PURPOSE: To reduce deformation of the ceramics sintered body by placing a molded body on a floor plate made of an Si3N4-based ceramics sintered body and introducing the molded body into a heat resistant vessel and roasting it in a N2 atmosphere of normal pressure or pressurization in a closed state.
CONSTITUTION: After adding and mixing the proper amount of a sintering adjuvant selected from among MgO, Al2O3 and Y2O3, etc., and water with Si3N4 powder, the mixture is dried and the dry powder is molded into a required shape. The molded body having a volume of at least 5% for a vessel is placed on a floor plate made of an Si3N4-based ceramics sintered body and introduced into a heat resistant vessel such as a cover-fitted crucible made of carbon and covered and then inserted into a sintering furnace in a practically closed state. Thereafter the molded body is roasted for a prescribed time at 1700-1900°C in the N2 atmosphere of normal pressure or at 1800-2000°C in the pressurized N2 atmosphere of 0.5-10 MPa. Thereby an Si3N4-based ceramics sintered body is obtained which is little in deformation and has a high density.
AKIYAMA YUTAKA
TSUKAMOTO KEIZO
YAMAGISHI SENJO
