Ceramic pigments and the European REACH legislation: Black Fe2O3?Cr2O3, a case study

Autores: Torre, A.G. de la; Aranda, M.A.G.; León-Reina, L.; Pérez, J.
Fuente: Int. j. app. ceram. technol.
8 (4), 905-910
2011

A Rietveld study for three ceramic pigments is presented. Two commercial black ceramic pigments, belonging to the (CrxFe1-x)2O3 family, are shown to be single crystalline phase with a negligible amorphous phase content. This conclusion is drawn from the existence of a unique crystalline phase and from the analysis of the values of the unit cell parameters. Furthermore, a much complex laboratory-prepared brown ceramic pigment has also been studied. This sample was synthesized by adding Al2O3 and MgO dopants in small quantities, below 3 wt percentage, to the previous system. The Rietveld analysis has shown the stabilization of two corundum structures with a compositions close to Cr0.50Fe1.50O3 and Al0.30Cr1.70O3, plus a spinel structure with composition close to MgCr2O4. An aluminum-rich amorphous oxide phase in low percentage is needed to balance the chemical analysis derived from the Rietveld study and that from XRF. Full mineralogical phase analyses of commercial pigments, plus the required solubility tests, may allow narrowing down of the number of toxicity tests required by REACH legislation by appropriate grouping of a set of ceramic pigments in representative compound(s). We anticipate that working in this direction may lead to significant savings in terms of costs and also in the required use of animals.