Abstract: Taking brown alumina, silicon nitride and carbon silicon as raw materials, the specimens were prepared under oxidization atmosphere. The specimens was embedded in carbon at temperatures of 1500 ℃,1550 ℃ and 1600 ℃ for 5 h respectively. The phase change of the specimens fired under oxidation atmosphere and the stability of Si_3N_4 under carbon-embedded were studied by XRD, SEM and EDS, combining with thermodynamic analysis.The results show that there is a mullite solid solution Si_6Al_(10)O_(21)N_4 created after fired under oxidation atmosphere.Si_3N_4 and Si_6Al_(10)O_(21)N_4 will transform to SiC partly after carbon-embedded, and the transition temperature of Si_3N_4 and Si_6Al_(10)O_(21)N_4 are above 1500 ℃ and 1550 ℃ respectively.

Key words: Si_3N_4;SiC;phase transition