Synthetic quartz powder, its production process, and synthetic quartz crucible

Abstract

The amount of residual carbon and hydroxyl groups in a synthetic quartz powder made by a wet process is reduced by baking the synthetic quartz powder in a low pressure atmosphere. Quartz glass crucibles made using the synthetic quartz powder have low bubble contents, and are particularly suited for growing single crystals.

1 - 6 . (canceled)  
     
     
         7 . A synthetic quartz powder made by a process comprising baking a silica gel powder made by a wet process, or a synthetic quartz powder made from the silica gel powder, under a low pressure atmosphere at a pressure of less than 100 Pa and at a baking temperature in a range higher than a temperature at which decarbonization occurs and lower than a temperature at which sintering occurs, wherein the synthetic quartz powder has a carbon content of less than 2 ppm and a hydroxyl group content of less than 50 ppm.  
     
     
         8 . A quartz glass crucible made using a synthetic quartz powder, wherein 
 at least a part of an inside surface of the crucible is made using the synthetic quartz powder of  claim 7  as a raw material.    
     
     
         9 . A quartz glass crucible made from a synthetic quartz powder, wherein 
 at least a part of an inside surface of the crucible is made using the synthetic quartz powder of  claim 7;  and    a bubble content in a transparent glass layer less than 0.5 mm thick forming the inside surface of the crucible is less than 0.1%.    
     
     
         10 . A synthetic quartz powder made by a process comprising 
 baking a silica gel powder, made by a wet process, to form a synthetic quartz powder, where the baking is in air at atmospheric pressure and at a temperature in a range higher than a temperature at which hydroxyl groups are removed from the silica gel powder and lower than a temperature at which the silica gel powder sinters; and    baking the synthetic quartz powder under a low pressure atmosphere at a pressure of less than 100 Pa and at a baking temperature in a range higher than a temperature at which decarbonization of the synthetic quartz powder occurs and lower than a temperature at which the synthetic quartz powder sinters, wherein    the synthetic quartz powder has a carbon content of less than 2 ppm and a hydroxyl group content of less than 50 ppm.    
     
     
         11 . A quartz glass crucible made using a synthetic quartz powder, wherein 
 at least a part of an inside surface of the crucible is made using the synthetic quartz powder of  claim 10  as a raw material.    
     
     
         12 . A quartz glass crucible made from a synthetic quartz powder, wherein 
 at least a part of an inside surface of the crucible is made using the synthetic quartz powder of  claim 10;  and    a bubble content in a transparent glass layer less than 0.5 mm thick forming the inside surface of the crucible is less than 0.1%.