Answers are grounded in this paper and cite their sources.
Temperature variations of the refractive index on have been studied in single crystals of ferroelectric perovskites with diffuse phase transitions, with a different degree of ordering and also in the nonferroelectric crystals with pyrocphlore-type structure. Ferroelectric contribution δp to the index of refraction was obtained in ferroelectric perovskites. In all these compounds the temperature behaviour of δ(T) above Tc was found to vary in a same manner and this behaviour was interpreted in terms of local polarization in microregions with different transition temperatures. Contrary to that δ(T) around Tc behaves differently in ferroelectrics with diffuse phase transitions and in ferroelectrics with a different degree of ordering, that can be understood within the framework of percolation model.
No takes yet. Share an insight, caveat, or question.
Korshunov et al. (1992) studied this question.
Synapse has enriched 5 related papers. Consider them for comparative context: