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US 4,251,206 AGranted
Apparatus for and method of supporting a crucible for EFG growth of sapphire
AssigneeRCA Corporation
InventorsSamuel Berkman, Robert Metzl, Richard E. Novak, David L. Patterson
Life of this patent
Estimating the term…
Abstract
A crucible for containing a melt and die for EFG growth of sapphire is supported by a pyrolytic graphite crucible support plate having the C axis of the pyrolytic graphite perpendicular to the bottom of the crucible which is supported by the plate. This thermally insulates the crucible from the pedestal which supports the support plate.
Claims16
A crucible support structure for supporting a crucible which is to be heated to at least 1800.degree. C. comprising:
- a pyrolytic graphite crucible support plate having a support surface for supporting said crucible;
- support means for supporting the surface of said pyrolytic graphite crucible support plate opposite said support surface, said support means being made of a material having a relatively low coefficient of thermal expansion and a softening point of about 1140.degree. C. and being usable to retain said support surface in a relatively stable position when the temperature of said support means does not exceed about 1300.degree. C.;
- the C axis of said pyrolytic graphite crucible support plate extending between said support surface and said opposite surface such that it is substantially perpendicular to the bottom of said crucible;
- and
- said pyrolytic graphite having a thickness about said support surface and said opposite surface to prevent the portion of said support means engaged with said opposite surface from rising to a temperature in excess of about 1300.degree. C. even when said support crucible is maintained at a temperature in excess of 1800.degree. C.
2 more elements
A method of supporting a crucible which is at a temperature of at least 1800.degree. C. comprising:
- providing a pyrolytic graphite crucible support plate for supporting said crucible on a support surface thereon;
- supporting said pyrolytic graphite crucible support plate on a support pedestal made of a material having a relatively low coefficient of thermal expansion and a softening point of about 1140.degree. C. and being usable to retain said support surface in a relatively stable position when the temperature of said support means does not exceed about 1300.degree. C. by resting the face of said pyrolytic graphite crucible support plate opposite said support surface on an end portion of said support means;
- orienting said pyrolytic graphite crucible support plate so that the C axis of said pyrolytic graphite extends between said support surface and said opposite surface and is perpendicular to the bottom of a crucible supported thereby;
- and
- said pyrolytic graphite having a sufficient thickness between said support surface and said opposite surface to maintain the temperature of said end portion of the pedestal at a temperature of less than about 1300.degree. C. when said crucible is maintained at a temperature of at least 1800.degree. C.
2 more elements
Dependencies are inferred from the claim text.