Highly pure opaque quartz glass, a method for its production and its use

摘要

The high-purity, opaque quartz glass containing 3×10.sup. 6 -9. times.10.sup.6 of closed cells having an average size of 20-40 &mgr; m per 1 cm.sup.3, a ratio of closed cells having sizes of 100 &mgr;m or more to the whole of cells being 1% or less, thereby showing 5% or less of linear transmittance for near infrared rays (&lgr;=900 nm) at a thickness of 1 mm is produced by compacting amorphous silica powder having an average particle size of 0.5-10 &mgr;m, in which each of impurities selected from Li, Na, K, Fe, Ti and Al is 1 ppm or less, if any, and sintering the resultant green body at 1730°-1850° C.