Thermal decomposition of barium ferrate(VI): Mechanism and formation of FeIV intermediate and nanocrystalline Fe2O3 and ferrite

Simple high-valent iron-oxo species, ferrate(VI) ((FeO42-)-O-VI, Fe(VI)) has applications in energy storage, organic synthesis, and water purification. Of the various salts of Fe(VI), barium ferrate(VI) (BaFeO4) has also a great potential as a battery material. This paper presents the thermal decomposition of BaFeO4 in static air and nitrogen atmosphere, monitored by combination of thermal analysis, Mossbauer spectroscopy, X-ray powder diffraction, and electron-microscopic techniques. The formation of Fe-IV species in the form of BaFeO3 was found to be the primary decomposition product of BaFeO4 at temperature around 190 degrees C under both studied atmospheres. BaFeO3 was unstable in air reacting with CO2 to form barium carbonate and speromagnetic amorphous iron(III) oxide nanoparticles (<5 nm). Above 600 degrees C, a solid state reaction between BaCO3 and Fe2O3 occurred, leading to the formation of barium ferrite nanoparticles, BaFe2O4 (20-100 nm). (C) 2016 Elsevier B.V. All rights reserved.