Co speciation in blue decorations of blue-and-white porcelains from Jingdezhen kiln by using XAFS spectroscopy

Co K-edge XAFS measurements were carried out to characterize the oxidation state and chemical environment of cobalt element in the blue decorations of blue-and-white porcelains manufactured by Jingdezhen official kiln during Yuan and Ming dynasties with the aim to investigate its coloring mechanism. XANES spectra showed that cobalt was present as both divalent and trivalent ions and the ratios of Co2+/Co3+ were almost similar for all samples with different historical periods. EXAFS analysis indicated that cobalt atom was situated in both octahedral and tetrahedral sites. Considering the empirical optical absorption in visible region, it was assumed that divalent ions located at tetrahedral sites made the main contribution to the blue color.