Ceramic pigments in the ternary pseudosystem ZnO·Al2O3-ZnO·Fe2O3-ZnO·Cr2O3$ /

Six pigments were prepared with a composition located inside the ternary pseudosystem ZnO·Al2O3-ZnO·Fe2O3-ZnO·Cr2O3$ /. These samples were thermally treated at 1300 °C. The pigment structure was established by X-ray diffraction as solid solution of the spinel type. The valence of the chromophore and the co-ordination number of the cations were assigned by EPR spectra. 5 mass-% of each pigment was embedded in a glaze with the melting temperature of 1180 °C without opacifier. The objective characterization of the coloured glaze was performed by diffuse reflectance spectra registered in the 250-2000 nm domain. There was evidence of both d-d and charge transfer bands for Fe$+3+ and Cr3+ species; the latter bands making the dominant contribution to the colour which ranged from orange to reddish-brown and dark brown.