Free Access
Microsc. Microanal. Microstruct.
Volume 6, Number 1, February 1995
Page(s) 99 - 111
Microsc. Microanal. Microstruct. 6, 99-111 (1995)
DOI: 10.1051/mmm:1995110

Phase Identification in Carbon and BN Systems by EELS

Herbert K. Schmid

Div. Materials Science and Technology, CSIR, Pretoria/RSA, South Africa

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 $\rm TiB_2$ and $\rm B_4C$, C in TiC and $\rm B_4C$, and N in AlN, TiN and BN, respectively. An attempt is made to quantify the fraction of $\rm sp^3$ bonding in diamond-like carbon and cBN based cutting tool material from the relative intensity of the $\pi$ resonance in C-K and B-K ELNES, respectively.

7920K - Other electron surface impact phenomena.
6180M - Channelling, blocking and energy loss of particles.
6150K - Crystallographic aspects of polymorphic and order disorder transformations.
6160 - Crystal structure of specific inorganic compounds.
6155D - Crystal structure of specific nonmetallic elements.
6150E - Crystal symmetry: models and space groups, and crystalline systems and classes.
3520G - Molecular bond strengths, dissociation energies, hydrogen bonding.
6150L - Crystal binding.

Key words
bonds chemical -- boron compounds -- carbon -- crystal structure -- crystal symmetry -- electron energy loss spectra -- polymorphism -- phase identification -- EELS -- electron energy loss spectroscopy -- polymorphs -- sintered compacts -- borides -- carbides -- nitrides -- crystal symmetry -- low loss features -- electron energy loss near edge structure -- core loss ionization edges -- ELNES -- isostructural system -- nearest neighbour environment -- excited atom -- characteristic coordination fingerprints -- allotropes -- ionization edges -- sp sup 3 bonding -- diamond like C -- cutting tool material -- BN -- C -- TiB sub 2 -- B sub 4 C -- TiC -- AlN -- TiN

© EDP Sciences 1995