Phase stability of Ti2AlC upon oxygen incorporation: A first-principles investigation
2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, Vol. 81, no 2, 024111-1-024111-8 p.Article in journal (Refereed) Published
The phase stability of Ti2AlC upon oxygen incorporation has been studied by means of first-principles calculations. Recent experimental observations of this so-called MAX phase (M = early transition metal, A = A-group element, and X = C or N) show that the characteristic nanolaminated structure is retained upon oxygen incorporation, with strong indications of O substituting for C. Therefore, a solid solution of C and O on the carbon sublattice has been simulated by the so-called special quasirandom structure method. Through a developed systematic approach, the enthalpy of formation of Ti2Al(C1−x,Ox) has been compared to all experimentally known competing phases, and has been found favorable for all C to O ratios at the composition of the MAX phase. A negative isostructural formation enthalpy has also been predicted for Ti2Al(C1−x,Ox). Altogether, the results indicate that a large amount of oxygen, at least up to x=0.75, might be present in the Ti2AlC MAX-phase structure without decomposition of the material into its competing phases. Furthermore, an effect of an increased oxygen content is a corresponding increase in the bulk modulus and a change in electronic properties. These results are of importance for further understanding and identification of possible composition range of the MAX-phase oxycarbide, and hence for the prospect of tuning the material properties by a varying incorporation of oxygen.
Place, publisher, year, edition, pages
2010. Vol. 81, no 2, 024111-1-024111-8 p.
IdentifiersURN: urn:nbn:se:liu:diva-53771DOI: 10.1103/PhysRevB.81.024111OAI: oai:DiVA.org:liu-53771DiVA: diva2:291770