Cr-doped titanite pigment based on industrial rejects

This work reports the development of inorganic pigments based on chromium doped titanite (CaTiSiO5). For economical and environmental reasons, wastes were used as raw materials but similar formulations from pure reagents were also prepared to assess the effect of impurities contained in wastes. Pigments were characterised by XRD, SEM + EDS microprobe analysis, and UV–vis–NIR spectroscopy. The colouring mechanism (the pigment is reddish brown) seems to result from the combined contribution of octahedral Cr(III) and tetrahedral Cr(IV) species replacing Ti4+ and Si4+, respectively. In both pure reagents and waste-based pigments, colorimetric parameters were evaluated and their colouring performance was tested in transparent and opaque ceramic glazes. Intense and stable brown hues were developed with optimized formulations, i.e. containing 0.044Cr at 1300 °C.