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

Abstract

AbstractThe silicon nitride (Si3N4) 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 Si3N4 fabricated by HPFS were investigated. As the strain increased from 67% to 167%, the mean grain diameter of Si3N4 with MgSiN2 as an additive increased by 49%, reaching 1.36 ± .6 µm. The addition of MgSiN2–Y2O3 resulted in a significantly stronger degree of texturing and smaller grain diameter in Si3N4, compared to the incorporation of MgSiN2 alone. The thermal conductivity of Si3N4 with added MgSiN2–Y2O3 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 Si3N4 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.