Densification, microstructure, thermal and mechanical properties of Si3N4 ceramics: Effect of Y2Si4N6C and MgSiN2 content

The rapid development of third-generation semiconductors urgently requires ceramic substrates with excellent performance. In this work, silicon nitride (Si3N4) ceramics were successfully prepared via gas-pressure sintering (GPS) using Y2Si4N6C and MgSiN2 as additives. The influence of Y2Si4N6C-MgSiN2 content on the liquid phase properties and microstructure of Si3N4 ceramics was clarified. The use of Y2Si4N6C-MgSiN2 not only did not introduce additional oxygen but also consumed SiO2 and purified the beta-Si3N4 lattice. The increase in N/O formed a nitrogen-rich liquid phase, which led to the microstructure of Si3N4 ceramics having a bimodal distribution. The relationship between different degrees of bimodal microstructure and properties was explored. When the Y2Si4N6C-MgSiN2 content was 9 wt%, Si3N4 ceramics obtained excellent thermal and mechanical properties due to lattice purification, Si3N4/Si3N4 continuity increase, the largest average grain diameter, and a bimodal distribution microstructure with moderate grain size distribution. The thermal conductivity was 116.7 W m(-1) K-1, the fracture toughness was 10.7 +/- 0.35 MPa m(1/2), and the bending strength was 767 +/- 29.6 MPa.