X-ray and phenomenological study of lanthanum-modified lead zirconate-titanates in the vicinity of the relaxor phase transition region

Abstract

X‐ray diffraction analyses of chemically derived Pb 1−x La x (Zr0.65Ti0.35)1−x/4O3 powders were combined with a phenomenological theory to investigate the corresponding single‐crystal thermodynamic properties of compositions approaching the relaxor ferroelectric phase transition region (x=0–0.04). The temperature dependence of the electrostrictive strain component, x 4, could be described by the Landau–Ginsburg–Devonshire phenomenological theory taking T c = 357 °C independent of La content (x). The single‐domain, single‐crystal elastic Gibbs free‐energy density was calculated as a function of temperature and composition. The calculated results were discussed in relation to a simple superparaelectric model of relaxor behavior involving the temperature stabilization of noninteracting polar microregions.