抄録
The effects of the following three kinds of mechanical pressures upon the dielectric properties of barium-strontium titanate ceramics have been investigated: (1) hydrostatic pressure, (2) compression parallel to the electrode surface and (3) compression normal to the electrode surface (as shown in Fig. 1). Especially the influences of these pressures on the Curie point and on the permittivity in the cubic region have been investigated.
With increasing hydrostatic pressure, Curie point of (Ba 75-Sr 25) TiO3 is reduced with a slope of 6.0 (±0.5)×10−3 degree·cm2/kg, and its permittivity vs. temperature curve is shifted to lower temperatures; these results are in good agreement with those of BaTiO3 single crystals, recently published by Merz. The Curie point of this sample is raised by the two kinds of compressions. On the other hand, permittivity is lowered in all temperature range by normal compression, but by parallel compression permittivity vs. temperature curve is shifted to higher temperatures. The effect of normal compression is in good agreement with the one investigated by Takagi, Sawaguchi and Akioka about BaTiO3 ceramics.
In the cubic region, the variation of the permittivity by these pressures can be interpreted by the phenomenological theory presented by Devonshire, and the coefficients g11 and g12, which were introduced in his theory, can be calculated using the results of our experiments. In addition, using cathode ray oscillograms measurements have been made on the effects of pressures on the polarization, and the results are consistent with the data of the permittivity measurements.
