Theoretical and Experimental Exploration of a Novel In-Plane Chemically Ordered (Cr2/3M1/3)2AlC i‑MAX Phase with M = Sc and Y

• Published in: Crystal growth & design 2017-11, Vol.17 (11), p.5704-5711
• Main Authors: Lu, J, Thore, A, Meshkian, R, Tao, Q, Hultman, L, Rosen, J
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.7b00642

We have uncovered two inherently laminated transition metal carbides, (Cr2/3Sc1/3)2AlC and (Cr2/3Y1/3)2AlC, which display in-plane chemical order in the carbide sheet and a Kagomé pattern in the Al layer. The phases belong to the most recently discovered family of so-called i-MAX phases. The materials were synthesized and the crystal structures were evaluated by means of analytical high resolution scanning transmission electron microscopy, selected area electron diffraction, and X-ray diffraction Rietveld refinement. An orthorhombic structure of space group Cmcm (#63) and a monoclinic structure of space group C2/c (#15) are solved. The compounds were investigated by first-principles calculations based on density functional theory, suggesting close to degenerate anti-ferro- and ferromagnetic spin states, dynamical and mechanical stability, and a Voigt bulk modulus in the range 134–152 GPa.