First principles studies on the impact of point defects on the phase stability of (AlxCr1-x)(2)O-3 solid solutions

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Publikace nespadá pod Filozofickou fakultu, ale pod Přírodovědeckou fakultu. Oficiální stránka publikace je na webu muni.cz.
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KOLLER C. M. KOUTNÁ Nikola RAMM J. KOLOZSVARI S. PAULITSCH J. HOLEC David MAYRHOFER P. H.

Rok publikování 2016
Druh Článek v odborném periodiku
Časopis / Zdroj AIP ADVANCES
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
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Doi http://dx.doi.org/10.1063/1.4941573
Klíčová slova THERMAL-STABILITY; 1ST-PRINCIPLES CALCULATIONS; ELECTRONIC-PROPERTIES; ARC EVAPORATION; FILM GROWTH; CORUNDUM; COATINGS; AL; SYSTEMS; MICROSTRUCTURE
Popis Density Functional Theory applying the generalised gradient approximation is used to study the phase stability of (AlxCr1-x)(2)O-3 solid solutions in the context of physical vapour deposition (PVD). Our results show that the energy of formation for the hexagonal a phase is lower than for the metastable cubic. and B1-like phases-independent of the Al content x. Even though this suggests higher stability of the a phase, its synthesis by physical vapour deposition is difficult for temperatures below 800 degrees C. Aluminium oxide and Al-rich oxides typically exhibit a multi-phased, cubic-dominated structure. Using a model system of (Al0.69Cr0.31)(2)O-3 which experimentally yields larger fractions of the desired hexagonal a phase, we show that point defects strongly influence the energetic relationships. Since defects and in particular point defects, are unavoidably present in PVD coatings, they are important factors and can strongly influence the stability regions. We explicitly show that defects with low formation energies (e.g. metal Frenkel pairs) are strongly preferred in the cubic phases, hence a reasonable factor contributing to the observed thermodynamically anomalous phase composition.
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