Microstructure tailoring of high thermal conductive silicon nitride through addition of nuclei with spark plasma sintering and post-sintering heat treatment

Abstract

High thermal conductive β-silicon nitride (β-Si3N4) ceramics were fabricated from fine α-Si3N4 powder as the raw material and coarse β-Si3N4 particles as the nuclei through spark plasma sintering (SPS) at 1650 °C for 5 min and post-sintering heat treatment at 1900 °C for 4 h. The microstructures of the sintered β-Si3N4 ceramics could be tailored with the nuclei. The mean sizes and frequencies of large grains increased and consequently decreased as the increased amount of coarse β-Si3N4 particles increased. The thermal conductivity of the sample with 10 mol% of β-Si3N4 nuclei reached a maximum value of 84.6 W m−1 K−1. These results revealed that the thermal conductivity of β-Si3N4 ceramics was independent of the grain size and controlled by the amount of reprecipitated large grains.