Electrically conductive Si₃N₄ bonded SiC: effect of Fe₂O₃, MoO₃, and SiC particle size

The effects of initial SiC particle size on the electrical resistivity, thermal conductivity, and flexural strength of SiC when combined with Fe₂O₃ and MoO₃ additives were investigated. Each batch contained 10 wt% Fe₂O₃ as a sintering additive. The addition of MoO₃ (0–2 wt%) and variation in sintering temperature (1200–1400 °C) collectively influenced the electrical resistivity, while the thermal conductivity, air flow permeability and flexural strength was predominantly affected by the SiC particle size. The samples sintered at 1300 °C with 1 wt% of MoO₃ showed an electrical resistivity, a thermal conductivity, and a flexural strength of 2.1 × 10^–1 Ω cm, 21 W/m K, 59 MPa, respectively, for 4.5 μm SiC, and 3.1 × 10^–1 Ω cm, 30 W/m K, 25 MPa, respectively, for 30 μm SiC. The in-situ formation of a network-like structure of secondary conductive phases such as Fe₃Si along with the diffusion of N₂ reduced the electrical resistivity, whereas the formation of Si₃N₄ improved the mechanical properties. The designed composition showed excellent extrudability, forming a square honeycomb structure, verifying its large-scale viability for novel applications, such as heatable filters and electrically conductive catalytic supports.