Infrared spectra and structure of Si3N4, Si2ON2, and sialons

Sialon powders are prepared from Kyshtymskoe kaolin with 12 - 28 wt.% carbon mixtures by the carbo-thermal reduction-nitridation method. The infrared spectra of beta-, O'-, X- and 15R-phases in the Si-Al-O-N system are recorded and compared with the IR spectra of Si3N4, Si2ON2, and kaolin. The IR data are shown to correlate with the chemical composition of sialons and provide information supplementary to x-ray phase analysis data. The spectra of sialon powders differ from each other and from the spectrum of silicon nitride.