Study on Y‐Mg‐Si alloy additives to improve the thermal conductivity of Si₃N₄ by efficient deoxygenation

Using Y‐Mg‐Si alloy as a sintering additive, Si 3 N 4 ceramics were prepared by hot‐pressing sintering combined with atmospheric pressure heat treatment. The effects of alloy additive content on the densification, microstructure, thermal conductivity, and mechanical properties of hot‐pressed sintered Si 3 N 4 ceramics were studied. Si 3 N 4 ceramics with a density greater than 96% can be prepared by hot‐pressing sintering at 1750°C for 2 h with an alloy as a sintering additive. With the increase of additive content, the density increases first and then decreases, and the grain size increases gradually. By preferentially reacting with the inherent SiO 2 on the surface of Si 3 N 4 , the alloy additive improves the N/O ratio of the sintered liquid phase and reduces the effect of lattice oxygen on the thermal conductivity. Finally, the thermal conductivity of 52.7 W·m −1 ·K −1 was achieved at the content of 6 wt% alloy additive, which was 22% higher than that of 43.2 W·m −1 ·K −1 of pure oxide additive; It's hardness and fracture toughness are 16.1 GPa and 9.63 MPa·m 1/2 , respectively. After heat treatment at 1850°C for 5 h, the thermal conductivity increased to 67.2 W·m −1 ·K −1 . Using Y‐Mg‐Si alloy as a sintering additive is an effective method to prepare high strength and high thermal conductivity Si 3 N 4 ceramics, which provides a new idea for the preparation of high thermal conductivity Si 3 N 4 ceramics.