Exploration of Cation Substitution in the Layered Compound CrWN 2
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Exploration of Cation Substitution in the Layered Compound CrWN2 K. Scott Weil,1 Prashant N. Kumta,2 and Jekabs Grins3 Department of Materials Science, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A. 2 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 99352, U.S.A. 3 Department of Inorganic Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden 1
ABSTRACT A series of derivative compounds based on the layered parent phase CrWN2 have been synthesized using a complexed precursor synthesis route. X-ray diffraction analyses demonstrate that both the chromium and tungsten display mutual substitution for one another and can also undergo considerable extensive replacement by a wide variety of cation species without significantly altering the original layered structure of the parent dinitride compound. The precursor approach employed here appears to offer a ready technique for exploring compositional phase space in layered nitrides of this type.
INTRODUCTION Inorganic compounds that crystallize in layered structures are of scientific and technological interest because of the unique chemical and physical properties they often display, such as low-dimensional magnetism, charge density wave phenomena, and superconductivity [1]. In addition, because the anisotropic properties of these compounds can often be dramatically altered through modest modifications in composition and crystal structure, they can be ideal materials for investigating the relationships between composition, crystal structure, chemical bonding, and material properties. With the discovery of the first layered ternary nitride phase, NaTaN2, by Jacobs and von Pinkowski [2], there has been increasing interest in exploring other layered nitride compositions and structural motifs. With respect to the more well known oxide and sulfide analogues, the expectations are that the layered ternary and higher order nitrides will display novel crystal structures, unusual cation-anion bonding arrangements, and a diverse collection of magnetic, optical, and electrical properties. The tailoring of advanced materials for a specific application often relies on the ability to substitute a particular element directly into a specific crystallographic site. Since the coordination preference of a given element depends on its size, oxidation state, and electronegativity, theoretically it should be possible to determine a priori what type of substitution is allowable in a given compound and what properties are likely to result. In practice, however, the chemistry of site-specific substitution remains to date largely experimental in nature. In compounds with several equivalent cation coordination sites, substitution experiments afford the only means of ascertaining which elements may be inserted into a certain site. These types of experiments have been conducted on a vast number of oxide, sulfide, and boride systems. However, with the exception of attempting to de-intercalate and re-intercalate lithium in LiMoN2
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