| 摘要 |
PURPOSE:To obtain a high toughness silicon nitride-based sintered compact hardly lowering its mechanical strength even in a hot oxidizing atmosphere by compacting a powdery mixture consisting of erbium oxide, zircon and silicon nitride, sintering the resulting compact, under specified conditions and forming a Zr3Er4O12 crystal phase as a grain boundary phase by a specified means. CONSTITUTION:A powdery mixture consisting of 5-15wt.% erbium oxide (Er2O3) 1-20wt.% zircon (ZrSiO4) and the balance silicon nitride (Si3N4) is compacted. The resulting compact is sintered at 1,700-2000 deg.C in an atmosphere of gaseous nitrogen and a Zr3Er4O12 crystal phase is formed as a grain boundary phase by adopting <=5 deg.C/min cooling rate in a cooling stage after sintering, holding the sintered compact for >=2hr within the temp. range of 1,500-1,700 deg.C in a cooling stage after sintering or carrying out reheating by holding for >=2hr within the temp. range of 1,500-1,700 deg.C in a nitrogen atmosphere after sintering. |
