Crystalline ferroelectrics with glassy polarization behavior

Abstract

We report measurements of the optic index of refraction as a function of temperature, $n \mathrm{}\left(T\right)\mathrm{}$, in the crystalline ferroelectrics having the simple perovskite ($\mathrm{AB}{\mathrm{O}}_3$) structure. We show that these crystals possess a local, randomly oriented, nonreversible polarization below a temperature $T_d$ several hundred degrees above the ferroelectric phase-transition temperature $T_c$. Using a simple model, we account for this behavior and understand quantitatively the values of $T_d$. This model, we believe, contains the basic physical understanding of ferroelectrics with a diffuse phase transition.