Phase evaluation of Fe/Co pigments coated porcelain by rietveld refinement

Porcelain (white ware, celadon ware) coated with a ferrous sulfate and ferrous/cobalt sulfate was sintered at 1250 C. The specimens were investigated by HR-XRD, FE-SEM, HR-EDS, and UV-vis spectrophotometer. Through X-ray rietveld quantitative analysis, quartz and mullite were found to be the main phases for white ware, and mullite and plagioclase were found to be the main phases for celadon ware. When the pigment of ferrous/cobalt sulfate was applied, were identified as an andradite phase for celadon ware and a spinel phase for the white ware, and the amorphous phase, respectively. The L value, which was the brightness of the specimen, was 72.01, 60.92 for white ware and celadon ware, respectively. The ferrous and ferrous/cobalt pigment coated porcelain had L values of 44.89, 52.27 for white ware and celadon ware, respectively; with a values of 2.12, 1.40, and at b values of 1.45 and 13.79. As for the color of the specimens, it was found that the L value was greatly affected by the white ware, and the b value differed greatly depending on the clay. It was thought to be closely related to the production of the secondary phase such as Fe O and andradite phase produced in the surface layer.