Mold for producing silica crucible
There is provided a mold for use in the production of a silica crucible by heat-fusing silica or quartz powder attached onto an inner wall of a rotating mold, wherein an inner side of an upper opening portion of the mold corresponding to an upper part of the silica crucible is ground to obtain a step portion and a ring-shaped heat insulating barrier member having an inner diameter smaller than that of the mold is disposed on the step portion through a hollow disk-shaped support member having an inner diameter equal to or somewhat larger than that of the heat insulating barrier member.
1. A mold for use in the production of a silica crucible, comprising:
a step portion on an inner side of an upper opening portion of the mold; and
a ring-shaped heat insulating barrier member having an inner diameter smaller than that of the mold is disposed on the step portion through a hollow disk-shaped support member having an inner diameter equal to or larger than that of the heat insulating barrier member.
2. A mold for use in the production of a silica crucible according to claim 1 , wherein the barrier member is made of silica.
3. A mold for use in the production of a silica crucible according to claim 1 , wherein the support member is made of carbon or composite of carbon and ceramics.
4. A mold for use in the production of a silica crucible according to claim 1 , wherein a protruding thickness t 1 of an inner surface of the ring-shaped barrier member from an inner peripheral wall of the mold, which is defined by t 1 =(inner diameter of mold−inner diameter of barrier member)/2, is 20 to 80% of an attached thickness t 2 of silica or quartz powder.
5. A mold for use in the production of a silica crucible according to claim 1 , wherein an inner surface of the barrier member has a surface roughness of 6.3 to 25 μm as an arithmetic mean roughness Ra.
6. A mold for use in the production of a silica crucible according to claim 1 , wherein the support member is of onepiece-type or split-type.
7. A mold for use in the production of a silica crucible according to claim 1 , wherein the step portion of the mold is at a location corresponding to an upper part of the silica crucible.
8. A mold for use in the production of a silica crucible according to claim 1 , wherein the mold is used in a rotating mold method.