| 摘要 |
PURPOSE:To provide a silicon nitride sintered compact simultaneously improved in its strength and fracture toughness and comprising a texture composed of uniform fine crystal particles free from coarse particles and containing columnar crystals having large aspect ratios. CONSTITUTION:The silicon nitride sintered compact is characterized in that the silicon nitride in the basic phase comprises 66-99vol.% of beta-Si3N4 and the remaining amount of alpha-Si3N4, that the silicon nitride is composed of columnar crystals each having a minor axis diameter of <=500nm and an aspect ratio of 5-25 and cubic crystals having an average particle diameter of <=300nm, and that a titanium compound is contained in the crystal crystals of the basic phase and in the grain boundary phase. The silicon nitride sintered compact is produced by adding titanium oxide and a sintering auxiliary to alpha-Si3N4 powder, molding the mixture, subjecting the molded product to the first sintering treatment at 1300-1600 deg.C in an inert gas atmosphere, and subsequently subjecting the treated product to the secondary sintering treatment at 1400-1650 deg.C in an inert gas atmosphere under a pressure of >=10atm. |
