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 Ca 10 Cr 6 −O 25 , Ca 3 Cr 2 O 8 , and Ca 5 Cr 3 O 12 , which form at temperatures >900°C at CaO:Cr 2 O 3 molar ratios of 3 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.