Preparation and Characterization of Multiferroics BiFeO_3

The multiferroic materials BiFeO3 nanopowders of dispersion uniformity were synthesized by the citric acid Sol-Gel method,using the iron(Ⅲ) nitrate and bismuth nitrate as the reactants and dilute nitric acid as the catalyst. The physical and chemical characteristics,such as structure,morphology and purity of BiFeO3 nanopowders were investigated by TG-DSC,XRD,FT-IR,SEM and AFM,respectively.The results indicate that the preparation and purity of BiFeO3 nanopowders have a profound influence on the precursor solution pH value of sol process and the calcined temperature of the xerogel.The optimum reaction conditions are the precursor solution pH=7–8 and calcined temperature of 600℃.It is found that BiFeO3 nanopowders with 100 nm in size,good dispersion and without Bi25FeO40 and Bi2Fe4O9 impurity phase are synthesized under the optimum reaction conditions.The saturation magnetization(Ms),the remanent magnetization(Mr) and the coercivity(Hc) of BiFeO3 nanopowders under the optimum reaction conditions are 1.08 A·m2/kg,0.13 A·m2/kg and 15.76 kA/m,respectively.