Preparation of Si3N4 ceramics with enhanced thermal conductivity and mechanical properties using nitride sintering additives

Si 3 N 4 ceramics with enhanced thermal conductivity and mechanical properties were prepared by using nitride sintering additives of YN and MgSiN 2 . In addition to the conventional oxide sintering additives such as Y 2 O 3 and MgO, the use of nitride sintering additives offered more possibilities for the optimization of the microstructure and properties of Si 3 N 4 ceramics. The Si 3 N 4 sample with binary nitride additives of YN‒MgSiN 2 showed a coarse-grained microstructure and the maximum thermal conductivity of 112 W m −1 K −1 after heat treatment. However, the binary nitride additives were insufficient to supply sufficient liquid phase during the sintering of Si 3 N 4 ceramics, which caused porosity and impaired the mechanical properties. A good balance between thermal conductivity and mechanical properties was achieved by using nitride-oxide hybrid sintering additives of YN‒MgO, where the Si 3 N 4 sample showed both high thermal conductivity of 109 W m⁻ 1 K⁻ 1 and good mechanical properties with flexural strength of 707 ± 7 MPa, fracture toughness of 9.5 ± 0.2 MPa m 1/2 , and Vickers hardness of 14.9 ± 1 GPa.