| 摘要 |
PURPOSE:To obtain a silicon nitride sintered compact reduced in the variation in characteristics, by mixed molding of Si3O4 with a sintering auxiliary followed by calcining in an N2 atmosphere to form a specific open porosity, then calcining under a higher N2 gas pressure to effect lower open porosity and by sintering under a lower N2 gas pressure at elevated temperatures. CONSTITUTION:Si3O4 powder 0.3-1.5mum in mean particle diameter is mixed with a sintering auxiliary such as Y2O3 so as to account for 0.5-20wt.% of the total quantity followed by molding to specified shape. This form is calcined in an N2 gas atmosphere at <=2 atm at 1600-1700 deg.C to from an open porosity of <=2%. The resulting sintered compact is calcined in an N2 gas atmosphere at 30-200atm and at 1700-1900 deg.C to form an open porosity of <=1%. The resulting sintered compact is then calcined in an N2 gas atmosphere at 10-100atm which is lower than the pressure in the 2nd calcining process and at 1700-2000 deg.C which is higher than the temperature in the 2nd calcining process, and subsequently, if needed, heat-treated in an N2 gas atmosphere at <=1000atm at 1500-1900 deg.C to effect densification, thus obtaining the objective Si3N4 sintered compact reduced in the variation in characteristics even in its mass production. |
