Chemical state and distribution of Mn ions in Mn-doped α-Al2O3 solid solutions prepared in the absence and the presence of fluxes

We have investigated the oxidation state and localization of the Mn cations in the corundum lattice for Mn-doped α-alumina pigments prepared in the absence and the presence of fluxes by mainly using XPS, XANES and EXAFS techniques. It was found that irrespective of the preparation method, the pink colour of the pigments is mainly due to Mn(III) species dissolved in the corundum lattice, in which they form cluster containing ∼2 Mn cations. The more intense colour presented by the sample prepared in the presence of fluxes is due to the incorporation of a higher amount of Mn to the alumina lattice as a consequence of the presence of liquid phase which favours the diffusion process involved in the solid solution formation.