Brown ceramic pigments based on chromium(III)-doped titanite obtained by spray pyrolysis

Cr-doped titanite (CaTiSiO5) pigments were synthesized through spray pyrolysis of aerosols generated from aqueous solutions containing colloidal silica, calcium chloride, titanium(IV) oxychloride and chromium(III) nitrate. This process yielded amorphous powders with spherical morphology and broad size distribution (<10 μm) after thermal decomposition at 600 °C. The titanite phase was obtained by further calcination at 800 °C without any addition of flux agents. The brown color of the pigments can be attributed mainly to the existence of Cr(IV) ions occupying both, octahedral positions of Ti(IV) and tetrahedral position of Si(IV), together with a small amount of Cr(III) present as Cr2O3. The optimum pigment obtained by this method corresponded to a Cr/titanite mole ratio of 0.04.