| 摘要 |
PURPOSE:To obtain a silicon nitride base sintered compact having high strength from room temp. to a high temp. and excellent in oxidation resistance and creep resistant property by making a sintered compact consisting mainly of silicon nitride, containing a specific element and having a specific crystal phase as a main phase. CONSTITUTION:The silicon nitride base sintered compact consists mainly of silicon nitride and contains 1-10mol% group IIIa element in periodic table, in which at least Lu is contained, expressed in terms of oxide per the whole, and is 1.6-3.5 in the mol ratio (SiO2/RE2O3) of impurity oxide expressed in terms of SiO2 to group IIIa element expressed in terms of oxide (RE2O3) and has a grain boundary phase consisting of the crystal phase composed of group IIIa element, silicon and oxygen as the main phase. The firing is executed in the sintering condition at the temp. of 1500-2000 deg.C under nitrogen pressure, at which silicon nitride is not decompose. Further, when the sintering temp. exceeds 2000 deg.C, the crystal growth of the silicon nitride occurs to induce the deterioration of strength. |
