Pressure as a probe of the glassy properties of compositionally disordered soft mode ferroelectrics: (Pb0.82La0.12)(Zr0.40Ti0.60)O3 (PLZT 12/40/60)

Abstract

It is shown that hydrostatic pressure qualitatively changes the dielectric response of a lanthanum-modified, lead zirconate–titanate (PLZT 12/40/60). At 1 bar this material exhibits, on cooling, a very weak relaxor (R) response followed by a spontaneous R-to-normal ferroelectric (nFE) transition. Pressure induces crossover to full relaxor behavior and reveals the continuous evolution of the dynamics and energetics of the relaxation process. These results, which are similar to our earlier results on other disordered perovskites, appear to be general features of soft mode ferroelectrics with random site dipolar impurities or polar nanodomains. They can be understood in terms of a large decrease with pressure in the correlation radius among polar nanodomains—a unique property of soft ferroelectric mode systems. An analogy between the influences of increasing pressure and increasing La concentration on the dielectric response of PLZTs is demonstrated, but it is the pressure results that clarify the physics.