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US4518545A
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Method for sintering high density yttria-gadolinia ceramic scintillators
Assignee: General Electric Co
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Filing: 1982-06-18
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Granted: 1985-05-21
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Expires: 2002-06-18
Abstract
Abstract A method for preparing high density yttria-gadolinia ceramic scintillators by cold-pressing multicomponent powder to form powder compacts and then sintering the compacts to form transparent-to-translucent ceramic scintillator bodies. The powder compacts are formed by either die pressing or die pressing followed by isostatic pressing to further increase green density. The powder compacts are sintered in vacuum or a reducing atmosphere at a temperatue of between 1800° C. and 2100° C. The preferred heating sequence includes a holding period at a temperature lower than the final sintering temperature. The finished scintillator includes Y 2 O 3 , Gd 2 O 3 , and one or more of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Pr 2 O 3 , and Tb 2 O 3 rare earth activator oxides. At least one of the oxides of elements Zr, Th, and Ta is included as a transparency promoting densifying agent. At least one of CaO and SrO may be included as a light output restorer.
Inventors
- 👤 Dominic A. Cusano
- 👤 Charles D. Greskovich
- 👤 Frank A. DiBianca
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 09:03
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/645; C04B35/6455; C04B35/50; C04B35/505; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7783; C09K11/7784; C09K11/7787; G; G01; G01T; G01T1/00; G01T1/16; G01T1/20; G01T1/202; G01T1/2023; Y; Y10; Y10S; Y10S264/00; Y10S264/91
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
165 words
A method for preparing a transparent-to-translucent yttria-gadolinia polycrystalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder consisting essentially of between 5 and 50 mole percent Gd 2 O 3 , between about 0.02 and 12 mole percent of at least one rare earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent power being Y 2 O 3 ; cold pressing said multicomponent powder to form a powder compact; and sintering said powder compact in either a reducing atmosphere or vacuum to yield a transparent-to-translucent polycrystalline ceramic body.
Claim 2
Independent Claim
165 words
A method for preparing a transparent-to-translucent yttria-gadolinia polycrystalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder consisting essentially of between 5 and 50 mole percent Gd 2 O 3 , between about 0.02 and 12 mole percent of at least one rare earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent power being Y 2 O 3 ; cold pressing said multicomponent powder to form a powder compact; and sintering said powder compact in either a reducing atmosphere or vacuum to yield a transparent-to-translucent polycrystalline ceramic body.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said transparency promoter comprises between about 0.2 and 0.7 mole percent ThO 2 .
Claim 4
Dependent Claim
20 words
The method of claim 1 wherein said transparency promoter comprises between about 0.2 and 0.7 mole percent ZrO 2 .
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein said transparency promoter comprises between about 0.1 and 0.5 mole percent Ta 2 O 5 .
Claim 6
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 20 and 40 mole percent Gd 2 O 3 .
Claim 7
Dependent Claim
19 words
The method of claim 1 wherein said light output restorer comprises between about 0.2 and 4 mole percent CaO.
Claim 8
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 1 and 6 mole percent Eu 2 O 3 .
Claim 9
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 0.05 and 1.5 mole percent Nd 2 O 3 .
Claim 10
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 0.05 and 3 mole percent Tb 2 O 3 .
Claim 11
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 0.1 and 2 mole percent Yb 2 O 3 .
Claim 12
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprises between about 0.03 and 1 mole percent Dy 2 O 3 .
Claim 13
Dependent Claim
22 words
The method of claim 1 wherein said multicomponent powder comprised between about 0.02 and 0.05 mole percent Pr 2 O 3 .
Claim 14
Dependent Claim
19 words
The method of claim 1 wherein said light output restorer comprises between about 0.1 and 3 mole percent SrO.
Claim 15
Dependent Claim
55 words
The method of claim 1 wherein said step of preparing said multicomponent power comprises mixing high purity, micron-to-submicron powders of Gd 2 O 3 , Y 2 O 3 , at least one of said rare earth activator oxides, at least one of said transparency promoters, and at least one of said light output restorers.
Claim 16
Dependent Claim
75 words
The method of claim 1 wherein said step of preparing said multicomponent powder comprises the steps of: coprecipitating by the wet chemical oxalate process the oxalates of Y, Gd, and at least one of said rare earth activator oxides; calcining said oxalates so as to obtain the corresponding oxides; and mixing at least one of said transparency promoters and at least one of said light output restorers with said oxides obtained in said calcining step.
Claim 17
Dependent Claim
19 words
The method of claim 15 wherein said step of calcining is preceded by the step of milling said oxalates.
Claim 18
Dependent Claim
20 words
The method of claim 15 or 16 further comprising the step of milling said oxides obtained in said calcining step.
Claim 19
Dependent Claim
36 words
The method of claim 15 wherein said step of calcining comprises the step of heating said oxalates in air at a temperature of between 700° C. and 900° C. for between 1 hour and 4 hours.
Claim 20
Dependent Claim
34 words
The method of claim 1, 14, or 15 wherein said step of cold pressing comprises the step of die pressing said multicomponent powder at a pressure of between about 3,000 psi and 15,000 psi.
Claim 21
Dependent Claim
44 words
The method of claim 19 wherein said step of cold pressing further comprises the step of isostatically pressing the die pressed multicomponent powder at a pressure of between about 10,000 psi and 60,000 psi to further increase the green density of said powder compact.
Claim 22
Dependent Claim
56 words
The method of claim 20 wherein said step of sintering comprises the steps of: heating said powder compact at a rate of between about 100° C. per hour and 700° C. per hour to a sintering temperature of between 1800° C. and 2100° C.; and holding said sintering temperature for between about 1 and 30 hours.
Claim 23
Dependent Claim
89 words
The method of claim 20 wherein said step of sintering comprises the steps of: heating said powder compact at a rate of between 300° C./hr and 400° C./hr to a holding temperature of between 1600° C. and 1700° C.; maintaining said holding temperature for between 1 and 20 hours and then increasing the temperature at a rate of between 25° C./hr and 75° C./hr to a final sintering temperature of between 1800° C. and 2100° C.; and maintaining the final sintering temperature for between about 1 and 10 hours.
Claim 24
Dependent Claim
30 words
The method of claim 22 further comprising the step of cooling the resulting polycrystalline ceramic scintillator body to room temperature over a period of between about 2 and 10 hours.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1988-05-20 | 1988-11-19 | 1989-05-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-20 | 1992-11-19 | 1993-05-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-20 | 1996-11-19 | 1997-05-21 | $7700.00 | Window Closed / Lapsed |