Studies on lead titanate ceramics containing niobium or tantalum

Dielectric, lattice constant, and thermal-expansion measurements have been made on solid solution ceramics in the systems PbTiO3Pb0.5NbO3 and PbTiO3-Pb0.5TaO3. The ferro-electric Curie temperature is lowered to 465OC at the solubility limit (2 to 5% Nb or Ta). Replacement of Ti4+ by Nb5+ or Ta5+ in these perovskite-type solid solutions is accompanied by the creation of cation vacancies. These vacancies seem to facilitate material transport and aid sintering. Thus ceramics were obtained with up to 91% of theoretical density. These compositions have peak dielectric constants of the order of 10,000 with tan d less than 0.1 in the interval 25° to 525°C