JPS63132491A - Manufacturing method of piezoelectric ceramic - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of manufacturing piezoelectric ceramics, particularly for improving dielectric loss.

[Prior art and its problems]

In piezoelectric ceramics for forming a vibrator, electrodes for polarization are usually formed after sintering, and the electrodes are removed after polarization.

Thereafter, polishing is performed to set the resonance frequency, and after adjusting the thickness, electrodes for the vibrator are formed on the t-plane, and the vibrator is cut and separated into the size of each vibrator. Note that there are cases where a polarization electrode is formed on the entire main surface of the piezoelectric ceramic, and the electrode is partially left without being removed and used as an electrode for a vibrator.

By the way, the most important characteristic of such piezoelectric ceramics is dielectric loss, and it is desirable that this dielectric loss be small in order to increase vibration efficiency. Furthermore, as the humidity increases, the dielectric member increases, but it is important to minimize this change in order to stabilize the frequency characteristics.

Conventionally, it was adjusted by the composition of the piezoelectric ceramic and the conditions during sintering, but there was a large variation depending on the loft, and there was a limit to improving the numerical value, so a new method was sought.

As a result of various studies, the inventors focused on pores of several micrometers in grain boundaries on the surface of piezoelectric ceramics after sintering, and found that dielectric loss could be reduced by cooling these pores. succeeded in.

〔the purpose〕

An object of the present invention is to provide a method for manufacturing a piezoelectric ceramic that can reduce dielectric loss and its change much smaller than conventional methods, and includes a step of diffusing glass from the surface of the piezoelectric ceramic.

[Technical means to solve problems]

The method for manufacturing a piezoelectric ceramic of the present invention includes providing a glass film on the surface of the piezoelectric ceramic before forming electrodes for polarization,
It is characterized by providing a step in which glass is diffused by heat treatment.

[Example] Hereinafter, a description will be given with reference to FIG. 1, which is a process diagram showing an example of the piezoelectric ceramic manufacturing method of the present invention. The right side of FIG. 1 shows a slightly exaggerated side view of the piezoelectric ceramic corresponding to the process on the left.

Piezoelectric ceramic 1 after sintering made of PZT porcelain in step 1
0 is processed into a fixed size and shape by polishing. This first step 1 may be dicing, but can be omitted if the dimensions of the piezoelectric ceramic 10 are within a predetermined range.

Next, in step 2, a paste 11 containing glass, a so-called glass paste, is applied by printing to the main surface of the piezoelectric ceramic 10 to form a glass film several tens of microns thick. Such a paste 11 has lead glass as its main component, and for example, it may be used in the form of a paste of vitreous free-glue commercially available from Toshiba Glass Co., Ltd. under the trade name GSP220A503.

Then, in step 3, heat treatment is performed for 110 minutes at 750"C in an air atmosphere. Through this heat treatment, the glass is diffused into the piezoelectric ceramic 10, and the pores are closed.

Next, in step 4, electrodes 12 for polarization are formed on the opposing sides of the piezoelectric ceramic lO, and in step 5, polarization treatment is performed using a DC voltage of about 3 KV/mm.

In step 6, the electrode 12 is removed, and in step 7, the thickness of the piezoelectric ceramic 10 is adjusted by polishing, and the resonance frequency is set.

Then, in step 8, electrodes 13 are formed on the entire main surface of the piezoelectric ceramic 10.

Although subsequent steps are not shown in the drawings as they are not essential parts of the present invention, unnecessary parts are removed from the electrode 13 to form an electrode for a vibrator, and then the piezoelectric ceramic 10 is cut and separated into individual vibrators. do.

Note that the paste 11 in the example has lead glass as the main component, but may also have soda glass or silicate glass as the main component. The temperature of the heat treatment may be higher than the melting point of the glass, and can be carried out by adjusting the time within the range of approximately 450 to 800°C. Alternatively, the glass film may be provided by dipping the piezoelectric ceramic 10 in a molten glass solution.

〔effect〕

Figure 2 shows that the dielectric...
It is a characteristic diagram obtained by measuring the piezoelectric ceramic 10 (
This is a comparison of a conventional piezoelectric ceramic (with glass diffusion) and a conventional piezoelectric ceramic (without glass diffusion). tanδ is IV, IKHz
Measured under the following conditions.

The conventional product has a distribution between 12 and 18%, but the product of the present invention has a small value of 5% or less, and the effect of the production method of the present invention is remarkable.

Furthermore, Fig. 3 is a characteristic diagram showing the results of a humidity test at 60°C, 95% humidity, and 100 hours in terms of janδ, and the distribution range of the products manufactured by the manufacturing method of the present invention marked with ○ is that before the test.
After the test, all values were within 5% and there was almost no change. However, in the conventional case marked with an X, the distribution centered on 12% before the test increases to a distribution centered on 60% after the test, and the range of the distribution also widens.

As described above, according to the manufacturing method of the present invention, the dielectric loss and its moisture resistance can be greatly improved, and the distribution of these characteristics can also be narrowed, which is advantageous in terms of quality control. In addition, it is much easier to improve the characteristics by adjusting the manufacturing conditions after sintering than by controlling the composition of the piezoelectric ceramic or the conditions during sintering.

Although not particularly shown, the change in insulation resistance after the humidity test is much smaller than that of the conventional one. The physical strength of the piezoelectric ceramic is also about 1.5 times stronger.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the method for manufacturing a piezoelectric ceramic according to the present invention, and FIGS. 2 and 3 are characteristic diagrams comparing the piezoelectric ceramic according to the present invention and a conventional piezoelectric ceramic, respectively. 10: Piezoelectric ceramic 11 Niglass film 12.13:
electrode

Claims (1)

[Claims] 1. A method for manufacturing a piezoelectric ceramic, comprising the steps of providing a glass film on the surface of the piezoelectric ceramic before forming electrodes for polarization, and diffusing the glass through heat treatment.