Single phase silicon carbide refractory

The present invention provides a method of pressureless sintering silicon carbide in which the silicon carbide starting material is in the form of a multimodal composition, or mixture, of coarse and submicron particles. The present sinterable silicon carbide mixtures consist of separate fractions of sized particles. Each fraction is present in amounts of from about 5 to about 75% by weight of the mixture, and more preferably from about 10 to about 65% by weight of the mixture. One fraction has a particle size ranging between about 0.21 mm (210 microns) to about 3.4 mm (3400 microns) and preferably the larger particles have a size less than about 2.4 mm. A second fraction has a particle size ranging between about 0.003 mm (3 microns) up to about 0.21 mm. A third fraction has a size less than 0.003 mm, but has an average size less than 1 micron. The present products are produced by sintering particulate silicon carbide in the presence of a sintering aid and a slight excess carbon. Generally, sintering temperatures range from about 1900 DEG C. to about 2300 DEG C. depending upon the sintering atmosphere.