| 摘要 |
PURPOSE:To improve strength, toughness and hardness of a sintered body by specifying the shorter diameter, alpha phase ratio and density of Si3N4 particles in a Si3N4 sintered body with a specified composition containing additive MgO and Y2O3. CONSTITUTION:An Si3N4 sintered body containing 80-94wt.% Si3N4, 2-10wt.% Hg (calculated as MgO) and 2-10wt.% Y (calculated as Y2O3) and having <=1mum shorter diameter of the Si3N4 particle in a ratio of >=90%, 5-40% alpha phase of Si3N4 and >=98% relative density. The above-mentioned sintered body is produced by blending 80-94wt.% powdery Si3N4 having <=1mum average diameter and >=80% alpha phase, 2-10wt.% Mg compound (calculated as MgO) and 2-10wt.% Y compound (calculated as Y2O3), molding the mixture, sintering the resultant molding at <=1600 deg.C in 1-20atm. N2 or an inert gas atmosphere (provided that >=1atm. N2 partial pressure) so as to be >=85% relative density and then carrying out secondary sintering of the resultant sintered substance at 1400-1600 deg.C in >=300atm. same atmosphere as as the above-mentioned one. |
