Thermodynamic point defect model of barium titanate and application to the photorefractive effect

We present a model that provides a means for understanding the effects of crystal growth and processing conditions on the photorefractive properties of BaTiO3. The densities of photorefractive centers are calculated from a thermodynamic point defect model. This model allows for the existence of transition-metal dopants in multiple valence states and for the incorporation of more than one species with levels in the band gap. Beam-coupling gain and response time are calculated as a function of temperature and oxygen partial pressure of treatment for various dopant types and concentrations. The predicted behavior is compared with existing experimental data on BaTiO3 crystals, and implications for improving the photorefractive performance are discussed.