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US4273587A
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US
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Polycrystalline transparent spinel sintered body and a method for producing the same
Assignee: NGK Insulators Ltd
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Filing: 1979-08-08
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Granted: 1981-06-16
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Expires: 1999-08-08
Abstract
Abstract Polycrystalline spinel sintered body consisting mainly of Al 2 O 3 and MgO in a molar ratio of Al 2 O 3 /MgO of ranging from 0.52/0.48 to 0.70/0.30 and containing 0.001-0.1% by weight of LiF has a high in-line transmission. The sintered body can be obtained by calcining a powdery mixture of Al 2 O 3 and MgO in a specifically limited molar ratio, molding the calcined mixture into a shaped article together with a specifically limited amount of LiF, and firing the shaped article under a specifically limited temperature condition.
Inventors
- 👤 Isao Oda
- 👤 Masayuki Kaneno
- 👤 Issei Hayakawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:06
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/10; C04B35/111; C04B35/115; C04B35/44; C04B35/443
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
38 words
A polycrystalline transparent spinel sintered body consisting mainly of Al 2 O 3 and MgO in a molar ratio of Al 2 O 3 /MgO of ranging from 0.52/0.48 to 0.70/0.30, and containing 0.001-0.1% by weight of LiF.
Claim 2
Dependent Claim
38 words
A polycrystalline transparent spinel sintered body consisting mainly of Al 2 O 3 and MgO in a molar ratio of Al 2 O 3 /MgO of ranging from 0.52/0.48 to 0.70/0.30, and containing 0.001-0.1% by weight of LiF.
Claim 3
Independent Claim
143 words
A method of producing a polycrystalline transparent spinel sintered body, comprising mixing Al 2 O 3 with MgO or an aluminum compound with a magnesium compound, which are formed into Al 2 O 3 and MgO by calcination respectively, in a molar ratio of Al 2 O 3 /MgO of ranging from 0.50/0.50 to 0.525/0.475, calcining the mixture at 1,150°-1,300° C., mixing the calcined mixture with 0.01-0.2% by weight of LiF based on the amount of the calcined mixture, molding the resulting mixture into a given shape, subjecting the shaped article to a primary firing at 1,200°-1,400° C. and then to a secondary firing at 1,700°-1,900° C. under an atmosphere of hydrogen atmosphere, vacuum or an inert gas atmosphere, wherein a temperature-raising rate is not higher than 100° C./hr within the temperature range between the primary firing step and the secondary firing step.
Claim 4
Independent Claim
143 words
A method of producing a polycrystalline transparent spinel sintered body, comprising mixing Al 2 O 3 with MgO or an aluminum compound with a magnesium compound, which are formed into Al 2 O 3 and MgO by calcination respectively, in a molar ratio of Al 2 O 3 /MgO of ranging from 0.50/0.50 to 0.525/0.475, calcining the mixture at 1,150°-1,300° C., mixing the calcined mixture with 0.01-0.2% by weight of LiF based on the amount of the calcined mixture, molding the resulting mixture into a given shape, subjecting the shaped article to a primary firing at 1,200°-1,400° C. and then to a secondary firing at 1,700°-1,900° C. under an atmosphere of hydrogen atmosphere, vacuum or an inert gas atmosphere, wherein a temperature-raising rate is not higher than 100° C./hr within the temperature range between the primary firing step and the secondary firing step.
Claim 5
Dependent Claim
13 words
The polycrystalline transparent spinel sintered body produced by the method of claim 2.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-06-15 | 1984-12-15 | 1985-06-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-06-15 | 1988-12-15 | 1989-06-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-06-15 | 1992-12-15 | 1993-06-16 | $7700.00 | Window Closed / Lapsed |