Evidence of monoclinic phase and its variation with temperature at morphotropic phase boundary of PLZT ceramics

Abstract

(Pb0.92La0.08)(Zr0.60Ti0.40)O3 referred to hereinafter as PLZT 8/60/40 ceramics, near the morphotropic phase boundary region, show the ultra-high piezoelectric properties. Several attempts have been made and the said properties were related with processing (The combinatorial approach of mechanical activation and cold isostatic pressing), density, microstructure and MPB, however, still more clarification is required. In this study, more detailed and elaborated structural analysis was done for PLZT 8/60/40 ceramics. Slow scan X-ray diffraction data were collected from room temperature to elevated temperature and analysed by Rietveld refinement method, which confirms the coexistence of two phases at MPB, instead of the previously reported single tetragonal phase. These two phases have the tetragonal (P4mm) and monoclinic (Cm) symmetries. This monoclinic phase was supposed to be responsible for the origin of ultra-high piezoelectric properties in PLZT 8/60/40 ceramics. The changes in both phases were also studied as a function of temperature.