US5588992A
Expired / Lapsed
US
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Conversion of doped polycrystalline material to single crystal material
Assignee: General Electric Co
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Filing: 1995-11-03
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Granted: 1996-12-31
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Expires: 2015-11-03
Abstract
Abstract A solid state method of converting a polycrystalline ceramic body to a single crystal body includes the steps of doping the polycrystalline ceramic material with a conversion-enhancing dopant and then heating the polycrystalline body at a selected temperature for a selected time sufficient to convert the polycrystalline body to a single crystal. The selected temperature is less than the melting temperature of the polycrystalline material and greater than about one-half the melting temperature of the material. In the conversion of polycrystalline alumina to single crystal alumina (sapphire), examples of conversion-enhancing dopants include cations having a +3 valence, such as chromium, gallium, and titanium. The polycrystalline body further can be inhomogeneously doped to form a first portion of the polycrystalline body that is doped to the selected level of the conversion-enhancing dopant and a second portion that is not doped such that heating the doped polycrystalline body causes conversion of first portion to a single crystal structure and the second portion retains a polycrystalline structure.
Inventors
- 👤 Curtis E. Scott
- 👤 Mary Sue Kaliszewski
- 👤 Lionel M. Levinson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:23
CPC Classifications
C; C30; C30B; C30B1/00; C30B29/00; C30B29/10; C30B29/16; C30B29/20
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
104 words
A solid state process for convening a polycrystalline ceramic body doped with a selected conversion-enhancing dopant at a selected concentration to a single crystal body comprising the steps of: doping at least a portion of the polycrystalline ceramic material comprising said ceramic body with a conversion-enhancing dopant to a selected concentration; and heating the doped polycrystalline body to a selected temperature to convert the portion of the polycrystalline body doped to said selected concentration to a single crystal structure, said selected temperature being above one-half of the melting temperature of said doped ceramic material but below the melting temperature of said doped ceramic material.
Claim 2
Dependent Claim
104 words
A solid state process for convening a polycrystalline ceramic body doped with a selected conversion-enhancing dopant at a selected concentration to a single crystal body comprising the steps of: doping at least a portion of the polycrystalline ceramic material comprising said ceramic body with a conversion-enhancing dopant to a selected concentration; and heating the doped polycrystalline body to a selected temperature to convert the portion of the polycrystalline body doped to said selected concentration to a single crystal structure, said selected temperature being above one-half of the melting temperature of said doped ceramic material but below the melting temperature of said doped ceramic material.
Claim 3
Dependent Claim
37 words
A process according to claim 1 wherein the step of doping the polycrystalline ceramic material comprising said ceramic body comprises doping a bisque-fired precursor of said polycrystalline ceramic body with said conversion-enhancing dopant to said selected concentration.
Claim 4
Dependent Claim
55 words
A process according to claim 2 wherein the step of doping said bisque-fired precursor comprises immersing said bisque-fired precursor in a liquid solution having a concentration necessary to achieve said conversion of said conversion-enhancing dopant and allowing said dopant to penetrate into said bisque-fired precursor to said selected concentration of dopant in said bisque-fired precursor.
Claim 5
Dependent Claim
45 words
A process according to claim 1 wherein the step of doping the polycrystalline ceramic material-comprising said ceramic body comprises the steps of doping a starting powder with a selected level of said selected conversion-enhancing dopant; and processing said starting powder to form said ceramic body.
Claim 6
Dependent Claim
34 words
A process according to claim 1 wherein said selected concentration of said conversion-enhancing dopant is less then that concentration which will result in the formation of a second crystalline phase in said polycrystalline material.
Claim 7
Dependent Claim
29 words
A process according to claim 1 wherein the step of doping said polycrystalline material further comprises the steps of dispersing said conversion-enhancing dopant homogeneously in said polycrystalline ceramic body.
Claim 8
Dependent Claim
43 words
A process according to claim 1 wherein the step of heating said doped polycrystalline body further comprises the steps of: sintering said polycrystalline body to remove conversion-impeding impurities; and heat treating said polycrystalline body to convert said dense body to a single crystal.
Claim 9
Dependent Claim
40 words
A process according the claim 7 wherein the steps of sintering said polycrystalline body, heat treating said polycrystalline body to remove conversion-impeding impurities, and heat treating said polycrystalline body to convert the body to single crystal comprise multiple heating cycles.
Claim 10
Dependent Claim
41 words
A process according the claim 7 wherein the steps of sintering said polycrystalline body, heat treating said polycrystalline body to remove conversion-impeding impurities, and heat treating said polycrystalline body to convert the body to single crystal comprise respective distinct heating cycles.
Claim 11
Dependent Claim
42 words
A process according the claim 7 wherein the steps of sintering said polycrystalline body, heat treating said polycrystalline body to remove conversion-impeding impurities, and heat treating said polycrystalline body to convert the body to single crystal comprise a single continuous heating cycle.
Claim 12
Dependent Claim
17 words
A process according to claim 1 wherein said polycrystalline body is in the shape of a fiber.
Claim 13
Dependent Claim
17 words
A process according to claim 1 wherein said polycrystalline body is in the shape of a tube.
Claim 14
Dependent Claim
77 words
The process of claim 1 wherein the step of doping at least a portion of said ceramic body with a conversion-enhancing dopant to a selected concentration further comprises doping said a first portion of said ceramic body and not doping a second portion of said ceramic body such that the step of heating said body produces a composite material body comprising a single crystal structure in said first portion and a polycrystalline structure in said second portion.
Claim 15
Dependent Claim
136 words
The process of claim 1 wherein the step of doping at least a portion of said ceramic body with a conversion-enhancing dopant to a selected concentration further comprises doping a first portion of said ceramic body with said dopant to said selected concentration and doping a second portion of said ceramic body with said dopant to a second phase level concentration; said second phase level concentration being greater than the solid solubility level of said dopant in polycrystalline ceramic material such that a second phase is formed along grain boundaries of said second portion of said doped body so as to inhibit the conversion process; wherein the step of heating of said body produces a composite material body in which said first portion comprises a single crystal structure and said second portion comprises a polycrystalline structure.
References Cited (Backward Citations)
US988230A
Cited
US3026210A
Cited
US3564328A
Cited
US3943324A
Cited
US4046618A
Cited
US3998687A
Cited
US4150317A
Cited
US4519870A
Cited
US4980236A
Cited
US4285732A
Cited
US4444615A
Cited
JPS6221794A
Cited
JPS6228118A
Cited
JPS62278198A
Cited
US4900393A
Cited
US5129029A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-12-31 | 2000-07-01 | 2000-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-12-31 | 2004-07-01 | 2004-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-12-31 | 2008-07-01 | 2008-12-31 | $7700.00 | Window Closed / Lapsed |