JPS5943104B2 - piezoelectric ceramic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric ceramic, which has a large electromechanical coupling coefficient, a large frequency constant Nt, and a dielectric constant ε33/εo.
The object of the present invention is to provide a material that has an appropriate value and is easy to sinter, and that can be used to construct a broadband resonator for high frequencies.

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.

When the frequency is determined, the thickness of the resonator is the frequency constant Nt
is proportional to. In terms of mechanical strength and processing accuracy, there is a limit to the thickness at high frequencies. The larger Nt is, the more advantageous it is for high frequency applications. In order to widen the band, it is desirable that the electromechanical coupling coefficient kt be as large as possible. Further, the smaller the dielectric constant ε33/εo, the better. Furthermore, it would be advantageous if the porcelain could be fired easily, for example over a wide range of firing temperatures. The porcelain having the composition of the present invention has these characteristics.

The tried composition is in the range of 0.075<X<0.325 in the formula expressed by Pbl-xNdxTi03.

Raw materials of PbO, TiO2, and Nd2O3 were weighed so as to have the above composition, and wet mixed in a ball mill for 17 hours.
The slurry was filtered and dried, then calcined at about 850° C. for 2 hours, and wet-pulverized again using a ball mill. After drying the crushed material, the diameter is 13mm) and the thickness is 1.5w.
tm discs were molded at a pressure of 800 kg/Cd, and each was fired for 1 hour at a temperature considered to be optimal within the range of 1150'' to 1350°C depending on the composition.The firing temperature range for porcelain with this composition is as described above. ±3 from a certain value in the temperature range
It only needs to be within 0°C, which is wider than, for example, PbTiO3 porcelain, which is within ±20°C. The fired porcelain has a thickness of 0.
It was polished to 3 mm, and Cr-Au electrodes were deposited on both sides.

Polarization was performed at 150° C. and 4 KV/mwL for 30 minutes. Using this sample, kt and ε33/εo were measured. kt was determined from the resonance and anti-resonance frequencies of the fundamental wave. The figure shows changes in ε33/εo, kt, and Nt depending on the composition.

kt is 0.100≦X≦0.300, 0.52 to 0
．． It's 55 and quite large. Nt increases as X increases, and is 2160H2-m or more when X>0.100. ε33/εo increases as X increases. As a result, at a composition of 0.100≦x≦0.300, K
t-0.52~0.55, NtT-2170~2460
It can be seen that a material advantageous as a high frequency resonator material can be obtained at Hz-m and ε33/εo -580 to 750.

Moreover, the firing temperature range of this porcelain is wide at ±30°C. Compared to the value of PbTiO3, a high frequency material, Kt. Nt,
Very good in firing temperature range. In addition, Pb
For TlO3, Kt is 0.47 and Nt is 2160Hz-
m, the firing temperature range is ±20°C.

[Brief explanation of drawings]

The T diagram shows the composition of the composition of the present invention and ε33/ε0. kt, Nt
Indicates the relationship between

Claims (1)

[Claims] 1 In the composition represented by the formula Pb_1-(3/2)_xNd_xTiO_3, 0.100≦x≦0.300
A piezoelectric ceramic material characterized by having a composition in the range of.