ELECTRON-ENERGY-LOSS NEAR-EDGE STRUCTURE (ELNES) ON THE CARBON K-EDGEIN TRANSITION-METAL CARBIDES WITH THE ROCK-SALT STRUCTURE

The mono-carbides of the 3d, 4d and 5d transition metals of groups IVA (Ti, Zr, Hf) and VA (V, Nb, Ta) of the periodic table have the rock s alt (B1) structure. They are-found in many technologically important s ystems. The binary compounds exist over a range of compositions, norma lly with a deficit of carbon. Since their structures are identical and their lattice parameters similar, there is considerable mutual solubi lity between then so that a wide range of compounds of the form MC(x) exist where M is a mixture of transition metals. This paper presents a comparison of the electron energy loss near edge structure (ELNES) on the carbon K-edges from the binary carbides with compositions close t o stoichiometry. The spectra show systematic changes of the ELNES and the threshold energy as the metal species is changed. The threshold en ergy and intensity increase on going from group IVA to group VA. Equiv alent features can be identified in the spectrum from each compound. T he energy of each feature, relative to the threshold energy, varies sy stematically with the lattice parameter of the compound. The systemati c change in the ELNES with composition has potential applications wher e mixed metal carbides, nitrides and carbo-nitrides co-exist. In such cases, it can be difficult to obtain an unambiguous interpretation of microanalytical data and ELNES offers one more channel of information.