Dielectric and Piezoelectric Properties of Niobium-modified BiInO₃–PbTiO₃ Perovskite Ceramics with High Curie Temperatures

Piezoelectric ceramics with T_C > 500 °C were projected in the perovskite BiInO₃–PbTiO₃ (BIPT) system based on their low tolerance factor (∼0.884). However, a stable perovskite phase could be synthesized only when the PbTiO₃ (PT) content was greater than 75%. Furthermore, the large tetragonality (c/a > 1.08) and low electrical resistivity made the ceramics difficult to pole. Niobium-modified BIPT ceramics with PT contents of 80% and 85% were found to possess significantly lower dielectric loss at elevated temperatures, making it possible to polarize the materials. Piezoelectric properties were measured for a BIPT85–1.5 mol% Nb composition with a Curie temperature of 542 °C; the longitudinal piezoelectric coefficient and coercive field were found to be 60 pC/N and 125 kV/cm, respectively.