The effects of sintering temperatures on dielectric, ferroelectric and electric field-induced strain of lead-free Bi_(0.5)(Na _(0.78)K_(0.22))_(0.5)TiO_3 piezoelectric ceramics synthesized by the sol-gel technique

摘要

Lead-free Bi_(0.5)(Na_(0.78)K_(0.22)) _(0.5)TiO_3 (BNKT) piezoelectric ceramics were synthesized by the sol-gel technique. The effects of sintering temperatures on the crystal structure, microstructure, densification, dielectric, ferroelectric and electric field-induced strain behaviors of the BNKT ceramics were investigated. X-ray diffraction patterns exhibited a pure perovskite structure from 1075 to 1150 °C. A scanning electron microscopy study revealed an increase in grain size with increasing sintering temperature. The density of the ceramics sintered at 1150 °C reaches a maximum value of 5.55 g/cm~3, which is 96% of the theoretical density. BNKT ceramics sintered at an optimum temperature of 1150 °C exhibited a high remnant polarization of 18.5 μC/cm~2, a high electric field-induced strain of 0.20% and dynamic piezoelectric coefficient d_(33) = (S_(max)/E_(max)) of 247 pm/V.