Peculiarities of heating-induced transformations in Fe(III) β-oxyhydroxides

Abstract

Recent interest in chemically synthesized iron β-oxyhydroxides and their calcination products should be linked with application of these materials in Li+ batteries, fuel and solar cells, bio sensing, etc. In this study, transformations of fluoride and chloride stabilized Fe(III) β-oxyhydroxides upon heating at temperatures up to 1000 °C were analyzed with a view to increase knowledge about predictable calcination of these compounds. Morphological and structural transformations were studied using various techniques such as X-ray powder diffraction, X-ray photoelectron spectroscopy, thermogravimetry, differential thermal analysis, Mössbauer spectroscopy and energy-dispersive X-ray spectroscopy analysis. Our findings revealed significant differences in the decomposition behavior of β-FeOOH,F and β-FeOOH,Cl. It was concluded that thermal decomposition of β-FeOOH,F proceeds through the formation of intermediate states with increasing relative amount of fluoride, resulting eventually in the composition close to nonstoichiometric FeOF.