Effect of atmosphere on the reaction sintering of Si2N2O

Abstract The reaction sintering of Si 2 N 2 O from an equimolar mixture of Si 3 N 4 and SiO 2 with 5 wt% Al 2 O 3 addition was investigated in 98 or 980 kPa N 2 at 1600–1850°C. At the initial stage, Si 3 N 4 densification occurred through a liquid phase of SiO 2 Al 2 O 3 system. Further densification was observed together with the formation and exaggerated grain growth of Si 2 N 2 O. High N 2 pressure was useful for the prevention of thermal decomposition of Si 2 N 2 O and bloating of the compact. Among various packing powders, which have various SiO partial pressures, an equimolar mixture of Si 3 N 2 O and SiO 2 was the most effective for the densification. The effect of N 2 and packing powder on reaction sintering of Si 2 N 2 O was discussed in relation to observed kinetics and thermodynamic calculations. Bending strength of sintered materials was 310–320 MPa.