Fabrication of silicon nitride with high thermal conductivity and flexural strength by hot‐pressing flowing sintering

Abstract The silicon nitride (Si 3 N 4 ) possessing enhanced thermal conductivity and flexural strength was sintered by a hot‐pressing flowing sintering (HPFS) method. The effects of extrusion deformation and sintering additives on the density, phase, microstructure, and performances of Si 3 N 4 fabricated by HPFS were investigated. As the strain increased from 67% to 167%, the mean grain diameter of Si 3 N 4 with MgSiN 2 as an additive increased by 49%, reaching 1.36 ± .6 µm. The addition of MgSiN 2 –Y 2 O 3 resulted in a significantly stronger degree of texturing and smaller grain diameter in Si 3 N 4 , compared to the incorporation of MgSiN 2 alone. The thermal conductivity of Si 3 N 4 with added MgSiN 2 –Y 2 O 3 increased to 109.1 W m −1 K −1 in the flow direction, and the flexural strength reached the maximum value of 1250.8 ± 39 MPa in the hot‐pressing direction. The results showed that the thermal conductivity and flexure strength of Si 3 N 4 were enhanced due to the formation of texture and the reduction of flaws induced by HPFS. Moreover, HPFS method exhibited outstanding controllability over the microstructures and properties of materials.