Benefits of oxygen incorporation in atomic laminates. (4th March 2016)

• Record Type: Journal Article
• Authors: Dahlqvist, Martin
• Is Part Of: Journal of physics. Volume 28:Number 13(2016)
• Publication Date: 2016-03-04
• Subjects: atomic laminate -- Cr2AlC -- Ti2AlC -- first-principles calculations -- electronic structure -- charge transfer -- Bader analysis; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/0953-8984/28/13/135501
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: Atomic laminates such as MAX phases benefit from the addition of oxygen in many ways, from the formation of a protective oxide surface layer with self-healing capabilities when cracks form to the tuning of anisotropic conductivity. In this paper oxygen incorporation and vacancy formation in M 2 AlC ( M = Ti, V, Cr) MAX phases have been studied using first-principles calculations where the focus is on phase stability and electronic structure for different oxygen and/or vacancy configurations. Oxygen prefers different lattice sites depending on M -element and this can be correlated to the number of available non-bonding M d -electrons. In Ti2 AlC, oxygen substitutes carbon while in Cr2 AlC it is located interstitially within the Al-layer. I predict that oxygen incorporation in Ti2 AlC stabilizes the material, which explains the experimentally observed 12.5 at% oxygen ( x = 0.5) in Ti2 Al(C1− x O x ). In addition, it is also possible to use oxygen to stabilize the hypothetical Zr2 AlC and Hf2 AlC. Hence, oxygen incorporation may be beneficial in many ways. Not only can it make a material more stable, but it also can act as a reservoir for internal self-healing with shorter diffusion paths.