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V. Dalbauer, J. Ramm, S. Kolozsvári, C.M. Koller, P.H. Mayrhofer:
"Phase formation and oxidation behaviour of cathodic arc evaporated Al_xCr_1-x and Al_xCr_1-xOδ thin films";
Poster: EMRS Spring Meeting 2017, Straßburg; 2017-05-22 - 2017-05-26.

Aluminium oxide is highly valued for many applications due to its exceptional thermo-chemical properties and exhibits - in case of the thermodynamically stable corundum (α) structure - also a high hardness and adequate wear resistance. At deposition temperatures lower than 800 °C, transient oxides, as for instance the γ-Al2O3 phase, are more likely to crystallize during vapour deposition.
Even though considerable progress has been made in the last years by the synthesis of (Al,Cr)2O3 solid solutions with corundum-like properties, the deposition of single-phased α-Al2O3 coatings at lower temperatures via physical vapour deposition still poses a great challenge and thus demands further investigations. With the objective to shed further light on the formation of (Al,Cr)2O3, we investigated the structural evolution of intermetallic Al1-xCrx and substoichiometric Al1-xCrxOδ films (with x = 0.1, 0.25, 0.3, 0.50, 0.75), deposited by cathodic arc evaporation, and their oxidation behaviour.
The phase composition of our coatings is dominated by Al13Cr2, Al8Cr5, or
AlCr2 next to Al and Cr. At low oxygen flow rates during the deposition, the oxide formation proceeds via a distinct refinement of the initially pronounced columnar microstructure. We can show that both, the Al/Cr-ratio as well as the oxygen content of the coatings and their morphology significantly influence the scale formation during post deposition oxidation at temperatures between 900 and 1050 °C.

Project Head Paul Heinz Mayrhofer:
Christian Doppler Labors für anwendungsorientierte Schichtentwicklung