Synthesis of Bi25FeO39 by molten salts method and its mössbauer spectrum

A sample of Bi25FeO39 was synthesized by the molten salts method in 2 h at 750 °C with KCl-KBr as reaction media. The sample was characterized with X-ray powder diffraction and Mössbauer spectroscopy. The Rietveld refinement of the X-ray diffraction confirms that a sillenite type structure with a cell parameter a=10.190(4) Å was achieved, with only small traces of Bi2O3. In order to get a Mössbauer spectrum with a good signal to noise ratio, the synthesis was made using 95% enriched α-57Fe2O3. To our knowledge, this is the first time that a Mössbauer spectrum for the Bi25FeO39 has been recorded. The nonappearance of a magnetic sextet confirms its paramagnetic behavior. The measured Mössbauer parameters (IS=0.20±0.004 mm/s and QS=0.2±0.07 mm/s) correspond to Fe+3 in very symmetric surroundings, and rule out some interpretations given to the doublet observed in some Mössbauer spectra of BiFeO3.