| 摘要 |
PURPOSE:A porous gel prepared by hydrolysis of a metal alkoxide is partially sintered first, then heated in an atmosphere containing chlorine at a temperature lower than the above one and sintered at a temperature higher than that of chlorine treatment to produce the objective optical glass of greatly reduced chlorine content. CONSTITUTION:After gelation of a mixture of a metal alkoxide such as Si(OCH3)4, methanol and water, the remaining water and methanol are distilled off to form a gel of, e.g., a cylinder. The gel is partially sintered in a helium-containing atmosphere, then heat treated in a chlorine-containing atmosphere at a temperature lower than that of the partial sintering, 400-1,000 deg.C, e.g., at 800 deg.C. Then, the heat treated gel is additionally sintered in a helium-containing atmosphere at a temperature higher than that of the chlorine treatment. The amounts of hydroxyls and chlorine in the resultant optical glass reduces so that foaming is prevented on sintering. |
