PURPOSE: To obtain the titled high-purity glass which is available for optical fiber or the like and excellent in optical homogeneity by heat-treating a specified porous sintered body in inert gas and/or an air current contg. gaseous halogen to melt, dropping it on a plate and thereafter cooling and vitrifying it.
CONSTITUTION: A porous sintered body 1 preferably having 30W70% porosity is obtained by packing a mixture of powder of a solid-phase raw material which is prepared so as to become glass composition consisting of e.g. 49% (mol., hereinafter the same) ZrF4, 25% BaF2, 3.5% LaF3, 2% YF3, 2.5% AlF3 and 18% LiF in a cylindrical vessel made of carbon and inserting a supporting rod 2 made of platinum thereinto and sintering it e.g. at about 450°C for about 5hr in inert gas. Then this sintered body 1 is set in a core pipe 4 made of platinum via the platinum rod 2 so that it is not brought into contact with the wall of the vessel and heat-treated e.g. at about 450°C for about 2hr via a melting furnace 3 of the sintered body in inert gas contg. ≤100ppm water content and/or an air current contg. gaseous halogen. The droplets are dropped on a platinum plate 6 held at about 250°C by a heat insulating furnace 5 of glass and cooled to obtain a transparent multicomponental glass block 7.
SAKAGUCHI SHIGEKI
OISHI YASUTAKE
