JPS5937874B2 - piezoelectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric ceramic composition, which can constitute an energy confinement resonator related to thick vertical vibration, has a large electromechanical coupling coefficient for thick vertical vibration, and has a wide band high frequency. The present invention aims to provide a ceramic piezoelectric material for 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 thick vertical vibration.

In this case, it is necessary to remove unnecessary vibrations, and the energy confinement method is effective for this purpose. To apply this energy confinement method to the fundamental resonance of thick vertical vibration (
It is necessary that Poisson's ratio σ given by 2-C23,.S4)/(2-2C93.S24) is larger than l/3. However, C93 is an elastic stiffness related to the thickness vertical vibration, and 544 is an elastic compliance related to the thickness vertical vibration.

In order to use it as a wideband filter, it is necessary that kt be large. Until now, there have been few examples of measurement of σ, and the composition range with σ of 1/3 or more has not been clarified.

A material with kt of 51% or more and σ of 1/3 or more has not been obtained so far. The present invention is 1/3
It has σ of above and kt of 54% or above, and provides a high frequency broadband filter material.
3Nb2/3) 03+(1-x-y)PbTi03+
yPbZ to 03]+ZCaF2 (however, 0.025≦
X≦0.125, 0.372≦y≦0.618, 0.0
This is based on the discovery that the composition of the present invention can be obtained by firing a composition in which 02≦z≦0.012) by a conventional method.

The following is a description based on examples. PbO, MgO,
Raw materials of Nb2O5, TiO2, ZrO2, and CaF2 were weighed to have the composition shown in the table and mixed in a ball mill.

After filtering and drying it, it was calcined at 850° C. for 2 hours. After calcination, it was pulverized in a ball mill, molded, and then fired at 1250° C. for 45 minutes. The table shows the Kt when this sample was polarized at 100° C. and 5 KV/n for 30 minutes. Kt increases significantly by adding CaF2 compared to the case without addition. σ>1/3 for these samples
The range that satisfies the condition is 0.44≦y≦0.58. For samples with x − 0.025, 0.478≦
In the sample where y□0.618 and x□0.125,
It was confirmed through experiments that the conditions of 0.378≦y≦0.518 and σ>1/3 were satisfied. These σ>1
Within the range that satisfies the condition of /3, 0.002≦z≦0.01
With the addition of CaF2 in the range of
It was confirmed through experiments that the concentration reached 4%.

Claims (1)

[Claims] 1 (1-z[xPb(Mg1/3Nb2/3)O_3
+(1-x-y)PbTiO_3+yPbZrO_3]
In the composition formula of +zCaF_2, 0.025≦x≦0
．． 125, 0.372≦y≦0.618, 0.002≦
A piezoelectric ceramic composition characterized in that it has a road wall of z≦0.012.