Effect of Pressure on the Polarization Reversal in BaTiO₃

The maximum current i _m and the switching time t _s have been measured as functions of pressure p (\({\lesssim}2\) k bar) at room temperature in the field range: \(E{\lesssim}2\) k V/cm. The quantities i _m and 1/ t _s increase with hydrostatic pressure and decrease with two-dimensional pressure perpendicular to c -axis. The exponential laws: i _m = i _∞ e ^{-α/ E} and t _s = t _∞ e ^{α/ E} hold under every fixed pressure. The activation field α decreases linearly at the rate: (∂α/∂ p )/α=-5.0×10 ^-11 cgs with hydrostatic pressure, and increases linearly at the rate: (∂α/∂ p )/α=4.3×10 ^-11 cgs with two-dimensional pressure. These results agree qualitatively and quantitatively in the order of magnitude with the prediction of the Miller-Weinreich model. The pressure dependences of the 180° wall energy and the spontaneous polarization, which quantities have close relations with α, have been calculated by the molecular theory of Kinase and Takahasi, and fair agreement has been found between the theory and the experiment.