A novel cathodic arc evaporation process operated in pure oxygen forms corundum-type micro-crystalline structures at temperatures below 600°C. Thermally stable crystalline solid solutions of corundum-type (Al 1-xCrx)2Oy have been prepared with this method for x ≥ 0.3 at non-equilibrium conditions. The stability in (Al,Cr)2O3 phases can be explained by their degree of crystallinity and ordering within the structure. The applied processing method results in highly crystalline coatings of pure α-(Al1-xCr x)2Oy. With increasing fabrication temperature (maximum 600°), more stable phases are obtained showing no metal site splitting in the atomic structure. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA,.