Layered ternary transition metal nitrides; synthesis, structure and physical properties

Two-dimensional structures are an emerging class of materials within nitride chemistry. We report here our systematic studies of two groups of these layered compounds: 1 Lithium transition metal compounds, Li(3-x-y)rectangle yMxN (M=Co, Ni, Cu, rectangle =Li vacancy) and 2 ternary transition metal nitrides of general formulation AMN(2) (A=alkaline earth metal, M=Ti, Zr, Hf). Compounds in class 1 are based on the hexagonal Li3N structure, unique to nit-ides. Compounds in group 2, by contrast, crystallise with oxide structures (alpha -NaFeO2 or KCoO2). Specific and unusual synthetic methods have been developed to reproducibly prepare these compounds. Compounds in series 1 contain ordered or disordered Li vacancies at increased levels relative to the parent Li3N, itself a Li+ fast ion conductor. Nitrides in series 2 should be nominally diamagnetic (S=0), yet magnetic measurements reveal behaviour seemingly inconsistent with this assumption. (C) 2001 Elsevier Science B.V. All lights reserved.