US3764643A
Expired / Lapsed
US
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Method for sintering very pure yttria compacts to transparency
Assignee: Hitachi Ltd
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Filing: 1970-11-20
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Granted: 1973-10-09
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Expires: 1990-11-20
Abstract
Abstract Finely divided Yttria having a purity of at least 99.99 percent is pressed into compacts, sintered in dry hydrogen or a partial vacuum to temperatures in the range of 2,150*-2,330*C, and refired in wet hydrogen at a temperature of from 1,950*-2,300*C to reoxidize any yttria that was reduced to yttrium during sintering. A dense body transparent to visible light is produced. If a transparent article is not desired, the purity can be reduced.
Inventors
- 👤 A Muta
- 👤 Y Tsukuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:37
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/50; C04B35/505; Y; Y10; Y10S; Y10S264/00; Y10S264/91
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
98 words
treating said molded body to form said transparent polycrystalline body by the steps which consist of: a. heating the molded body in a non-oxidizing thoroughly dry atmosphere selected from the group consisting of hydrogen and vacuum at a temperature of about 2,150* to 2,330*C. for at least about 30 minutes to effect sintering thereof; and b. refiring the resultant sintered body in a hydrogen atmosphere having a dew point of higher than 0*C. at a temperature of from 1,950* to 2,300*C. for a period of time not less than several minutes to effect decoloring of said sintered body.
Claim 2
Dependent Claim
45 words
A method according to claim 1, wherein the heating step is carried out in a hydrogen atmosphere having a dew point of not higher than -20*C. at a temperature of from 2,200* to 2,300*C. for a period of time of not less than 60 minutes.
Claim 3
Dependent Claim
23 words
A method according to claim 1, wherein the heating step is carried out under the vacuum of at least 10 2 mm Hg.
Claim 4
Dependent Claim
15 words
A method according to claim 3, wherein the vacuum is about 10 4 mm Hg.
Claim 5
Dependent Claim
44 words
A method according to claim 1, further comprising the step of retaining the molded body, before the heat sintering step, in a vacuum of not higher than 10 2 mm Hg at a temperature of from 100* to 250*C. for at least 10 minutes.
Claim 6
Dependent Claim
21 words
A method according to claim 5, wherein the molded body is retained in said vacuum for about 10 to 60 minutes.
References Cited (Backward Citations)
US3545987A
Cited
US3640887A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |