Synthesis of Cr-doped CaTiSiO5 pigments by spray drying

Cr-doped CaTiSiO5 were synthesized by spray drying of an aqueous solution of precursor salts plus further calcining the resulting powders. The samples were prepared by conventional ceramic method as well for comparison study as ceramic pigments. The evolution of the present crystalline phases with applied thermal treatments has been studied by X-Ray Powder Diffraction (XRPD) and thermal analysis (DTA/TG). The powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction. The color efficiency of pigments was evaluated by colorimetric analysis (CIE Lab system). Results showed clearly efficiency of the spray dried procedure compared with the solid state reaction process. The produced powders consisted spherical particles with brad size distribution (3µm), developing typical brown color. UV-VIS-NIR spectroscopy reveals the existence of Cr(III) as a majority phase occupies basically octahedral sites substituting Ti(IV), which must be responsible for the brown color of this pigment. Furthermore, Cr(IV) ions were found in octahedral coordination substituting Ti(IV) and small amount of tetravalent chromium substitutes for tetrahedral Si(IV).