Influence of Mg2+ on the formation of β-SiAlON by the carbothermal reduction-nitridation of homogeneous gel

Homogeneous gels with Al-O-Si bonds were prepared by, the sol-gel method using aluminum iso-propoxide (AIP) and silicon ethoxide (TEOS) containing Mg2+ added as Mg(NO3)(2). Via carbothermal reduction-nitridation (CRN) of the as-prepared gels, beta -SiAlON was prepared, the yield of which was determined by XRD measurements. At 1500 and 1550 degreesC in the CRN process, single-phase beta -SiAlON was prepared from the precursor gel with a molar ratio (Mg(NO3)(2)/(AIP+TEOS)) of 0.5 and 1.0, respectively. Mullite and chi -SiAlON were obtained using other preparation conditions. The concentration of Mg2+ in the gel affected the yield and z value of beta -SiAlON, that is, the yield and the z value increased with increasing concentration of lqg" in the gel. From energy dispersive X-ray analysis (EDX), it was found that no Mg was present in beta -SiAlON prepared above 1500 degreesC. The process of the formation of beta -SiAlON above 1400 degreesC is postulated on the basis of X-ray diffraction and EDX analyses. (C) 2001 Elsevier Science: Ltd. All rights reserved.