HF2EPR spectroscopy of Fe(III) impurities in a blue hercynite-based pigment

The presence of corundum was found to remove ferric iron, eventually formed during the synthesis, from hercynite. The dilution of Fe(III) in the Al2O3 phase results in a quenching of its coloring effects. As a consequence, corundum acts as a buffer during the synthesis, stabilizing the pigment chromatic yield.