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Monolithic SiC and SiC-AlN composites were prepared by liquid-phase sintering. Polytypes of SiC, transformation of its polytypes and microstructure of the sintered materials were investigated. The SiC-AlN composites were composed of the 2H phase with dispersed SiC grains. The microstructure of sintered monolithic SiC varied depending on the polytypes of the starting SiC powders, α and β, as well as on the sintering conditions. The SiC-AlN composites showed the microstructure irrespective of the initial phase of SiC. The 2H phase was a SiC-AlN solid solution and had a spherical grain shape, and the 4H-SiC had a platelike shape.