Experimental and Theoretical Investigations of Out-of-Plane Ordered Nanolaminate Transition Metal Borides: MCrSiB (M = Mo, W, Nb).

We report the synthesis of three out-of-plane chemically ordered quaternary transition metal borides (-MAB phases) of the chemical formula MCrSiB (M = Mo, W, Nb). The addition of these phases to the recently discovered -MAB phase TiMoSiB shows that this is indeed a new family of chemically ordered atomic laminates. Furthermore, our results expand the attainable chemistry of the traditional MSiB MAB phases to also include Cr. The crystal structure and chemical ordering of the produced materials were investigated using high-resolution scanning transmission electron microscopy and X-ray diffraction by applying Rietveld refinement. Additionally, calculations based on density functional theory were performed to investigate the Cr preference for occupying the minority 4 Wyckoff site, thereby inducing chemical order.