Preparation parameters optimization and structure investigation of multiferroic bismuth ferrite

Multiferroic bismuth ferrite, BiFeO3 (BFO), was prepared using conventional solid state reaction method. The obtained powders were thermally treated at different temperatures (600-850 °C) and times (15 min-15 h) with two heating regimes (slow and fast) to investigate the optimum synthesis conditions. Rietveld refinement was applied to the X-ray diffraction data and Raman spectroscopy has been used to verify the phase purity. Both the temperature and time of the heat treatment were critical parameters to obtain the high BFO phase content. Sample of 95 wt% of BFO phase has been achieved by using fast heating/cooling regime of 30 min at 800 °C and leaching with HNO3 to eliminate the impurity phases Bi2Fe4O9 and Bi25FeO40. Upper and lower calcinations temperatures and times result in higher content of secondary phases. The Raman active modes confirmed the presence of the single phase of BFO. Additional physical measurement (electrical and magnetic) prove the multiferroic feature of BFO. The estimated high activation energy (0.89 eV) indicates the antiferromagnetic order. The magnetic hysteresis loops gives indication for the existence of a weak canting moment.