Theoretical study of temperature dependence of spontaneous polarization, optical properties and free and clamped linear electrooptic coefficients of BaTiO3 in the tetragonal phase

The microscopic mechanism of refractive indices, birefringence, spontaneous polarization and free and clamped electrooptic effects of BaTiO3 is discussed by using a microscopic model taking account of a quantum method based upon the orbital approximation and the dipole-dipole interaction due to the local field acting on the constituent ions. It is found that the electronic polarizabilities play a major role in these calculations and that the birefringence delta n and the free and clamped linear electrooptic coefficients are in good agreement with the experimental data.