Abstract
Heating of the mixture of CaCO3, SnO2, SiO2 and Cr2O3 developed reddish color simultaneously with the formation of tin-sphene (CaO⋅SnO2⋅SiO2). Characterization of chromium in tin-sphene by chemical analysis, ESCA and ESR revealed that the chromium was mostly tetravalent. ESR and chemical analyses of vanadium in tin-sphene showed that the vanadium was also mostly tetravalent, substituting for the Sn4+ in the tetragonally distorted octahedral symmetry. It was pointed out that the only one broad absorption band in the visible region observed in the reflectance spectra of a chrome-tin pink stain would be caused by Cr4+ in this distorted octahedral symmetry. Furthermore, chemical states of chromium and tin in glazes containing calcium were studied by ESR and ESCA in connection with the glaze colors.
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