Room temperature structure of Pb(Zr_xTi_1-xO₃) around the morphotropic phase boundary region: a rietveld study

Abstract

We have carried out a detailed Rietveld analysis of x-ray powder diffraction data of Pb(Zr_xTi_1-x)O₃ (PZT) compositions across the morphotropic phase boundary (MPB) region (x=0.515, 0.520, 0.525, 0.530). It is shown that the structure of PZT is pure tetragonal for x≤0.515 with space group P4mm. In the MPB region, 0.515<x<0.530, the tetragonal and monoclinic (space group: Cm) phases are found to coexist as a result of a first order phase transition between the low temperature monoclinic and high temperature tetragonal phases. Further, arguments are advanced to show that the hitherto believed rhombohedral structure (F_R^HT) of PZT for 0.530≤x≤0.62 is more likely to be monoclinic.