| 摘要 |
PURPOSE:To produce a sintered compact, reduced in deteriorating actions on high-temperature characteristics due to cationic impurities such as Al, Ca, Fe and Mg and excellent in high-pressure strength and creep resistance characteristics at a low cost. CONSTITUTION:This sintered compact is obtained by sintering a compact, containing silicon nitride as a principal component, a group IIIa element oxide (RE2O3) of the Periodic Table and silicon oxide (SiO2), composed at <=2 molar ratio expressed by SiO2/RE2O3 and further containing 10-10000ppm cationic impurities of Al, Fe, Ca and Mg at 1700-2000 deg.C temperature in an atmosphere containing nitrogen for >=3hr and then annealing the resultant sintered compact from the sintering temperature to 800 deg.C at <=15 deg.C/hr rate. The resultant sintered compact contains silicon nitride as a principal crystal phase, at least one crystal phase, containing a group IIIa element of the Periodic Table and selected from apatite, YAM and wollastonite in the grain boundary thereof and a part or all of the cationic impurities converted into a solid solution in the crystal phase of the grain boundary thereof. |
