Effects of Gd2O3 and MgSiN2 sintering additives on the thermal conductivity and mechanical properties of Si3N4 ceramics

Abstract Si 3 N 4 ceramics were prepared by gas pressure sintering at 1900°C for 12 h under a nitrogen pressure of 1 MPa using Gd 2 O 3 and MgSiN 2 as sintering additives. The effects of the Gd 2 O 3 /MgSiN 2 ratio on the densification, microstructure, mechanical properties, and thermal conductivity of Si 3 N 4 ceramics were systematically investigated. It was found that a low Gd 2 O 3 /MgSiN 2 ratio facilitated the thermal diffusivity of Si 3 N 4 ceramics while a high Gd 2 O 3 /MgSiN 2 ratio benefited the densification and mechanical properties. When the Gd 2 O 3 /MgSiN 2 ratio was 1:1, Si 3 N 4 ceramics obtained an obvious exaggerated bimodal microstructure and the optimal properties. The thermal conductivity, flexural strength, and fracture toughness were 124 W·m −1 ·k −1 , 648 MPa, and 9.12 MPa·m 1/2 , respectively. Comparing with the results in the literature, it was shown that Gd 2 O 3 ‐MgSiN 2 was an effective additives system for obtaining Si 3 N 4 ceramics with high thermal conductivity and superior mechanical properties.