| 摘要 |
PURPOSE:To obtain silicon nitride powder capable of providing a sintered body having high strength at elevated temp. by sintering even under normal pressure by specifying an oxygen content, specific surface area, mean particle size, and a content of fine powder of the silicon nitride powder. CONSTITUTION:The title silicon nitride powder is characterized by <=0.7wt.% oxygen content, >=6m<2>/g specific surface area, <=1mu mean particle size, and <=7vol.% content of fine powder having <=0.2mu particle size. If the oxygen content is >0.7wt.%, sufficiently grown beta-columnar crystals having a large aspect ratio are hardly obtainable because alpha-beta transition to be caused during sintering causes easily at a low temp., increasing a content of intergranular layer in which a sintering aid is to be formed, and causing variation of solubility of silicon nitride. If the specific surface area is <6m<2>/g, the product is difficultly sinterable resulting insufficient denseness. If the mean particle size is >1mu, the solubility of silicon nitride into compound oxides which generate by the reaction with the oxygen in the sintering aid, decreases, so the product is not sufficient in denseness. If the content of the fine powder having <=0.2mu particle size is too much, a strength at elevated temp. is not recognized. |
