| 摘要 |
PURPOSE:To obtain the titled sintered material having excellent high-temperature strength and useful as parts for automobile engine, etc., by precipitating one or more kinds of hexagonal crystal of Y5N(SiO4)3, etc., and YAG (5Al2O3.3Y2O3) crystal at the sintered grain boundary of a specified Si3N4 sintered material. CONSTITUTION:A powder mixture of raw material is produced by mixing powder raw material for Si3N4 with powder of an Al compound and powder of a Y compound such as Y2O3. The raw material mixture is sintered to precipitate (A) one or more compounds selected from Y5N(SiO4)3, Y10N2(SiO4)6 and Y20 N4(SiO4)12 having hexagonal crystal form and (B) YAG (5Al2O3.3Y2O3) crystal at the grain boundary of the sintered raw material mixture. The sintered Si3N4 produced by this process exhibits an X-ray diffraction pattern wherein the intensity ratio of the maximum diffracted X-ray caused by the above hexagonal crystal and YAG crystal to that of the B-Si3N4 crystal is 0.02-3. |
