SILICON NITRIDE SINTERED COMPACT AND PRODUCTION THEREOF

PURPOSE: To obtain a sintered compact of silicon nitride which has mechanical properties sufficient to be used as a part for motor vehicles from room temperature up to elevated one and parts for a gas turbine engine, particularly excellent in flexural strength at from room temperature to 1,000 deg.C. CONSTITUTION: This sintered compact of silicon nitride comprises the main phase of β-silicon nitride crystals and the grain boundary phase containing rare-earth elements, silicon, aluminum, oxygen and nitrogen where Si2 N2 O particles of 5-20μm average particle size are dispersed in the grain boundary phase. A molded compact containing, as auxiliary components, 1-10wt.% silicon oxide of less than 3μm average particle size together with rare earth element oxides and aluminum oxide is heated at 800-1,400 deg.C under a reduced pressure lower than 10Torr to precipitate Si2 N2 O particles, then sintered at 1,600-1,900 deg.C in a non-oxidizing atmosphere.