Effect of synthesis conditions on the structure of PbTiO3

The phase composition of PbTiO3 samples prepared from PbO + TiO2 and PbO + TiO2 · H2O mixtures is determined. The effect of mechanical stress on the structure of PbTiO3 prepared by high-temperature firing of a PbO + TiO2 mixture is investigated experimentally. It is shown that low-temperature synthesis yields not only the perovskite phase of PbTiO3 but also an oxygen-deficient pyrochlore phase with an increased lattice parameter. With increasing temperature, the content of the latter phase drops to zero. The pyrochlore-perovskite phase transition in PbTiO3 is discussed in terms of crystal chemistry and close packing of atoms.