Rapid fabrication of Si3N4 ceramics by reaction-bonding and pressureless sintering

Abstract Phase compositions, densification, microstructures, thermal conductivities, and mechanical properties of sintered reaction-bonded Si 3 N 4 (SRBSN) and sintered Si 3 N 4 (SSN) using the same additives and procedure were compared. The present results showed that the density of SRBSN with MgO-Y 2 O 3 additives was much lower than that of SSN with the same additives. The Eu 2 O 3 -MgO-Y 2 O 3 additives inhibited the densification, while the ZrO 2 -MgO-Y 2 O 3 additives promoted the densification. The SRBSN with relative density of 99.5% and thermal conductivity of 66.5 Wm −1  K −1 was rapidly prepared using ZrO 2 -MgO-Y 2 O 3 as aids. The SSN with relative density of 99.0% and thermal conductivity of 56.8 Wm −1  K −1 was fabricated using ZrO 2 -MgO-Y 2 O 3 additives. The comparable density and higher thermal conductivity made the SRBSN prepared rapidly from low cost Si starting powder superior over the SSN. This study suggested that the SRBSN route with a combination of nitridation catalyst and densification aids provided a promising route to fabricate cost-effective Si 3 N 4 ceramics.