Influence of Fe2O3 and sintering atmosphere on the phase evolution, and electrical resistivity of porous SiC

Abstract

The effects of Fe2O3 addition on the electrical resistivity, thermal conductivity, and microstructure formation of SiC processed under Ar, N2, and N2 + 5% H2 sintering atmospheres were investigated. The use of N2 + 5% H2 resulted in the lowest electrical resistivity, improved thermal conductivity and enhanced flexural strength of SiC as compared to Ar and N2. The use of 10 wt% Fe2O3 resulted in an electrical resistivity of 3.8 × 10−1 Ω cm, a thermal conductivity of 20 W/m.K, and a flexural strength of 40 MPa with 33% porosity of samples sintered at 1250 °C under N2 + 5% H2. The in-situ formation of a network-like structure of iron silicide (Fe3Si) at contact points of SiC yielded a conductive path and reduced the electrical resistivity, while the formation of Si3N4 improved the mechanical property. Although, all sintering atmospheres resulted in the formation of electrically conductive Fe3Si, but the use of N2 + 5% H2 produced samples with highest Si3N4 content, lowest amount of oxide phase (SiO2 and Si2N2O), and additionally densified the microstructure.