Index of refraction in 'dirty' displacive ferroelectrics

We report measurements of the optic index of reflection as a function of temperature, n(T), for several highly disordered ferroelectrics: PLZT ceramic [Pb1-xLax(Zr0.65Ti0.35)1-x/4O3 where x = 0.08] and single crystals of Pb3(MNb2)O9 where M = Zn and Mg. The results are qualitatively different from the unusual displacive ferroelectric behavior and the difference is clearly due to local disorder. © 1973.