Structural determination of sintered Si3N4/SiC nanocomposite using the XPS differential charge effect

We report a study using X-ray Photoemission Spectroscopy (XPS) of a nanocomposite which is a mixture of silicon nitride (Si3N4) micrometric grains (mean diameter of 0.2 µm) and silicon carbide (SiC) nanoparticles (from 0.01 µm to 0.06 µm). A differential charge effect was detected in this compound for the C1s and Si2p core levels. We concluded that the existence of such an effect was because the first raw acquired spectra display selective partial reductions of the charge for 6-7 h. Contributions to the XPS core levels from silicon carbide (Si-C4 and C-Si4) are not affected by charge shifts, in contrast to other contributions. This differential charge effect was not observed for SiCN nanopowders which display a rigid charge shift of all the contributions in the same core levels. This is a good fingerprint for the structural organization in the compound. We concluded the existence of SiC nanoparticles dispersed in a vitreous YSiAlON[C] phase located at the grain boundaries in the material which made up a conducting cement/skeleton surrounding large silicon nitride grains (0.2 µm).