ABSTRACT Silicon nitride ceramics are attractive candidates for substrate applications because they combine electrical insulation, mechanical robustness, and the capacity for efficient heat dissipation. Their practical thermal conductivity, however, is often restricted by lattice oxygen defects and grain‐boundary phases generated during processing. In the present study, MgSiN 2 was incorporated into a Yb 2 O 3 –MgO additive system to regulate oxygen‐related defects and to tailor the liquid‐phase sintering behavior of Si 3 N 4 ceramics fabricated by gas‐pressure sintering at 1850°C. The effects of MgSiN 2 content on densification, phase evolution, microstructural development, room‐temperature thermal conductivity, and mechanical properties were systematically examined. The specimen containing 4 wt.% MgSiN 2 displayed the most balanced overall performance, with a relative density of 96.17%, a flexural strength of 912 MPa, a fracture toughness of 8.1 MPa·m 1/2 , and a Vickers hardness of 13.6 GPa. When the MgSiN 2 level was further increased to 6 wt.%, the room‐temperature thermal conductivity rose to 83.1 W·m −1 ·K −1 , although the mechanical properties deteriorated because of reduced densification and microstructural coarsening. These results show that controlled MgSiN 2 addition provides an effective route for adjusting the oxygen state, microstructure, and overall performance of Si 3 N 4 ceramics.
Ma et al. (Wed,) studied this question.