Structure of sol-gel derived PbTiO3 dried lead titanate gel

The radial distribution function (g(r)) obtained from the Fourier transformation of x-ray diffraction intensities shows (g(r)) peaks at 2.11, 3.86, and 5.66 angstrom, corresponding to Ti-O and two Pb-Pb pairs. On the basis of this result, the structural model that fits the short range order prevailing in the sol-gel derived PbTiO3 is of a perovskite form of PbTiO3 and not the pyrochlore form observed in lead titanate glass quenched from the melt. These two materials, whether prepared by the sol-gel process or by melt quenching have the same glass transition and crystallisation temperatures but differ in their ferroelectric anomaly. The structural model derived in this study explains the ferroelectric anomaly for sol-gel derived lead titanates heat treated above 550-degrees-C, the temperature at which well developed perovskite crystals are grown. Quenched lead titanate glasses, which contain the pyrochlore form of lead titanate, do not exhibit a ferroelectric anomaly until heated above 900-degrees-C, the temperature at which the metastable pyrochlore phase is transformed to the perovskite phase which is responsible for the ferroelectric anomaly