Effect of a new nonoxide additive, Y3Si2C2, on the thermal conductivity and mechanical properties of Si3N4 ceramics

Enhancement of the thermal conductivity of silicon nitride is usually achieved by sacrificing its mechanical properties (bending strength). In this study, β-Si 3 N 4 ceramics were prepared using self-synthesized Y 3 Si 2 C 2 and MgO as sintering additives. It was found that the thermal conductivity of the Si 3 N 4 ceramics was remarkably improved without sacrificing their mechanical properties. The microstructure and properties of the Si 3 N 4 ceramics were analyzed and compared with those of the Y 2 O 3 -MgO additives. The addition of Y 3 Si 2 C 2 eliminated the inherent SiO 2 and introduced nitrogen to increase the N/O ratio of the grain-boundary phase, inducing Si 3 N 4 grain growth, increasing Si 3 N 4 grain contiguity, and reducing lattice oxygen content in Si 3 N 4 . Therefore, by replacing Y 2 O 3 with Y 3 Si 2 C 2 , the thermal conductivity of the Si 3 N 4 ceramics was significantly increased by 31.5% from 85 to 111.8Wm −1 K −1 , but the bending strength only slightly decreased from 704 ± 63MPa to 669 ± 33MPa.