Greatly reduced leakage current and defect mechanism in atmosphere sintered BiFeO3–BaTiO3 high temperature piezoceramics

In current work, the effect of sintering atmospheres (N2, air and O2) on the structure, electrical properties, and defect mechanism of 0.8BiFeO3–0.2BaTiO3 lead-free piezoelectric ceramics has been investigated. X-ray diffractometer results indicated all the samples crystallized into the rhombohedrally distorted perovskite structure which was independent on the sintering atmospheres. Bi-containing impurity phases were observed in N2 sintered samples while not appearing in other atmospheres. X-ray photoelectron spectrum analysis indicated more Fe2+ ions, which can result in high leakage current, were involved in N2 sintered ceramics than that in O2- and air sintered compositions. However, greatly reduced leakage currents were obtained in N2 sintered ceramics which should be ascribed to the formation of secondary phases. The largest polarization and lowest leakage current were obtained in the sample sintered in N2 (2 h), which owned the optimal ferroelectric, piezoelectric, and electromechanical properties with piezoelectric constant d33 = 98 pC/N, planar electromechanical coupling factors kp = 26.1 %, remnant polarization Pr = 25.7 µC/cm2, coercive field Ec = 74.6 kV/cm, and a high Curie temperature Tc = 632 °C, respectively.