition contains a large amount of lead, and the uniformity of the product is reduced due to evaporation of lead oxides in the manufacturing process. There was a problem of doing. A piezoelectric ceramic composition containing no or only a small amount of lead in its composition is preferred in order to prevent a reduction in product uniformity due to evaporation of lead oxides during the production process. In contrast,
A piezoelectric ceramic composition containing a bismuth layered compound such as SrBi ₄ Ti ₄ O ₁₅ as a main component does not contain a lead oxide in the composition, and thus does not have the above-described problems.

[0003]

However, SrB
i ₄ In Ti ₄ O piezoelectric ceramic _{composition 15} or the like as a main component, the piezoelectric resonator conventionally, a piezoelectric ceramic filter, zirconate titanate used in the piezoelectric ceramic element such as a piezoelectric ceramic oscillator and a piezoelectric ceramic oscillator The electromechanical coupling coefficient kt is smaller than that of the piezoelectric ceramic composition containing lead oxide or lead titanate as a main component, and the temperature change rate frTC of the resonance frequency from -20 ° C to 80 ° C shown below.
Has not been widely used. frTC = (fr (max) -fr (min)) / (fr
(20 ° C) · 100) fr (max): Highest resonance frequency in the temperature range from -20 ° C to 80 ° C fr (min): Lowest resonance frequency in the temperature range from -20 ° C to 80 ° C fr (20 ° C) : Resonance frequency at 20 ° C

[0004] Therefore, the main object of the present invention is to provide an S
The electromechanical coupling coefficient kt of the piezoelectric ceramic composition containing rBi ₄ Ti ₄ O ₁₅ as a main component and the temperature change rate frTC of the resonance frequency from −20 ° C. to 80 ° C. are improved so that the electromechanical coupling coefficient can be put to practical use. Piezoelectric resonators, piezoelectric ceramic filters, piezoelectric ceramic oscillators, and piezoelectric ceramic elements such as piezoelectric ceramic vibrators that exhibit kt (20% or more) and the temperature change rate frTC (35 or less) of the resonance frequency are useful as piezoelectric ceramics. An object of the present invention is to provide a composition and a piezoelectric resonator using the same.

[0005]

The piezoelectric ceramic composition according to the present invention is a piezoelectric ceramic composition mainly containing a bismuth layered compound composed of at least Sr, Bi, Ti and O, wherein Nd is contained in the main component. A piezoelectric ceramic composition characterized by containing 0.1 mol or less (not including 0) with respect to 1 mol of Bi and having a frequency constant temperature change rate of 35 ppm / ° C. or less. Further, the piezoelectric ceramic composition according to the present invention is a piezoelectric ceramic composition containing a bismuth layered compound represented by the general formula SrBi ₄ Ti ₄ O ₁₅ as a main component. And 0.1 mol or less (not including 0), and the rate of temperature change of the frequency constant is 35 ppm / ° C. or less. In the piezoelectric ceramic composition according to the present invention, N contained in the main component
A part of d may be substituted with Y. In the piezoelectric ceramic composition according to the present invention, Mn may be contained in an amount of 1.5% by weight or less (not including 0) in terms of MnCO ₃ .
A piezoelectric resonator according to the present invention includes an excitation layer made of the piezoelectric ceramic composition according to the present invention, and vibrating electrodes formed on both main surfaces of the excitation layer, and has an nth-order longitudinal vibration harmonic (where n is 1). (A natural number other than). The main component in the piezoelectric ceramic composition according to the present invention is represented by a general formula SrBi ₄ Ti ₄ O ₁₅ ,
The molar ratio of each element may be slightly different. In general, Nd ₂ O ₃ powder contains impurities, but the ratio of Bi to Nd in the present invention is the ratio excluding the impurities, that is, the ratio of Bi element to Nd element.

In the piezoelectric ceramic composition according to the present invention, the content of Nd is set to 0.1 mol per 1 mol of Bi.
The value of 1 or less (not including 0) means that if it is more than this, the electromechanical coupling coefficient kt decreases, and a practical electromechanical coupling coefficient kt cannot be obtained, or a polarizable ceramic Is not obtained. Also, Takahashi et al., In Japanese Patent Application No. 48-85292, SrBi ₄ Ti ₄ O ₁₅
It has been clarified that the electromechanical coupling coefficient kt is improved by containing 0.005 to 0.7% by weight of Mn in terms of MnO in a piezoelectric ceramic composition containing as a main component. Even in a piezoelectric ceramic composition, that is, a piezoelectric ceramic composition containing an appropriate amount of Mn in a piezoelectric ceramic composition as a main component, the effect of the present invention is effective. fr
A useful piezoelectric ceramic composition having a small TC can be obtained. In the invention according to claim 4, the content of Mn is set to 1.5% by weight or less (not including 0) in terms of MnCO _3. This is because the effect of adding Mn cannot be obtained. Further, since Nd is selected, in addition to the improvement of the electromechanical coupling coefficient kt, the temperature change rate frTC of the resonance frequency becomes particularly small, so that, for example, the piezoelectric resonator, the piezoelectric ceramic filter, the piezoelectric ceramic oscillator, and the piezoelectric A piezoelectric ceramic composition which is more useful as a material for a piezoelectric ceramic element such as a ceramic vibrator can be obtained.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.

[0008]

(Embodiment 1) First, as a starting material,
And SrCO_Three, Bi_TwoO_Three, TiO_Two, Ce_TwoO_Three,
Pr_TwoO_Three, Nd_TwoO_Three, Dy_TwoO_Three, Er_TwoO_Three, Y
b_TwoO_ThreeAnd MnCO_ThreeAre prepared, and these are composed (S
r_1-xM_x) Bi_FourTi_FourO_Fifteen+ Y weight% MnCO
_Three(M is Ce, Pr, Nd, Dy, Er and Yb
Anyway? 0 ≦ x ≦ 0.45, 0 ≦ y ≦ 1.6. ) Becomes
And wet mixing using a ball mill for about 4 hours
Thus, a mixture was obtained. After drying the resulting mixture, 7
The calcined product was obtained by calcining at 00 to 900 ° C. then,
After coarsely pulverizing this calcined product, add an appropriate amount of organic binder
4 hours wet pulverization using a ball mill, 40 mesh
The particle size was adjusted through a sieve. Then, add this to 100
0kg / cm^Two12.5mm in diameter and 2mm in thickness
Molded into a disk of 1150-1250 ° C in air.
Then, a disc-shaped porcelain was obtained. This magnet
Silver paste on the surface (both main surfaces)
After coating and baking to form silver electrodes, 150-200 ° C
DC voltage of 5-10 kV / mm in insulating oil of 10
Applied for ~ 30 minutes to perform polarization treatment, piezoelectric ceramic (sample)
I got Then, for the obtained sample, electromechanical coupling
Measures coefficient kt and temperature change rate frTC of resonance frequency
did. Table 1 shows the results. Table 1 shows each sample.
And the numerical values of x and y in the composition of
Show. In Table 1, one-fourth of x in the above composition formula is
That is, x / 4 is Bi content per 1 mol of M (m
ol). Table 1
Indicates the frequency constant temperature change rate for each sample. Week
The wave number constant is defined as frequency constant (Hz · m) = element thickness (electron
It is expressed by (distance between poles) × resonance frequency. And the frequency constant
The rate of change of several temperatures is defined below. Frequency constant temperature change rate = (frequency constant (max)-frequency
Numerical constant (min)) / (Frequency constant (20 ° C.) · 10
0) Frequency constant (max): circumference from -20 ° C to 80 ° C
Maximum value of wave number constant Frequency constant (min): circumference from -20 ° C to 80 ° C
Minimum value of wave number constant Frequency constant (20 ° C): Frequency constant at 20 ° C

[0009]

[Table 1] The * mark in the sample number column indicates that the sample is outside the scope of the present invention.

Example 2 In Example 2, the composition (Sr
_{1- (x + z)} Nd _x Y _z ) Bi ₄ Ti ₄ O ₁₅ + y wt% Mn
The procedure was the same as in Example 1 except that the sample was weighed to obtain CO ₃ . Table 2 shows the results of Example 2.

[0011]

[Table 2]

As shown in Tables 1 and 2, each of the samples according to the embodiments of the present invention has an electromechanical coupling coefficient kt of not less than 20%, which is a practical level, and the temperature change rate frTC of the resonance frequency. Is at a practical level of 35 or less, so that the piezoelectric ceramic composition is particularly useful as a material for a piezoelectric ceramic element such as a piezoelectric resonator, a piezoelectric ceramic filter, a piezoelectric ceramic oscillator, and a piezoelectric ceramic oscillator. it is obvious. Further, as shown in Tables 1 and 2, since Nd was contained, that is, Samples No. 2, 3, 4, 7,
At 8, 11, 12, 31, 32 and 33, it is clear that a useful piezoelectric ceramic having a particularly small temperature change rate frTC of the resonance frequency can be obtained.

Incidentally, the piezoelectric ceramic composition according to the present invention is not limited to the composition of the above-mentioned embodiment, but is effective within the scope of the invention.

In the above embodiment, the electromechanical coupling coefficient kt and the temperature change rate frTC of the resonance frequency have been described with respect to the thickness longitudinal vibration of the disc-shaped piezoelectric ceramic vibrator, but the effects of the present invention are as follows. Not limited to the thickness longitudinal vibration of the disc-shaped piezoelectric ceramic vibrator, other piezoelectric ceramic elements such as a thickness shear vibration and a harmonic of the thickness longitudinal vibration, such as a piezoelectric resonator, a piezoelectric ceramic filter, a piezoelectric ceramic oscillator, etc. The other vibration modes used in the above are also effective as in the case of the thickness longitudinal vibration.

FIG. 1 is a perspective view showing an example of a piezoelectric ceramic vibrator according to the present invention, and FIG. 2 is a schematic sectional view thereof. Piezoelectric ceramic vibrator 1 shown in FIGS. 1 and 2
0 includes, for example, a rectangular parallelepiped piezoelectric ceramic 12. The piezoelectric ceramic 12 includes two piezoelectric ceramic layers 12a and 12b as excitation layers. These piezoelectric ceramic layers 12a and 12b
Comprises the piezoelectric ceramic composition according to the present invention described above,
It is laminated and integrally formed. Further, these piezoelectric ceramic layers 12a and 12b are polarized in the same thickness direction as shown by arrows in FIG.

Between the piezoelectric ceramic layers 12a and 12b,
At its center, for example, a circular vibration electrode 14a is formed,
For example, a T-shaped extraction electrode 16a is formed from the vibration electrode 14a to one end surface of the piezoelectric ceramic 12. On the surface of the piezoelectric ceramic layer 12a, for example, a circular vibrating electrode 14b is formed at the center thereof.
From the other end of the piezoelectric ceramic 12, a T-shaped extraction electrode 16b is formed, for example. Further, the piezoelectric ceramic layer 12
b, for example, a circular vibrating electrode 14
c is formed, and for example, a T-shaped extraction electrode 16c is formed from the vibrating electrode 14c to the other end surface of the piezoelectric ceramic 12.

The lead wire 18 is connected to the extraction electrode 16a.
One external terminal 20a is connected via a, and the other external terminal 20b is connected to the extraction electrodes 16b and 16c via another lead wire 18b.

The present invention relates to a piezoelectric ceramic vibrator other than the above-described piezoelectric ceramic vibrator 10, a piezoelectric resonator,
The present invention is also applied to other piezoelectric ceramic elements such as a piezoelectric ceramic filter and a piezoelectric ceramic oscillator.

[0019]

According to the present invention, SrBi ₄ Ti ₄ O
_15. A piezoelectric ceramic composition comprising ₁₅ as a main component, wherein the electromechanical coupling coefficient kt is improved to 20% or more and the temperature change rate of the resonance frequency is improved to 35 or less, for example, a piezoelectric resonator, a piezoelectric ceramic filter, A piezoelectric ceramic composition useful as a material for a piezoelectric ceramic element such as a piezoelectric ceramic oscillator and a piezoelectric ceramic oscillator, and a piezoelectric resonator using the same are obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a piezoelectric ceramic vibrator according to the present invention.

FIG. 2 is an illustrative sectional view of the piezoelectric ceramic vibrator shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric ceramic vibrator 12 Piezoelectric ceramic 12a, 12b Piezoelectric ceramic layer 14a, 14b, 14c Vibrating electrode 16a, 16b, 16c Leading electrode 18a, 18b Lead wire 20a, 20b External terminal

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yo Ando 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Koichi Hayashi 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Stock Company Murata Manufacturing

Claims (5)

[Claims] 1. A piezoelectric ceramic composition containing a bismuth layered compound composed of at least Sr, Bi, Ti and O as a main component, wherein Nd is 0.1 mol or less (including 0) with respect to 1 mol of Bi in the main component. A) a piezoelectric ceramic composition, characterized in that it contains and has a temperature change rate of frequency constant of 35 ppm / ° C. or less. 2. A piezoelectric ceramic composition containing a bismuth layered compound represented by the general formula SrBi ₄ Ti ₄ O ₁₅ as a main component, wherein Nd is contained in an amount of 0.1 mol or less with respect to 1 mol of Bi in the main component. ), And a rate of temperature change of a frequency constant of 35 ppm / ° C or less. 3. The piezoelectric ceramic composition according to claim 1, wherein a part of Nd contained in the main component is replaced with Y. 4. The piezoelectric ceramic composition according to claim 1, wherein the composition contains 1.5% by weight or less (excluding 0) of Mn in terms of MnCO ₃ . . 5. An nth-order longitudinal vibration harmonic, comprising: an excitation layer comprising the piezoelectric ceramic composition according to claim 1; and vibration electrodes formed on both main surfaces of the excitation layer. A piezoelectric resonator characterized by exciting a wave (n is a natural number other than 1).