Quartz glass crucible for pulling a single crystal

摘要

A quartz glass crucible for pulling a single crystal, which comprises a cylindrical straight portion, a bottom portion and a curved intermediate portion for connecting the straight portion and the bottom portion. The straight portion has an opaque area positioned within about 75% or less of the total height of the crucible, measured from the upper open end of the crucible. The opaque area in the straight portion has a total bubble volume which ranges from about 7*10-3 cm3/cm3 to 30*10-3 cm3/cm3. The remaining straight portion, the curved intermediate portion and the bottom portion consist of two layers. One layer is an inner transparent layer having a total volume of bubbles of about 4*10-3 cm3/cm3 or less and corresponds to from about 20% to 60% of the thickness of the crucible, measured from the inside surface thereof. The other layer is an outer opaque layer having a total volume of bubbles ranging between about 7*10-3 cm3/cm3 and 30*10-3 cm3/cm3, which is integral with the opaque area of the upper part of the straight portion.