Abstract

BaTiO₃ [1] and KNbO₃ [2] are among the most intensively studied photorefractive materials. Both BaTiO₃ and KNbO₃ are cubic perovskites at their respective growth temperatures and undergo the same sequence of cubic-tetragonal-orthorhombic-rhombohedral phase transitions upon cooling. The phase transitions occur at 132, 10 and −90 °C for BaTiO₃ and at 435, 223 and −50 °C for KNbO₃. At room temperature, tetragonal BaTiO₃ and orthorhombic KNbO₃ are both ferroelectric with 6 and 12 possible orientations for the spontaneous polarization, respectively.

© 1987 Optical Society of America