CHARACTERIZATION OF SILICON CARBIDE-SILICON NITRIDE COMPOSITE ULTRAFINE PARTICLES SYNTHESIZED USING A CO2-LASER BY SI-29 MAGIC-ANGLE-SPINNING NMR AND ESR

The structure of silicon carbide-silicon nitride (SiC-Si3N4) composite particles synthesized using a CO2 laser was studied by magic angle spinning nuclear magnetic resonance (MAS-NMR) and electron spin resonance (ESR). The structure around Si atoms changed by introducing N. C atoms around Si were substituted by N atoms, and N-rich configurations around Si atoms increased stepwise as the N content increased. The low N content composite particles consisted of mainly SiC phase containing dissolved N. N atoms were partly present in beta-SiC microcrystal and partly in the grain boundary layer in the particle. N atoms were tetrahedrally surrounded by four Si atoms in beta-SiC microcrystal and were trivalent state bonded to three Si atoms in the grain boundary layer. The high N content particles consisted of SiC, Si3N4, and amorphous phases, whose amount depended on N content.