IR spectra and structure of Si-Al-O-N phases prepared by carbothermal reduction of kaolin in nitriding atmosphere

Abstract

Si–Al–O–N ceramics of different phase composition (dominated by the X-phase, β-sialon, or 15R-sialon) were prepared by carbothermal reduction of kaolin in nitriding atmosphere at different kaolin-to-carbon ratios. The intensity of absorption bands in the IR spectra of the sialon phases was shown to correlate with their chemical composition. The high strength of the Al–O absorption in the IR spectrum of the 15Rpolytypoid was interpreted as evidence for the presence of AlSiNO2bilayers (solid solution of Si and N in α-Al2O3).