Structure and multiferroic properties of BiFeO_3 powders

摘要

Bismuth ferrite powders were synthesized by a simple sol-gel method at the temperature as low as 450 deg C. Single phase BiFeO_3 powders with a rhombohedral perovskite structure were fabricated after Bi-Fe gels were calcined at 450-650 deg C. Atomic ratio of Bi to Fe is approximately 1:1 for BiFeO_3 powders, as determined by energy dispersive X-ray spectrometer. BiFeO_3 powders show weak ferromagnetism at room temperature and strong size-dependent magnetic properties, which is different from the linear M-H relationship in BiFeO_3 ceramics. Dielectric anomaly at round 330 deg C near the magnetic transition point corresponds to the antiferromagnetic to paramagnetic phase transition, indicating the coupling between polarization and magnetization in BiFeO_3 powders. A reversible ferroelectric phase transformation of BiFeO_3 powders has been detected at 827 deg C by a differential thermal analysis.