Effect of Diluents on Post-Reaction Sintering of Silicon Nitride Ceramics

摘要

Post-reaction sintering as a technique for the fabrication of Si_3N_4 ceramics has received much attention as a cost-effective process due to the use of cheap Si powder as a raw material. In this method, the rapid exothermic nitridation of Si results in local melting of Si to cause its agglomeration, which is expected to be a flaw after densification. Therefore, control of the exothermic reaction is needed to improve the reliability of post-reaction sintered Si_3N_4 ceramics. In this study, Si_3N_4 ceramics were fabricated by post-reaction sintering with Si_3N_4 or SiO_2 powders in order to control the exothermic reaction. As a result, the microstructure and bending strength of Si_3N_4 ceramics was changed by adding these additives. In particular, the addition of SiO_2 resulted in the high strength of Si_3N_4 ceramics. Consequently, it was found that Si_3N_4 and SiO_2 particles played the role of diluents, and SiO_2 was effective in post-reaction sintering as an oxygen donor.