Neutron scattering studies of compositional heterogeneity in sol-gel processed lead zirconate titanates

Rietveld analyses of neutron diffraction data collected on a series of Pb(Zr0.5Ti0.5)O-3 samples, which had been prepared by sol-gel and conventional mixed oxide methods, showed that each sample contained both rhombohedral and tetragonal PZT (Pb[Zr1-xTix]O-3). The zirconium-to-titanium ratio in the two phases was found to be markedly different. Pair distribution functions were also calculated for some of the samples. The inability of a commonly used alkoxide-based sol-gel processing method to produce compositionally homogeneous samples is attributed to a compositional segregation that occurs early on during sol-gel processing and is not fully eliminated on high temperature heat treatment of the samples. A deliberate attempt to produce compositionally inhomogeneous materials, via the separate prehydrolysis of lead titanate and lead zirconate precursors, followed by mixing the resulting sols, was found to induce no more inhomogeneity than is present in materials prepared via the hydrolysis of precursors that were completely mixed.