Synthesis and characterization of Bi2Fe4O9 powders

Bi2Fe4O9 have been successfully prepared using ethylenediaminetetraacetic (EDTA) acid as a chelating agent and ethylene glycol as an esterification agent. Heating of a mixed solution of EDTA, ethylene glycol, and nitrates of iron and bismuth at 140 °C produced a transparent polymeric resin without any precipitation, which after pyrolysis at 250 °C was converted to a powder precursor for Bi2Fe4O9. The precursors were heated at 400–800 °C in air to obtain Bi2Fe4O9 powder and differential scanning calorimetry (DSC), thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterize the precursors and the derived oxide powders. XRD analysis showed that well-crystallized and single-phase Bi2Fe4O9 with orthorhombic symmetry was obtained at 700 °C for 2 h and BiFeO3 and Fe2O3/FeCO3 were intermediate phases before the formation of Bi2Fe4O9. Bi2Fe4O9 powders show weak ferromagnetism at room temperature.