Compositional Fluctuation of PID(Zr_xTi_l-x)O₃ near Tetragonal-Rhombohedral Phase-Boundary

Abstract

Room temperature X-ray diffraction patterns of Pb (Zr_xTi_l-x)O₃ prepared by solid-state reaction showed the coexistence of tetragonal and rhombohedral phases in a composition near the morphotropic phase boundary. Above its Curie temperature (550°C), however, this material was distinctly of monophase in view of X-ray diffraction. These results are explained in terms of the occurrence of compositional fluctuation in this material, since “intrinsic PZT” has tetragonal-rhombohedral phase boundary at x=0.55 where the lattice constant changes drastically whereas such a discontinuity could not be observed in the high-temperature cubic region. The actual compositional fluctuation width, δx, was estimated by using the X-ray diffractometrically determined value of Δα/α together with lattice constant vs. x curve at 550°C. A room temperature X-ray diffraction profile of the tetragonal-rhombohedral coexisting specimen was simulated by a computer calculation on the assumption of the occurrence of compositional fluctuation and was compared with the observed profile.