PRODUCTION OF BETA-TYPE SINTERED SILICON NITRIDE

摘要

PURPOSE:To obtain a beta-type sintered silicon nitride having low void defect content and excellent strength and toughness by using inexpensive beta-type silicon nitride powder as a raw material. CONSTITUTION:A powdery raw material consisting of alpha-type and beta-type silicon nitride powder and containing >=80wt.% of the beta-type silicon nitride is incorporated with 0.2-20wt.% of one or more kinds of oxide or nitride selected from the oxide of the group IIIa element of the periodic table, aluminum oxide, magnesium oxide, calcium oxide, zirconium oxide and aluminum nitride and subjected to the primary sintering process comprising the baking under nitrogen gas pressure of <=100atm at 1600-2100 deg.C until the porosity decreases to <=10%. The product is subjected to the secondary sintering by baking at 1800-2100 deg.C under a nitrogen gas pressure higher than that of the primary sintering process until the porosity decreases to <=5%.