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

Abstract

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, β-SiAlON was prepared, the yield of which was determined by XRD measurements. At 1500 and 1550°C in the CRN process, single-phase β-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 χ-SiAlON were obtained using other preparation conditions. The concentration of Mg2+ in the gel affected the yield and z value of β-SiAlON, that is, the yield and the z value increased with increasing concentration of Mg2+ in the gel. From energy dispersive X-ray analysis (EDX), it was found that no Mg was present in β-SiAlON prepared above 1500°C. The process of the formation of β-SiAlON above 1400°C is postulated on the basis of X-ray diffraction and EDX analyses.