JP3203629B2 - Piezoelectric resonator element and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention, PbZrO ₃ and Pb
The present invention relates to a piezoelectric resonator element made of a solid solution with TiO ₃ .

[0002]

2. Description of the Related Art Conventionally, as a device useful for sensors and various filters, which performs mutual conversion between electric energy and mechanical energy, a piezoelectric type resonator element made of a solid solution (PZT) of PbZrO ₃ and PbTiO ₃ has been used. Are known.

However, when a piezoelectric type resonator element made of PZT is made of a single material of PZT having a specific composition, conversion sensitivity between electric energy and mechanical energy (hereinafter simply referred to as “sensitivity”). ), It is difficult to improve the dielectric characteristics, and at the same time, to make the temperature characteristics excellent in that the temperature change of the resonance frequency is small. For example, P in PZT
The relationship between mol% of bZrO ₃ and the temperature coefficient of its resonance frequency is as shown in FIG. 2 (new technology for piezoelectric ceramics, Ohm Co., Ltd., edited by Japan Electronics Materials Association).
ZT / Zr / Ti ratio (PbZrO ₃ / PbTiO ₃ ratio)
It depends greatly on. In the same figure, the temperature coefficient is near 0, and PZT having a Zr / Ti ratio exhibiting good temperature characteristics tends to have low sensitivity.

[0004] Therefore, a piezoelectric type resonator element is made of P
When manufacturing from a single material of ZT, PZT having a specific Zr / Ti ratio is selected from various PZTs in a trade-off between desired sensitivity and allowable temperature characteristics.

Further, in order to improve both the sensitivity and the temperature characteristics of the piezoelectric vibrator, a highly sensitive PZT is combined with a constant elastic body made of a material different from the PZT.

[0006]

However, when a PZT material having a specific Zr / Ti ratio is selected based on a trade-off between desired sensitivity and allowable temperature characteristics, and a piezoelectric element is manufactured from the material alone, It is inherently difficult to simultaneously improve both sensitivity and temperature characteristics. Also, in a piezoelectric type resonator element vibrator in which high-sensitivity PZT and a constant elastic body are combined, since the high-sensitivity PZT and the constant elastic body are bonded with an adhesive, the adhesive lowers temperature characteristics, Therefore, there is a problem that desired temperature characteristics cannot be obtained.

An object of the present invention is to solve the problems of the prior art as described above, and an object of the present invention is to simultaneously realize high sensitivity, desirable dielectric characteristics and excellent temperature characteristics in a piezoelectric vibrator. I do.

[0008]

SUMMARY OF THE INVENTION The inventor of the present invention has proposed a method of manufacturing a columnar piezoelectric vibrator using PZT as an element material.
If PZT having a Ti ratio is used and the distribution of the Zr / Ti ratio is made to be axially symmetric, the sensitivity and dielectric characteristics of the PZT on the outer surface will be exhibited, but the temperature characteristics will be lower than those of the PZT on the outer surface. It has been found that the characteristics are compensated for by the internal PZT, and that high sensitivity, desirable dielectric characteristics, and excellent temperature characteristics can be simultaneously achieved by appropriately selecting the PZT material on the outer surface and the PZT material on the inner side,
The present invention has been completed.

That is, the present invention relates to PbZrO ₃ and PbT
A columnar piezoelectric vibrator made of a solid solution with iO ₃ and having a regular polygonal or circular cross section, and the inner and outer surfaces thereof
Parts have different Zr / Ti ratios from each other, and the Zr / Ti
Provided is a piezoelectric vibrating piece resonator characterized in that the distribution of the / Ti ratio is axially symmetric .

In the piezoelectric type resonator element of the present invention, the outer surface has a high conversion sensitivity between electric energy and mechanical energy with respect to the inside, and the inside has a resonance frequency temperature with respect to the outer surface. Those with little change are preferred, especially
It is preferable that the inside has a temperature characteristic that compensates for the temperature characteristic of the resonance frequency of the outer surface.

There is no particular limitation on the method of manufacturing such a piezoelectric type resonator element resonator. For example, in an injection molding method, melts of PZT having different Zr / Ti ratios may be co-extruded so as to be axially symmetric. After forming PZT constituting the inside by a conventional method, an outer surface portion is formed thereon. The constituent PZT may be applied in the form of a paste using a resin binder, and then sintered to remove the resin component.

[0012]

The cross section of the piezoelectric resonator element of the present invention is a regular polygon or a circular column, and is axially symmetric.
Further, the piezoelectric type resonator element vibrator of the present invention has PZT, that is, PbT.
It is composed of a solid solution of ZrO ₃ and PbTiO _3, and the composition distribution of PZT is also axially symmetric with respect to the Zr / Ti ratio.

Therefore, the inner and outer surface portions of the columnar piezoelectric vibrating piece vibrator have Pr having different Zr / Ti ratios.
ZT, that is, PZT having different electromechanical conversion characteristics, elastic characteristics, dielectric characteristics, and temperature characteristics,
PZT having these different characteristics can affect the characteristics of the entire piezoelectric resonator element. Further, in this case, since the PZTs having such different characteristics are distributed axially symmetrically, when one of the different PZTs affects the characteristics of the piezoelectric vibrating piece resonator as a whole or when both affect the characteristics. In any case, the characteristics of the whole resonator element have the same symmetry as the outer shape.

Here, the electromechanical conversion characteristic and the dielectric characteristic of the piezoelectric vibrator are substantially in the outer surface area having a thickness of about the distance between the interdigital electrodes provided around the piezoelectric vibrator during use. It is determined by the characteristics of PZT. On the other hand, the elastic characteristic and the temperature characteristic of the piezoelectric vibrator depend on not only the outer surface region but also the characteristics of the internal PZT. Therefore, in the present invention, the outer surface portion has a Zr / T having excellent electromechanical conversion characteristics and excellent dielectric characteristics, although the temperature characteristics are poor.
An i-ratio PZT is provided, and inside the electromechanical conversion characteristics and the dielectric characteristics are inferior, but the elastic characteristics and the temperature characteristics are excellent.
When PZT having an r / Ti ratio is provided, the electromechanical conversion characteristics and the dielectric characteristics of the entire piezoelectric vibrating piece vibrator are reduced by the P on the outer surface.
The ZT has excellent properties, and the elastic properties and the temperature properties are such that the poor properties of the PZT on the outer surface are compensated for by the good properties of the PZT inside, resulting in good properties as a whole.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

By computer simulation, the following columnar piezoelectric vibrator was assumed, and its sensitivity and temperature characteristics were obtained.

That is, as shown in FIG. 1 (a), it was assumed that the piezoelectric vibrating piece vibrator 1 had a columnar shape with an outer shape of 5 × 5 × 14 mm ³ . Then, it is assumed that the cross section of the square is divided into the areas (1) to (25) as shown in FIG. 3B, and the inner areas (7), (8),
(9), (12), (13), (14), (17),
(18) and (19) are made of material A, (1), (5), (21) and (25) of the outer surface area are made of material B, and (3), (16) and (20) Made of material C,
(4), (11) and (24) are made of material D,
(6), (10) and (23) are made of material E,
(2), (15) and (22) are made of the material F, and the distribution of the materials is set to be axially symmetric. In this case, the material properties of the materials B, C, D, E and F constituting the outer surface area are different from the material A of the inner area, but are equal to each other. Further, the material A forming the inner region and the material B forming the outer surface region are isotropic, and C, D, E and F forming the outer surface region are anisotropic, respectively, as shown in FIG. It has a polarization direction indicated by an arrow.

As a specific material property of each of these materials, the material A constituting the inner region is a material characteristic of NEPEC-1 manufactured by Tokin Co., Ltd., which is one of the representative piezoelectric materials, at room temperature. It was assumed to have. The material properties of each of the materials B, C, D, E and F constituting the outer surface region were assumed to have properties expected to be exhibited when NEPEC-1 manufactured by Tokin Co., Ltd. at 50 ° C. Note that such a temperature characteristic of 50 ° C. is, for example, Landolt-Bo
rnStein, Vol. 16, Ed. T. Mitsu
i et al. Springer-Verlag, 1
981. Table 1 (2) shows specific numerical values used for the simulation as such material properties.
0 ° C.) and Table 2 (50 ° C.).

[0019]

[Table 1]

[0020]

[Table 2] In simulating the characteristics of the piezoelectric vibrator 1, it is assumed that the interdigital electrodes 2 are provided around the vibrator 1 as shown in FIG.
Then, the characteristics of the piezoelectric vibrator 1 were set to 0.5 × 0 .5 in accordance with the finite element method simulation program (television, Vol. 31, No. 6, (1977), 457).
The simulation was performed with a cube of 5 × 0.5 mm ³ as a unit. In this case, the degree of freedom of the vibration of the piezoelectric vibrator 1 is set in consideration of the symmetry of the vibrator, and the z-axis direction and the y-axis direction are made free in correspondence with the compression vibration and the bending vibration.
The axial direction was fixed. Further, one XZ plane was fixed.

The lowest resonance frequency thus determined was 7.144 kHz.

For comparison, the materials B, C, D, E and F constituting the outer surface region also have the material characteristics at 20 ° C. of NEPEC-1 manufactured by Tokin Co., Ltd., similarly to the material constituting the inner region. In this case, the lowest resonance frequency was determined to be 7.144 kHz, and no change was recognized within the calculation error. The lowest resonance frequency when all the materials had a material characteristic of 50 ° C. was found to be 7.132 kHz, which was 0.17% change.

From the above results, it was confirmed that the lowest resonance frequency greatly depends on the characteristics of the material in the internal region.

[0024]

According to the piezoelectric resonator element, excellent electromechanical conversion characteristics, desirable dielectric characteristics and excellent temperature characteristics can be simultaneously realized.

[Brief description of the drawings]

FIG. 1 is a perspective view and a cross-sectional explanatory view of a piezoelectric vibrating piece resonator of an embodiment.

FIG. 2 is a diagram showing the relationship between the composition of PZT and the temperature coefficient of the resonance frequency.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric resonator element 2 Cross finger electrode

Claims (5)

(57) [Claims] 1. A made of a solid solution of PbZrO ₃ and PbTiO _3, a columnar piezoelectric tuning bar vibrators are cross-section a regular polygon or a circle, the inner and outer surface is different Zr / Ti ratio to one another And the distribution of the Zr / Ti ratio is axially symmetric. 2. The piezoelectric sound according to claim 1, wherein the outer surface has a higher conversion sensitivity between electric energy and mechanical energy with respect to the inside, and the temperature change of the resonance frequency is smaller with respect to the outer surface with the inside. Single vibrator. 3. The piezoelectric resonator element according to claim 2, wherein the inside has a temperature characteristic for compensating for a temperature characteristic of a resonance frequency of the outer surface portion. 4. The method of manufacturing a piezoelectric vibrating piece resonator according to claim 1, wherein two or more PbZs having different Zr / Ti ratios.
The melt consisting of rO ₃ and PbTiO ₃ was converted to Zr / Ti
A production method characterized by co-extrusion by an injection molding method so that the ratio distribution is axially symmetric. 5. The method for manufacturing a piezoelectric vibrating piece vibrator according to claim 1, wherein a Zr different from the solid solution is formed on an outer surface of a solid-solution columnar formed product of PbZrO ₃ and PbTiO _3.
/ Ti of PbZrO ₃ and PbTiO ₃ and a resin paste containing a ratio applied manufacturing method characterized by sintering.