Syntheses of Fe2O3/silica red inorganic inclusion pigments for ceramic applications

The work focuses on the syntheses of red inorganic ceramic pigments by inclusion of hematite in a fumed silica matrix. Leaching tests in boiling solutions of concentrated (36 wt%) hydrochloric acid demonstrated that, starting from mixtures of fumed silica and synthetic goethite, the occlusion of hematite occurs by calcination at 1150-1200 degrees C for 2-4 h. Better results were obtained by using fumed silica having surface area ranging from 300 to 400 m(2)/g. A continuos change in colour was measured by comparing L-a-b values of the calcined samples and more information were obtained by the Kubelka-Munk absorption function. Because its chemical and thermal stability, the obtained heteromorphic pigment may be considered a suitable red pigment for ceramic manufacturing by fast firing cycles.