JPS5941311B2 - piezoelectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric ceramic composition, which has a high electromechanical coupling coefficient kt, an appropriate dielectric constant ε33/εo, and is easy to polarize. The present invention provides a piezoelectric ceramic that can form a resonator.

As the integration of high-frequency circuits in television receivers and the like progresses, there is a strong demand for peripheral components of integrated circuits, especially reactance circuits, to be solid-state, non-adjustable, and high-performance.

Piezoelectric ceramic resonators are expected to meet this demand. When using a piezoelectric ceramic as a high-frequency resonator, it is advantageous to use thickness longitudinal vibration in which the resonant frequency is determined by the thickness.

In order to widen the band of the resonator, it is desirable that the electromechanical coupling coefficient kt be as large as possible.

Further, in general, the dielectric constant ε33/εo is preferably smaller at high frequencies. Furthermore, from the viewpoint of manufacturing a resonator, a piezoelectric ceramic that can be easily polarized is desired. The piezoelectric ceramic made of the composition of the present invention has these characteristics. The details will be explained below based on examples. The composition tried was a composition expressed by Pbl-U, SmxTiO3,
The range is 0.075<X≦0.325.

Raw materials of PbO, Sm2O3, and TiO2 were weighed so as to have the above composition, and wet mixed in a ball mill for 17 hours.
The slurry was filtered, dried, and then calcined at about 850° C. for 2 hours. Thereafter, it was wet-pulverized using a ball mill. After drying the pulverized material, the diameter is 13m7n) and the thickness is 1.
5 mm discs were molded at a pressure of 800 to 9/1, and each was fired for 1 hour at a temperature considered optimal within the range of 1200 to 13000 C, depending on the composition. The fired porcelain was polished to a thickness of 0.3 mm, and Cr-Au electrodes were deposited on both sides. The polarization treatment was carried out in silicone oil at 20 to 150°C by applying a DC voltage of V/mm to 4 for 30 minutes.

Using this sample, 4 and ε33/ε0 were measured. k
t was determined from the resonance frequency and anti-resonance frequency of the fundamental wave. Figure 1 is a diagram showing the changes in kt and εu/εo depending on the composition.
This is a large value of 0.58.

In the range of X<0.1 and X>0.3, kt is relatively small. εu/εo increases as x increases. These results show that for compositions in the range 0.1 x 0.3, kt
=0.51~0.58, ε33/6'0=420~70
It can be seen that a piezoelectric ceramic which is advantageous as a high frequency resonator material can be obtained at 0.

FIG. 2 is a diagram showing an example of the change in kt depending on the polarization temperature of the composition of the present invention, and shows an example of the change in kt depending on the polarization temperature of the composition of the present invention. 7SmO. A large Kt can be obtained by polarizing 2TiO3 at a relatively low temperature of around 100°C.

Therefore, the composition of the present invention can be easily mass-produced on an industrial scale. Note that the Kt of conventional PbTiO3-based porcelain is 0.47, which is relatively small. In addition, with conventional materials, the polarization process requires 200
Polarization was difficult as it required a high temperature of around 30°F.

[Brief explanation of drawings]

Figure 1 shows the composition of the composition of the present invention, Kt and Tε33/
It is a figure showing the relationship of εo.

Claims (1)

[Claims] 1 Composition formula Pb_1_-_(_3_/_2_)_xSm
A piezoelectric ceramic composition represented by _xTiO_3 (0.1≦x≦0.3).