| 摘要 |
PURPOSE:To provide an optical parts having high rigidity and high corrosion resistance and a high reflectivity at need by using silicon nitride or sialon which is sintered with rare earth elements, group III elements and magnesium as a sintering assistant, has substantially a specific ratio of a sialon phase or silicon nitride phase after sintering and has a specific relative density. CONSTITUTION:The optical parts are obtd. by using the silicon nitride or sialon 2 which is sintered with at least >=1 kinds among. the group III elements contg the rare earth elements and the magnesium or the compds. thereof as the sintering assistant, has substantially >=80% sialon phase or silicon nitride phase after sintering and has >=92% relative density and forming the silicon nitride or the sialon to a necessary shape by polishing. The surface of at least a part of this sintered compact 2 is smoothly worked, by which the optical parts having the high rigidity and the high corrosion resistance are obtd. The smooth surface is coated with a reflection film 1 at need, by which the high reflectivity is obtd. |
