JPH09162680A - Piezoelectric vibrator and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the highly reliable piezoelectric vibrator and its manufacture in which production of distortion and an alterated layer due to processing after polarization and characteristic deterioration caused by dispersion in the uniformity in PZT group piezoelectric materials are not caused. SOLUTION: The piezoelectric vibrator is shaped so that an oxygen gas is penetrated inside by thermal diffusion and is made of a PZT group piezoelectric material heat-treated for 30min or over at a temperature lower than a prescribed sintering temperature by 50 to 500 deg.C in an atmosphere with 10% of oxygen concentration or over. A thick sintering body is cut to have a thickness of 2mm or below and the resulting body is heat-treated under the condition above, and a thin sintering body of 2mm or below is sintered and heat-treated under the condition above, and then the processed body is formed to be the piezoelectric vibrator after polarization, polishment, electrode vapor-deposition and cutting process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, a filter for communication equipment, a piezoelectric vibrator such as an oscillator, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in order to finish a PZT type piezoelectric material containing lead zirconate titanate as a main component as a piezoelectric vibrator, a thick sintered body is polarized as it is, or sliced and then polarized. Further, it was assembled after material processing such as slicing and cutting.

[0003]

However, in such a conventional method, since the PZT-based piezoelectric material is processed by polarization to excite its piezoelectricity and then processed, processing strain and an altered layer on the processed surface cause piezoelectric vibration. There is a possibility that the characteristics and reliability of the child may deteriorate.

Further, since the PZT-based piezoelectric material having a large shape is processed into a minute resonator, there is a problem that the homogeneity variation in the fired PZT-based piezoelectric material directly leads to the characteristic variation of the resonator. .

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a piezoelectric vibrator having a highly reliable PZT-based piezoelectric material.

[0006]

In order to solve this problem, the piezoelectric vibrator of the present invention has a thickness of 2 mm or less so that oxygen can penetrate into the inside by thermal diffusion, and the oxygen concentration is 10%.
50 to 50 from the predetermined peak firing temperature in the above atmosphere
PZ heat-treated for 30 minutes or longer at a temperature within 0 ° C lower range
It is composed of a T-based piezoelectric material.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is
By processing a sintered body of a PZT-based piezoelectric material having a large shape by slicing or the like and then heat-treating it while supplying oxygen, it is possible to improve the processing strain and the altered layer, and the characteristic variations caused by the sintered body site Can be made uniform. Furthermore, by firing a thin molded body containing a large amount of an organic binder and the like, and subsequently subjecting it to heat treatment while supplying oxygen, it is possible to obtain a PZT-based piezoelectric material having good characteristics and small variations with good mass productivity.

(Embodiment 1) Raw materials were weighed so as to have a predetermined composition, mixed in a ball mill, and then calcined at an optimum calcining temperature. After pulverization, a PVA-based binder solution was added and granulated to form a block shape, and the optimum firing peak temperature was 120.
It was baked at 0 ° C. The block-type sintered body of the PZT-based piezoelectric material thus obtained was cut into a square plate having a thickness of 0.3 mm, and the furnace was heated at 1100 ° C., which is 100 ° C. lower than the firing peak temperature, in an atmosphere with an oxygen concentration of 20%. It heat-processed for 1 hour. After that, in order to evaluate the characteristics as a piezoelectric vibrator, this heat-treated square plate and a non-heat-treated square plate of the same sintered body were polarized by providing full-face electrodes on both sides, and then the electrodes on both sides were removed. A large number of spot electrodes were vapor-deposited on the substrate and then cut to fabricate an energy trap type piezoelectric vibrator. The homogeneity and characteristic variation of the PZT-based piezoelectric material were evaluated from the variation of loop gain measured using these piezoelectric vibrators. FIG. 1 shows the loop gain distribution of the piezoelectric vibrator manufactured from the heat-treated square plate. FIG. 2 shows a loop gain distribution of a piezoelectric vibrator manufactured from an unheated rectangular plate of the same sintered body. As is clear from the figure, the heat-treated one has a smaller loop gain variation width than the non-heat-treated one, and the characteristic level is improved.
It can be seen that the homogeneity and characteristic variation of the PZT-based piezoelectric material are improved. However, if the difference between the heat treatment temperature and the optimum firing temperature is smaller than 50 ° C or higher than the optimum firing temperature, lead monoxide, which is the main component of the PZT-based piezoelectric material, scatters from the surface of the square plate, resulting in poor homogeneity and characteristics. It is not preferable because it causes variations. Also, the oxygen concentration in the furnace during the heat treatment is 1
If it is less than 0%, the characteristics are improved, but a change over time occurs, and a highly reliable piezoelectric vibrator cannot be obtained.
Furthermore, if the heat treatment time is shorter than 30 minutes, the effect is small even if the heat treatment temperature is high, and neither the characteristic improvement nor the variation improvement was confirmed by the evaluation with the piezoelectric vibrator. Also, the thickness is 2 mm
When the thickness became thicker, even if the heat treatment was carried out, the permeation into the interior due to thermal diffusion of oxygen was not sufficiently carried out, and no remarkable improvement in the characteristics was observed.

(Embodiment 2) FIG. 3 shows a manufacturing process diagram of a second embodiment of the present invention. The raw materials are weighed so as to have a predetermined composition and mixed by a ball mill, and then the optimum calcination temperature is 800
It was calcined at ℃. After pulverization, a PVA-based binder solution was added and granulated to form a block shape having a thickness of 10 mm, which was then fired at a firing temperature of 1220 ° C. The block-type sintered body of the PZT-based piezoelectric material obtained in this manner was sliced into a square plate having a thickness of 0.3 mm, and stacked and packed in a sheath at a temperature 100 ° C. lower than the firing temperature in a furnace. Heat treatment was performed for 1 hour in an atmosphere with an oxygen concentration of 20%. Next, after forming electrodes on both sides of the square plate and subjecting them to polarization, both sides were polished to a thickness of 0.2 mm and a large number of spot electrodes were deposited. Then, it was cut into a predetermined shape to manufacture an energy trap type piezoelectric vibrator. For comparison, a block type sintered body of the same PZT-based piezoelectric material was sliced, and the polarization treatment, polishing, electrode deposition, and cutting were performed without heat treatment, and a piezoelectric vibrator similar to the above was manufactured. When the characteristics of the respective piezoelectric vibrators thus obtained were evaluated, there were large differences in the characteristic levels and variations, and the piezoelectric vibrators of the present invention showed no deterioration in characteristics due to heat treatment, and the loop gain value It was confirmed that the improvement and the width of variation were reduced. That is, even with the same PZT-based piezoelectric material, by using the manufacturing method of the present invention, the characteristics were improved, the production yield was improved, and a highly reliable piezoelectric vibrator could be obtained with good mass productivity.

(Embodiment 3) FIG. 4 shows a manufacturing process diagram of a third embodiment of the present invention. The raw materials were weighed so as to have a predetermined composition, mixed by a ball mill, and then calcined at an optimum calcining temperature. After pulverization, a PVA-based binder solution and a dispersant were added and kneaded, followed by extrusion molding to a thickness of 0.6 mm. Next, it was cut into a predetermined sheet shape, stacked and filled in the sheath, and fired at 1150 ° C. in the air atmosphere at the optimum firing temperature. Further, subsequently, a heat treatment was performed at a temperature lower than the firing temperature by 100 ° C. in an atmosphere having an oxygen concentration of 30% in the furnace for 1 hour. A sheet-type sintered body of the PZT-based piezoelectric material thus obtained and a sheet-type sintered body of the PZT-based piezoelectric material that has not been heat-treated were manufactured in the same manner as in Embodiment 2 and a comparative evaluation was conducted. It was confirmed that the characteristics were improved and stabilized by the heat treatment, and the characteristic deterioration due to the processing after the polarization treatment and the characteristic variation due to the residual binder were improved. The piezoelectric vibrator according to the present invention is not limited to the first embodiment, and can be changed within the scope of the gist. Furthermore, the method for manufacturing a piezoelectric vibrator according to the present invention is
The present invention is not limited to Embodiments 2 and 3, and in particular PZT
-Based piezoelectric material mixing method, granulation method, molding method, processing method,
Needless to say, the method of filling the sheath and the method of forming the electrodes are arbitrary except the description in the embodiment, and the effects of the present invention are effective.

[0011]

As described above, the present invention provides a piezoelectric vibrator,
Heat treatment for 30 minutes or more at a temperature of 50 to 500 ° C. lower than a predetermined firing peak temperature in an atmosphere having an oxygen concentration of 10% or more so that oxygen can penetrate into the inside by thermal diffusion. By using the PZT-based piezoelectric material described above, it is possible to obtain a highly reliable piezoelectric vibrator with a small variation in characteristics at a high yield. Further, by subjecting a sintered body of a PZT-based piezoelectric material having a larger shape to thickness processing such as slicing and then heat-treating it while supplying oxygen, it is possible to improve processing strain and an altered layer, and characteristics generated by the sintered body site. The variation can be made uniform. Further, by firing a thin molded body containing a large amount of an organic binder and the like, and subsequently performing heat treatment while supplying oxygen, a PZT-based piezoelectric material having high characteristics and small variations can be obtained with good mass productivity, and high reliability can be obtained. The piezoelectric vibrator can be obtained with high yield.

[Brief description of the drawings]

FIG. 1 is a diagram showing a distribution of loop gain characteristics of a piezoelectric vibrator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of loop gain characteristics of a conventional piezoelectric vibrator.

FIG. 3 is a flowchart of manufacturing steps of the piezoelectric vibrator according to the second embodiment of the present invention.

FIG. 4 is a flowchart of a manufacturing process of the piezoelectric vibrator according to the third embodiment of the present invention.

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Claims (3)

[Claims] 1. A shape having a thickness of 2 mm or less, after firing at a predetermined peak temperature, and then in an atmosphere having an oxygen concentration of 10% or more at a temperature within a range of 50 to 500 ° C. lower than the predetermined peak firing temperature for 30 minutes. A piezoelectric vibrator composed of a PZT-based piezoelectric material that has been subjected to the above heat treatment. 2. A PZT-based piezoelectric material fired at a predetermined peak temperature is sliced to a thickness of 2 mm or less, and then 50 to 500 ° C. lower than the predetermined peak firing temperature in an atmosphere having an oxygen concentration of 10% or more. A method for manufacturing a piezoelectric vibrator, which is formed by performing heat treatment for 30 minutes or more at a temperature within the range. 3. A PZT-based piezoelectric material formed into a sheet having a thickness of 2 mm or less is fired at a predetermined peak temperature, and then 50% from a predetermined firing temperature in an atmosphere having an oxygen concentration of 10% or more.
A method for manufacturing a piezoelectric vibrator, which is formed by performing heat treatment for 30 minutes or more at a temperature within a range of lower by 500 ° C to 500 ° C.