Effect of Two-Dimensional Pressure on the Permittivity of Fine- and Coarse-Grained Barium Titanate

The effect two-dimensional pressure on the permittivity of fine- and coarse-grained ceramic BaTiO₃ was investigated. It was shown that, unlike coarse-grained (10° or above) barium titanate, the permittivity of the fine-grained (1μ mean) material increased with the increase in two-dimensional compression perpendicular to the electrode, whereas for an intermediate grain size, the permittivity was almost independent of pressure. The apparent anomalous effect of the fine grain size on the pressure coefficient of permittivity was explained satisfactorily on the basis of an internal stress model using a modified Devon-shire thermodynamic treatment.