Patent US5588992A successfully refreshed from Google Patents.
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 23:06
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.
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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) | 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 |