A Thermodynamic Analysis of Ferroelectricity in Bismuth Titanate

Abstract

The elastic Gibbs function at zero stress has been derived for ferroelectric crystals with point symmetry 4/mmm in the paraelectric phase, and the possible ferroelectric states have been examined. For the special case of bismuth titanate, recent optical data are used to derive the absolute orientation and the temperature dependence of the polarization in the monoclinic ferroelectric state. The optical anisotropies are shown to be consistent with a simple temperature‐independent quadratic electro‐optic effect.