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
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