Preparation and multi-properties of insulated single-phase BiFeO3 ceramics

Six types of BiFeO₃ ceramic samples, with subtle differences in synthesis conditions, were prepared. The comparison of their phases, electrical resistivity, and porosity revealed that the use of Bi₂O₃ and Fe₂O₃ powders of <1 μm size and a rapid liquid-phase sintering process of 855 °C for 5 min at 100 °C/s is beneficial to synthesize poreless single-phase BiFeO₃ samples with high electrical resistivity of ∼5×10¹² Ω cm. Deoxygenated Bi_xFe_yO_{1.5x+1.5y−δ} (x≠y, δ≥0) impurities were identified and found to be the main cause of low electrical resistivity and high porosity in the multi-phase samples. Large saturation polarization of 16.6 μC/cm² and low leakage current density of 30 mA/m², both at a high electric field of 145 kV/cm, were measured in the optimized single-phase samples at room temperature besides a large piezoelectric d₃₃ coefficient of 27 pC/N and an obvious canted antiferromagnetic behavior.