Structure and multiferroic properties of BiFeO3 powders

Bismuth ferrite powders were synthesized by a simple sol–gel method at the temperature as low as 450 °C. Single phase BiFeO3 powders with a rhombohedral perovskite structure were fabricated after Bi–Fe gels were calcined at 450–650 °C. Atomic ratio of Bi to Fe is approximately 1:1 for BiFeO3 powders, as determined by energy dispersive X-ray spectrometer. BiFeO3 powders show weak ferromagnetism at room temperature and strong size-dependent magnetic properties, which is different from the linear M–H relationship in BiFeO3 ceramics. Dielectric anomaly at round 330 °C near the magnetic transition point corresponds to the antiferromagnetic to paramagnetic phase transition, indicating the coupling between polarization and magnetization in BiFeO3 powders. A reversible ferroelectric phase transformation of BiFeO3 powders has been detected at 827 °C by a differential thermal analysis.