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

In current work, the effect of sintering atmospheres (N-2, air and O-2) on the structure, electrical properties, and defect mechanism of 0.8BiFeO(3)-0.2BaTiO(3) 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 N-2 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 N-2 sintered ceramics than that in O-2- and air sintered compositions. However, greatly reduced leakage currents were obtained in N-2 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 N-2 (2 h), which owned the optimal ferroelectric, piezoelectric, and electromechanical properties with piezoelectric constant d(33) = 98 pC/N, planar electromechanical coupling factors k(p) = 26.1 %, remnant polarization P-r = 25.7 mu C/cm(2), coercive field E-c = 74.6 kV/cm, and a high Curie temperature Tc = 632 degrees C, respectively.