Phase Identification in Carbon and BN Systems by EELS

Abstract

Electron energy-loss spectroscopy measurements have been made on carbon and BN polymorphs, as well as on a number of borides, carbides and nitrides present in sintered cBN based compacts. The similarity in crystal symmetry between carbon and the isotructural BN system results in spectral similarities in both the low-loss features and electron energy-loss near-edge structure associated with the particular core-loss ionization edges. ELNES features hold information on the nearest neighbour environment of the excited atom in a given phase. It is shown that the analysis of these features provides characteristic coordination fingerprints for the identification of carbon and BN allotropes. Similarly, the comparison of ELNES features associated with B-K, C-K and N-K ionization edges provides fingerprints for the identification of B in TiB 2 and B 4 C, C in TiC and B 4 C, and Nin AlN, TiN and BN, respectively. An attempt is made to quantify the fraction of sp 5 bonding in diamond-like carbon and cBN based cutting tool material from the relative intensity of the π resonance in C-K and B-K ELNES, respectively