Mechanism of thermal decomposition of K₂FeO₄ and BaFeO₄: A review

This paper presents thermal decomposition of potassium ferrate(VI) (K₂FeO₄) and barium ferrate(VI) (BaFeO₄) in air and nitrogen atmosphere. Mössbauer spectroscopy and nuclear forward scattering (NFS) synchrotron radiation approaches are reviewed to advance understanding of electron-transfer processes involved in reduction of ferrate(VI) to Fe(III) phases. Direct evidences of Fe ^V and Fe ^IV as intermediate iron species using the applied techniques are given. Thermal decomposition of K₂FeO₄ involved Fe ^V, Fe ^IV, and K₃FeO₃ as intermediate species while BaFeO₃ (i.e. Fe ^IV) was the only intermediate species during the decomposition of BaFeO₄. Nature of ferrite species, formed as final Fe(III) species, of thermal decomposition of K₂FeO₄ and BaFeO₄ under different conditions are evaluated. Steps of the mechanisms of thermal decomposition of ferrate(VI), which reasonably explained experimental observations of applied approaches in conjunction with thermal and surface techniques, are summarized.