Low temperature pressureless sintering of SiC-mullite composites

6H-SiC and α-Al₂O₃ powders were mixed as raw materials (in mass ratio of 7:3) with BaO and TiO₂ as sintering additives. The SiC-mullite composites were prepared via pressureless sintering in hydrogen atmosphere for 1 h after the green body was pre-oxidated at 1 200°C for 1 h. The effects of sintering temperature and BaO-TiO₂ content on the sintering properties and phase composition were investigated. The results show that the compactness improves obviously with the increase of sintering additives at sintering temperature of 1 500°C. The apparent porosity of the sample was 0.17% at BaO-TiO₂ additive of 8% (mass fraction). BaAl₂Si₂O₈ was generated via the reaction of BaO, α-Al₂O₃ and SiO₂ when the green body was pre-oxidated. During the sintering process, BaAl₂Si₂O₈ formed a liquid glass phase, which could promote sintering and the formation of mullite. The main crystal phase of the sample was 6H-SiC and mullite, and the minor phase was glass phase and Al₂SiO₅.