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

Phase compositions, densification, microstructures, thermal conductivities, and mechanical properties of sintered reaction-bonded Si3N4 (SRBSN) and sintered Si3N4 (SSN) using the same additives and procedure were compared. The present results showed that the density of SRBSN with MgO-Y2O3 additives was much lower than that of SSN with the same additives. The Eu2O3-MgO-Y2O3 additives inhibited the densification, while the ZrO2-MgO-Y2O3 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 ZrO2-MgO-Y2O3 as aids. The SSN with relative density of 99.0% and thermal conductivity of 56.8 Wm−1 K−1 was fabricated using ZrO2-MgO-Y2O3 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 Si3N4 ceramics.