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 PbTiO 3 Pb 0.5 NbO 3 and PbTiO 3 ‐Pb o.5 TaO 3 . The ferro‐electric Curie temperature is lowered to 465OC. at the solubility limit (2 to 5% Nb or Ta). Replacement of Ti 4+ by Nb 5+ or Ta 5+ 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 δ less than 0.1 in the interval 25° to 525°C.