Doped oxides of cerium as inorganic colorants

Abstract

The colour of inorganic colorants is based on metal ions such as cadmium, lead, chromium or cobalt, the majority of which are unfortunately potentially toxic. Thus, there is in a need to introduce alternative metal or metal oxides, which would be environmentally friendly and economically viable as a replacement for potentially toxic inorganic colorants. Rare earth-based colorants offer an additional opportunity for the development of optically pure colours. In this study, a replacement for potentially toxic colorants has been sought through the use of a rare earth metal ion, cerium. Appropriate doping of cerium oxides with molybdenum and iron gives an orange-red colorant. The conditions ideal for optimal colour have been standardised and the resultant colorant characterised through powder X-ray diffraction techniques, particle size measurement, etc. The colorants exhibit good hiding power and tinting strength.