Synthesis by pyrolysis of aerosols and ceramic application of Cr-doped CaYAlO4 red–orange pigments

The synthesis of red–orange Cr-doped YCaAlO4 pigments has been improved (softer thermal conditions and lower environmental impact) and optimised by using the pyrolysis of aerosols method. We also study the crystallochemical features of the Cr chromophore with special emphasis on its oxidation state which has not been yet clarified, finding that Cr(III) and Cr(IV) species are present in the octahedral and interstitial tetrahedral sites of the YCaAlO4 lattice, respectively. Finally, the applicability of this system as ceramic pigment was tested using conventional industrial glazes. A change from orange to pink shades was detected after glaze firing, which is mainly attributed to the Cr3+ to Cr4+ oxidation.