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 BixFeyO1.5x+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.