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

Abstract

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 β-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 m1/2, and the bending strength was 767 ± 29.6 MPa.