PURPOSE: To obtain a silicon nitride base sintered compact excellent in strength and toughness even at the time of using β-type silicon nitride powder having much oxygen content.
CONSTITUTION: The silicon nitride sintered compact is obtained by adding 0.3(a-1.5)wt.% to 1.7(a-1.5)wt.% aluminum nitride and 2wt.% to 8wt.% of sum of magnesium oxide, aluminum oxide and at least one or more kinds of oxides of group IIIa elements in periodic table as an oxide sintering assistant to the silicon nitride powder containing (a)wt.% oxygen ((a) is ≥1.6 to ≤4), if necessary ≥0.1wt.% to ≤2wt.% Fe, ≥50wt.% β-type silicon nitride and the balance α-type silicon nitride and sintering at ≥1600°C to ≤2000°C under gaseous nitrogen pressure of 1atm to 500atm after molding.
HIROSAKI NAOTO
ANDO MOTOHIDE
NISSAN MOTOR