OPAQUE SILICA GLASS, ITS PRODUCTION AND SILICA GLASS MOLDED PRODUCT

摘要

PROBLEM TO BE SOLVED: To produce an opaque silica glass having a smooth surface and resistances to washing with a chemical and heat and durability. SOLUTION: This opaque silica glass is produced by keeping a quartz crystal powder having <=0.2 ppm contents of respective impurities of Na, K and Fe at a temperature for starting the melting of quartz to a melting temperature for cristobalite under a reduced pressure in a vacuum melt converting >=90 wt.% of quartz grains into silica glass and producing >=1 and <10 wt.% of cristobalite crystal grains. Thereby, the resultant opaque silica glass has grains composed of the cristobalite crystal grains dispersed in a silica glass matrix 2.19-2.24 g/cm3 bulk density, <=0.5 vol.% void ratio, <=0.2 ppm contents of the respective impurities of the Na, K and Fe, >=1 and <10 wt.% content of the cristobalite crystal phase and 5-100μm grain diameter of the grain size.