Anisotropies in microstructure and properties of Si3N4/BN composite ceramics: Synergistic effect of bimodal texture

Textured Si 3 N 4 /BN composite ceramics are prepared via combination of PHIP sintering and gas pressure sintering. The mechanical properties of composite ceramics gradually decrease with the increase of BN content. However, the bimodal texture of Si 3 N 4 /BN composite ceramics exhibits a synergistic effect on the anisotropy of thermal and mechanical properties. When the BN content is 20 vol%, The anisotropy of fracture toughness along different testing direction reaches 51.0 %. By the proper regulation of the bimodal texture, Si 3 N 4 /BN composite ceramics could simply realize a high thermal conductivity (99.2 W m −1  k −1 ) and thermal anisotropy (2.1) at low sintering temperature (1800 °C) for short preparation period (4 h). This bimodal texture breaks through the inhibition of the high thermal conductivity of Si 3 N 4 -based ceramics by the amorphous phase of low thermal conductivities. Thus, this new material designs have great advantages in large-scale preparation and directional heat dissipation in the next-generation electric devices.