Ferroelectric properties of BiFeO3 ceramics sintered under low oxygen partial pressure

BiFeO3 ceramics were prepared in various atmospheres with hydrothermally-synthesized BiFeO3 crystalline powders, and their dielectric and ferroelectric properties were investigated. The single BiFeO3 phase was formed when the sample was sintered at 800 .deg. C under air, and a minor Bi2Fe4O9 phase was observed when it was sintered under a N2 or an Ar atmosphere. The BiFeO3 ceramic sintered under N2 showed a dense microstructure and superior electric properties: a dielectric constant of 75, a low loss tangent of 0.01 at 100 kHz and a high resistivity of 1.37 x 1011 Ω · cm. A pinched and asymmetric P-E hysteresis and a typical butterfly-shaped S-E loop were observed in the BiFeO3 ceramic sintered under N2. The electric properties of BiFeO3 ceramics sintered in various atmospheres are discussed on the basis of defect chemistry.