Investigations of Feldspar-Quartz Raw Materials After Firing: Effect of Various Na2O/K2O Ratio and Synthetic Pigments Addition

摘要: Different techniques (chemical analysis, X-ray diffraction, Mossbauer spectroscopy, UV-Vis-NIR spectrophotometry and chromaticity measurements) were used to study the color variation of feldspathic raw materials after firing at 1200 °C. Two varieties feldspar-quartz grits (with Na2O or K2O prevalence) doped with synthetic pigments (hematite rutile) heat-treated in an oxidizing atmosphere. The results obtained indicate that ceramic body may not only depend on presence analytical content coloring elements (such as iron titanium), but their valence state chemical characteristics melt itself. prevalence larger alkali K+ ions over Na+ cause reduction coordination number iron. This has a significant effect length Fe–O bond, which turn influences capacity for light absorption specific wavelength. spectrophotometric measurements showed pronounced disparity between samples oxides. introduction caused clear changes spectral dependence total absorbance. absorbance increased whole measuring range, particular visible part spectrum. Furthermore, red-shift bands towards longer wavelengths attributed oxygen-metal charge transfer (OMCT) interactions Fe3+ O2− well d-d transitions within was observed.