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