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A Kirnbauer, C. Koller, S. Kolozsvári, P.H. Mayrhofer:
"Multielement rutile-structured AlCrNbTaTi-oxide coatings synthesised by reactive magnetron sputtering";
Poster: 46th International Conference on Metallurgical Coatings and Thin Films, San Diego; 2019-05-19 - 2019-05-24.

A new alloying concept gained tremendous attraction in the field of materials research within the last years-so-called high-entropy alloys. These are defined as alloys with a configurational entropy of at least 1.5 R (R being the universal gas constant). To reach this specific value, the alloy ought to consist of at least 5 elements in a compositional range between 10 and 30 at.%. This concept may also be transferred to ceramic-based materials, in which the respective constituents are binary ceramics borides, carbides, nitrides, or oxides-the latter of which are subject to the present study.
AlCrNbTaTi-oxide coatings were prepared by reactive magnetron sputtering in a lab-scaled deposition system using a single powder-metallurgically produced compound target (composition AlCrNbTaTi 20/20/20/20/20 at.%). Systematic variations of the O2/Ar-ratio used for the deposition of these high-entropy films to determine basic structure-property-relationships.
The coatings crystallise partly in a single-phased rutile structure, are slightly enriched in Ta and exhibit nearly a MeO2 stoichiometry with an oxygen content of ~64 at.%. The indentation hardness of ~20 GPa in the as-deposited state is for some of the coatings slightly higher than compared to binary or ternary oxides. The thermal stability was investigated by vaccum annealing treatments with subsequent XRD and indentation measurements to gain information about the evolution of the structure and the mechanical properties.
Our results clearly show that a high-entropy concept applied to oxide thin films using a single powder-metallurgically-produced compound target is a promising strategy in promoting single-phased and mechanically/thermally- stable AlCrNbTaTi oxide coatings.