Determination of Valence States of Chromium in Calcium Chromates by Using X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

Calcium chromates with the empirical formulas Ca10Cr6−O25, Ca3Cr2O8, and Ca5Cr3O12, which form at temperatures >900°C at CaO:Cr2O3 molar ratios of geqslant R: gt-or-equal, slanted3 in an oxidation atmosphere have been synthesized in the pure state. X-ray absorption near-edge structure (XANES) spectroscopy has been used to determine the average valence state of chromium in the samples. The presence of unusual chromium valence states, 4+ and 5+, which was proposed via X-ray diffractometry studies, is strongly supported