High Temperature X-Ray Diffraction Study of Sol-Gel Derived Pb(ZrxTi1-x)O3 Powders

The lattice parameters of sol-gel derived Pb(Zr x Ti 1-x )O 3 powders were determined as a function of temperature using a microcomputer automated Picker x-ray diffractometer. The spontaneous strain was calculated from the lattice parameters, and used with other experimental data to develop a thermodynamic phenomenological theory for the PZT solid solution system. A second tricritical point, where the transition changes front first to second order, was found to occur near or possibly at the morphotropic phase boundary between the tetragonal and high temperature rhombohedral phases. Using an equation derived from the theory, the spontaneous tilt angle of the oxygen octahedra in the low temperature rhombohedral phase was calculated from the experimental spontaneous strain data.