In situ synthesis of orange rutile ceramic pigments by non-conventional methods

Different precursor-mixtures of orange Cr,Sb-TiO₂ ceramic pigment have been obtained by non-conventional methods (heterogeneous ammonia coprecipitation, urea homogeneous coprecipitation, PECHINI polyester method and an original aqueous–organic coprecipitation method in water–diethylenglycol medium) in order to produce in situ the pigment through the ceramic body firing. The pigmenting performances of powders were appraised in two cases: (a) as ceramic pigment for glazed porcelain stoneware and (b) as ceramic inks for screen printing of porcelain stoneware. Samples were characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV–vis-NIR spectroscopy by diffuse reflectance method, CIE-L*a*b* colour parameters, BET specific surface area and crystallite size measured by the Scherrer method. The colouring performance of raw powders obtained by non-conventional methods in glazed porcelain stoneware improves that of the ceramic samples fired at 1100 °C used as reference. TEM observations indicate nanostructured powders with pigmenting performance depending on factors such as their specific surface area (BET), the crystalline phases detected by XRD (e.g. anatase–rutile presence) and their crystallite size (Scherrer measurements). Ammonia coprecipitated samples, both in water and in water–diethylenglycol medium without surfactant addition, or modified by the addition of sodium dodecyl sulphate as surfactant, stand out by their colouring performance.