Production of polycrystalline shaped bodies comprising alpha - and/or ss-silicon carbide by pressureless sintering

摘要

In the sintering process of the invention for producing polycrystalline shaped bodies comprising alpha - and/or ss-silicon carbide of high density from preformed green bodies, germanium and/or gallium as sintering aid and also carbon are mixed into the pulverulent silicon carbide having a particle size of equal to or less than 5 mu m, the mixture is preformed and sintered at a temperature of from 1900 to 2300@C, with the proportion of sintering aid being between 0.1 and 3% by weight, based on the silicon carbide. The shaped bodies obtained have a high density of more than 98.5 % of the theoretical density, have a finely crystalline microstructure and possess flexural strengths of at least 600 N/mm<2>. The mode of fracture is transcrystalline.