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

We report a study using X-ray Photoemission Spectroscopy (XPS) of a nanocom posite which is a mixture of silicon nitride (Si3N4) micrometric grains (me an diameter of 0.2 mu m) and silicon carbide (SiC) nanoparticles (from 0.01 mu m to 0.06 mu m). A differential charge effect was detected in this comp ound for the C1s and Si2p core levels. We concluded that the existence of s uch 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 l evels from silicon carbide (Si-C-4 and C-Si-4) are not affected by charge s hifts, 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 t he grain boundaries in the material which made up a conducting cement/skele ton surrounding large silicon nitride grains (0.2 mu m). (C) 2000 Elsevier Science B.V, All rights reserved.