Vitreous silica crucible

Abstract

Provided is a vitreous silica crucible which can restrain inward collapse deformation at high temperature during pulling even when the crucible has a large opening diameter. The vitreous silica crucible has an outer layer made of natural fused silica and an inner layer made of synthetic fused silica. The straight body section is outwardly-widened upwardly. Preferably, the difference in inner diameter of the lower and upper ends of the outwardly-widened section is 0.1% or more. The inner layer made of synthetic fused silica on the corner section has a layer thickness which is 20% to 80% of the wall thickness of the central portion of the corner section. Preferably, the inner layer made of synthetic fused silica on the straight body section and the bottom section is thinner than that on the corner section.

1 . A vitreous silica crucible comprising:
 an outer layer made of natural fused silica; and   an inner layer made of synthetic fused silica, wherein the crucible comprises a straight body section, a corner section, and a bottom section, and the straight body section is outwardly-widened upwardly, the inner layer on the corner section has a layer thickness which is 20% to 80% of the wall thickness of a central portion of the corner section, and the inner layer on the straight body section and the bottom section is thinner than that on the corner section.   
     
     
         2 . The vitreous silica crucible of  claim 1 , wherein a difference in inner diameter of the lower and upper ends is 0.1% or more. 
     
     
         3 . The vitreous silica crucible of  claim 1 , wherein a range from an upper end of the straight body section to the corner section is outwardly-widened upwardly. 
     
     
         4 . The vitreous silica crucible of  claim 1 , wherein a range within 50 mm from an upper end of the straight body section is a vertical section, and a range from a lower end of the vertical section to the corner section is outwardly-widened upwardly. 
     
     
         5 . The vitreous silica crucible of  claim 1 , wherein a wall thickness of the straight body section is thinned toward an upper end section thereof.