Sintering and oxidation resistance of compositions in the SiC–La2O3–Al2O3–Cr2O3 system I. Pressureless sintering of compositions in the SiC–La2O3–Al2O3–Cr2O3 system at low temperatures

Sintering of materials, which were prepared from β-SiC and LaCrO3 with Al2O3, β-SiC and LaAlO3, β-SiC and LaAlO3 with Cr2O3 and Al2O3 via heating at 1700°C in graphite powder, was studied. Significant densification of material was achieved in SiC–LaCrO3–Al2O3 composition due to a formation of liquid phase. The formation of liquid phase is considered to be promoted by a reaction of chromium oxide with starting components. SiC–LaCrO3–Al2O3 compositions were sintered to about 90% of theoretical density at 1700°C. The material had a structure comprising a matrix made up of SiC grain with tiny LaAlO3 crystals and 2–4 μm inclusions of chromium carbide. As result, the material showed improved fracture toughness of 5 MPa m1/2 compared to that of SiC.