Pressure-Induced Crossover from Long- to Short-Range Order in Compositionally Disordered Soft Mode Ferroelectrics

Results on a lanthanum-modified, lead zirconate-titanate have revealed (1) pressure-induced crossover from normal ferroelectric- (nFE-) to-relaxor (R) behavior; (2) the continuous evolution of the dynamics of the relaxation process; (3) a spontaneous R-to-nFE transition at a temperature well below the dynamic glass temperature of the R phase; and (4) the vanishing of this transition with pressure at a critical point. These results can be understood in terms of a large decrease in the correlation radius among polar nanodomains---a unique property of soft ferroelectric phonon mode systems.