Elastooptic Effect in BaTiO3

Abstract

The temperature dependence of the elastooptic coefficient in BaTiO3 is theoretically and experimentally investigated in the vicinity of the cubic-tetragonal phase transition point (∼113°C). A theory of the elastooptic effect in BaTiO3 is developed through the anharmonic potential method. It is shown that nonlinear coupling among the electronic polarization, strain and soft phonon causes the temperature dependence of the elastooptic coefficient. The elastooptic coefficient p11 of a poled BaTiO3 single crystal is measured by the Dixon-Cohen method as a function of temperature near the phase transition point. In the tetragonal phase, p11 is almost temperature-independent, whereas in the cubic phase, p11 is strongly dependent on temperature. The above theory accounts for these experimental results.