Phase homogeneity in Nd-doped lead titanate ceramics

A series of Nd-doped lead titanate ceramics were prepared by solid state reaction. The constituent oxides were mixed, calcined at temperatures between 400°C and 1100°C, and subsequently sintered at 1300°C. Analysis of the calcined powder indicated the formation of a crystalline tetragonal perovskite phase with lattice parameters approaching those of pure lead titanate, even for Nd contents up to 16 at%. In contrast, the sintered ceramics exhibited a continuous reduction in the c/a ratio with increasing Nd content. It was concluded that this was due to compositional inhomogeneity, i.e. that the Nd was present as an amorphous or poorly crystalline intermediate reaction product in the powders calcined at temperatures of 1100°C or less, whereas in the sintered ceramics a true lead-neodymium titanate solid solution had been formed.