Pressure-Squeezing Effect on the Phase Transition in Barium Titanate

Abstract

Pressure-squeezing effect on the ferro-paraelectric transition of barium titanate and a ceramic body was studied. The remarkable experimental results are as follows : (1) The pressure-sque-ezed barium titanate had a smaller heat of transition at the Curie temperature and a remarkable low dielectric constant which did not show a steep rise at the Curie temperature, 120°C. (2) The steep rise was not observed even when the pressure-squeezed sample had been annealed at 1200°C for 2 hr. (3) The pressure-squeezed sample showed no P-E hysteresis loop and had tetragonal symmetry characterized by broad peaks in X-ray patterns even above the Curie temperature.
It appears that the notable pressure-squeezing effects, i.e., decrease in grain size and formation of mechanical stresses among the crystal grains and of lattice defects, especially stacking faults, cause the hindrance to the displacement of ions and hence to the ferroelectric arrangement of spontaneous polarization.