Oxygen incorporation and defect formation in Ti2AlC, V2AlC and Cr2AlC from first-principles calculations
2014 (English)Manuscript (preprint) (Other academic)
We have studied oxygen incorporation and defect formation in M2AlC (M = Ti, V, Cr) MAX phases using first principles calculations. Evaluating phase stability and electronic structure for different oxygen and/or vacancy configurations, we show that oxygen prefer different lattice sites depending on M-element, which can be correlated to the number of available non-bonding M d-electrons. The results show that oxygen substitutes for carbon in Ti2AlC, while forming an interstitial oxygen in the Al-layer for Cr2AlC. We also predict that oxygen incorporation in Ti2AlC stabilizes the material, which explains the experimentally observed 12.5 at% oxygen (x = 0.5) in Ti2Al(C1-xOx). Due to similar valence electron configuration of Ti2AlC and the hypothetical M2AlC (M =Zr, Hf), we also investigate if oxygen can be used to stabilize the latter MAX phases.
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IdentifiersURN: urn:nbn:se:liu:diva-104758OAI: oai:DiVA.org:liu-104758DiVA: diva2:698829