US4251206A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for and method of supporting a crucible for EFG growth of sapphire
Assignee: RCA Corp
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Filing: 1979-05-14
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Granted: 1981-02-17
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Expires: 1999-05-14
Abstract
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.
Inventors
- 👤 Samuel Berkman
- 👤 Robert Metzl
- 👤 Richard E. Novak
- 👤 David L. Patterson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 23:18
CPC Classifications
F; F27; F27B; F27B14/00; F27B14/08; F27B2014/0825; F27M; F27M2001/00; F27M2001/03; Y; Y10; Y10S; Y10S117/00; Y10S117/90; Y10T; Y10T117/00; Y10T117/10; Y10T117/1024; Y10T117/1032; Y10T117/1036; Y10T117/1044
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
185 words
A crucible support structure for supporting a crucible which is to be heated to at least 1800° 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° 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° 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° C. even when said support crucible is maintained at a temperature in excess of 1800° C.
Claim 2
Dependent Claim
185 words
A crucible support structure for supporting a crucible which is to be heated to at least 1800° 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° 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° 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° C. even when said support crucible is maintained at a temperature in excess of 1800° C.
Claim 3
Dependent Claim
17 words
The crucible support structure recited in claim 1 wherein said support means comprises a fused silica pedestal.
Claim 4
Dependent Claim
16 words
The crucible support structure recited in claim 2 wherein said pedestal comprises a fused silica tube.
Claim 5
Dependent Claim
47 words
The crucible support structure recited in claim 3 wherein said pyrolytic graphite crucible support plate is thick enough so that the main body of said silica pedestal is maintained at a temperature of less than 1000° C. where the crucible is at a temperature of 1800° C.
Claim 6
Dependent Claim
12 words
The support structure recited in claim 3 wherein said tube is cylindrical.
Claim 7
Dependent Claim
16 words
The support structure recited in claim 1 wherein said support means comprises a fused silicon tube.
Claim 8
Dependent Claim
28 words
The crucible support structure recited in claim 1 further comprising a metal plate on said support surface for spacing said crucible from said pyrolytic graphite crucible support plate.
Claim 9
Dependent Claim
29 words
The crucible support structure recited in claim 7 wherein said metal plate comprises tungsten and said structure further comprises a molybdenum ring spacing said crucible from said tungsten plate.
Claim 10
Dependent Claim
29 words
The crucible support structure recited in claim 1 wherein said structure is capable of stably supporting a crucible which is maintained at a temperature of at least 2100° C.
Claim 11
Dependent Claim
44 words
The crucible support recited in claim 1 wherein: said pryolytic graphite crucible support plate is substantially circular disk; a plurality of substantially radially inwardly extending slits are spaced along the periphery of said disk; and said slits extend through the thickness of said disk.
Claim 12
Dependent Claim
40 words
The crucible support structure recited in claim 10 wherein said slits extend radially inward from the periphery of said disk at least as far as the expected location of the wall of the crucible to be supported by said plate.
Claim 13
Dependent Claim
27 words
The crucible support recited in claim 1 including a sinterable heat shield supported on the outer periphery of said support surface such that it surrounds said crucible.
Claim 14
Dependent Claim
35 words
The crucible support recited in claim 12 wherein said sinterable heat shield is made of pyrolytic graphite having its C axis extending generally perpendicular to the C axis of said pyrolytic graphite crucible support plate.
Claim 15
Independent Claim
198 words
A method of supporting a crucible which is at a temperature of at least 1800° 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° 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° 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° C. when said crucible is maintained at a temperature of at least 1800° C.
Claim 16
Independent Claim
198 words
A method of supporting a crucible which is at a temperature of at least 1800° 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° 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° 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° C. when said crucible is maintained at a temperature of at least 1800° C.
Claim 17
Dependent Claim
23 words
The method recited in claim 14 wherein the main body of said pedestal is maintained at a temperature of less than 1000° C.
Claim 18
Dependent Claim
14 words
The method recited in claim 14 wherein said pedestal is comprised of fused silica.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-17 | 1984-08-18 | 1985-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-17 | 1988-08-18 | 1989-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-17 | 1992-08-18 | 1993-02-17 | $7700.00 | Window Closed / Lapsed |