Mierostmcture, ferroelectric and piezoelectric properties of Bi_(0.5)K_(0.5)TiO_3-modified BiFeO3-BaTiO_3 lead-free ceramics with high Curie temperature

摘要

The effects of composition, sintering temperature and dwell time on the microstructure and electrical properties of (0.75-A)BiFeO_3-0.25BaTiO_3-xBi_(o.5)K_(o.5)TiO_3 + lmol% MnO_2 ceramics were studied. The ceramics sintered at 1000 °C for 2h possess a pure perovskite structure and a morphotropic phase boundary of rhombohedral and pseudocubic phases is formed at x=0.025. The addition of Bi_(0.5)K_(0.5)TiO_3 retards the grain growth and induces two dielectric anomalies at high temperatures (T_1~ 450-550 °C and T_2 ~ 700 °C, respectively). Alier the addition of 2.5mol% Bi_(0.5)K_(0.5)TiO_3, the ferroelectric and piezoelectric properties of the ceramics are improved and very high Curie temperature of 708 °C is obtained. Sintering temperature has an important influence on the microstructure and electrical properties of the ceramics. Critical sintering temperature is 970 °C. For the ceramic with x=0.025 sintered at/above 970 °C, large grains, good densiflcation, high resistivity andl snhanced electrical properties are obtained. The weak dependences of microstructure and electrical properties on dwell time are observed for the ceramic withx=0.025.