Preparation and characterization of multiferroic BiFeO₃

The multiferroic materials BiFeO₃ nanoparticles 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 nanoparticles were investigated by thermogravimetry- differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), fourier transform infrared spectro- meter (FT-IR), scanning elecron microscope (SEM) and atomic force microscope (AFM), respectively. The results indicated that the preparation and purity of BiFeO₃ nanoparticles have a profound influence on the precursor solution pH value of sol process and the calcined temperature of the xerogel. The optimum reaction conditions were the precursor solution pH=7-8 and calcined temperature for 600. It is found that BiFeO₃ nanoparticles with 100nm in size, good dispersion and without Bi₂₅Fe₄O₉ and Bi₂Fe ₄O₉ impurity phase were synthesized under the optimum reaction conditions. At room temperature the saturation magnetization(Ms), the remanent magnetization(Mr) and the coercivity(Hc) of BiFeO₃ nanoparticles under the optimum reaction conditions are 1.08A·m ²·kg^-1, 0.13A·m²·kg ^-1 and 15.76kA·m^-1, respectively. The dielectric spectra shows that dielectric constant ε_r is 9.38 and dielectric loss tanδ is 0.04 in 10⁵ Hz.