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

Si₃N₄ ceramics with enhanced thermal conductivity and mechanical properties were prepared by using nitride sintering additives of YN and MgSiN₂. In addition to the conventional oxide sintering additives such as Y₂O₃ and MgO, the use of nitride sintering additives offered more possibilities for the optimization of the microstructure and properties of Si₃N₄ ceramics. The Si₃N₄ sample with binary nitride additives of YN‒MgSiN₂ 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 Si₃N₄ 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 Si₃N₄ 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.