High-pressure sintering of a solid solution of carbon in SiC

Submicron powder of a solid solution of carbon in silicon carbide was synthesized and characterized by x-ray diffraction, electron microscopy, and Raman scattering spectroscopy. The dissolution of carbon was found to reduce the lattice parameter of SiC from 4.359 to 4.353 Angstrom. The structural perfection of the powder particles and the bonding configuration of the dissolved carbon are assessed, and the structural changes induced in the solid solution by vacuum annealing and high-pressure sintering are considered. Sintering the SiC-C powder under optimal conditions yields ceramics with a hardness of about 40 GPa and a fracture toughness as high as 9.5 MPa m(1/2).