RAW POWDER FOR SILICON NITRIDE SINTERED BODY, SINTERED BODY USING THE POWDER AND ITS PRODUCTION

摘要

PURPOSE:To reduce the thickness of a discolored layer by forming the raw powder consisting of Si3N4, SiO2, a sintering assistant formed with the elements having specified atomic number, total weight and weight ratio and impurities and sintering the formed product. CONSTITUTION:Si3N4 raw powder and a sintering assistant are mixed so that the ratio of the total weight of the impurity constituting elements such as B and C in the Si3N4 raw powder consisting of Si3N4 and SiO2 and the elements of =21 atomic number among the elements constituting the sintering assistant such as Li2O and BeO to the total weight of the elements of =20 atomic number other than Si, N and O is controlled to =5 to obtain the raw powder for an Si3N4 sintered body. The raw powder is press-formed into a formed product, and the product is primarily calcined in gaseous N2, the product is subjected to the hot isostatic pressing process at about 1650 deg.C and about 1800atm in gaseous N2 to obtain an Si3N4 sintered body. Alternatively, the raw powder is coated with gas-impermeable glass, and then subjected to the hot isostatic pressing process at about 1800 deg.C and about 2000 atm to obtain the Si3N4 sintered body.