Composition variation and the monoclinic phase within Pb(ZrxTi1-x)O3 ceramics

High-resolution neutron powder diffraction data were collected from a Pb(Zr0.54Ti0.46)O-3 powder sample. Data were analysed using Rietveld refinement. The diffraction patterns showed the presence of two 'coexisting' phases, which had the rhombohedral R3c and monoclinic Cm symmetries at 4 K. A phase transformation between the R3c and Cm phases occurred as a function of temperature. The Bragg peaks of the Cm phase showed strongly reflection-indices-dependent line broadening due to the spatial variation of the Zr/Ti ratio, deltax. This was modelled using a microstrain broadening form developed by Stephens (1999 J. Appl. Crystallogr 32 281). Constant microstrain surfaces were plotted for each phase at different temperatures and the microscopic changes responsible for the observed changes were identified. The phase of Cm symmetry is reproducibly absent in the limit of deltax = 0.