Iron antimonate

Abstract

Iron antimonate, prepared by the calcination of precipitates at elevated temperatures, has been examined by X-ray powder diffraction, ⁵⁷Fe and ¹²¹Sb Mössbauer spectroscopy, energy dispersive X-ray microanalysis, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The nature of iron antimonate is critically dependent on the environment in which the dried precipitate is calcined. Although iron antimonate prepared from iron-rich reaction mixtures is formed in the presence of α-Fe₂O₃, the iron antimonate prepared by the calcination of equimolar mixtures of iron and antimony and of antimony-rich reactants in air where the excess antimony oxide can volatilise is formed as a rutile-related solid containing iron(III) and antimony(V). Iron antimonate prepared by calcination of antimony-rich reactant mixtures in evacuated sealed silica tubes is covered by a layer of antimony oxide which can be removed by treatment with hydrochloric acid. The rutile-related iron antimonate prepared under these conditions contains iron(III), iron(II), antimony(V), and antimony(III) with the iron(II) species being accommodated in both lattice and surface sites.