Tailoring the thermal conductivity and mechanical properties of gas pressure sintered Si₃N₄ ceramics by changing nitrogen pressure

Tailoring the multi-physical properties of silicon nitride (Si₃N₄) ceramics is important for their application in power device packaging. To achieve this goal, herein, dense Si₃N₄ was prepared via gas pressure sintering (GPS), and the thermal and mechanical properties were successfully tailored by changing the nitrogen (N₂) pressure. The effects of N₂ pressure on the composition, linear shrinkage, microstructure, thermal conductivity and mechanical properties were systematically explored. The increasing N₂ pressure elevated the N/O ratio in the intergranular phase and reduced the β-Si₃N₄ grain size and aspect ratio. The near-full relative density for the Si₃N₄ ceramics was realized at 2 MPa or above. A splendid combination of high thermal conductivity (>79.40 W m⁻¹ K⁻¹), flexural strength (>890 MPa) and fracture toughness (>6.60 MPa m^1/2) was achieved for the Si₃N₄ ceramics prepared under 2–4 MPa N₂ pressure. The results provide a facile method for regulating the multi-physical properties of Si₃N₄.