Patent US3635658A successfully refreshed from Google Patents.
US3635658A
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Rare earth oxide process
Assignee: GTE Sylvania Inc
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Filing: 1969-04-02
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Granted: 1972-01-18
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Expires: 1989-04-02
Abstract
Abstract A process for increasing the particle size of rare earth oxides is disclosed comprising: forming an aqueous mineral acid solution containing a rare earth source dissolved therein, reacting the rare earths in said solution with oxalic acid to form an insoluble rare earth oxalate, separating the rare earth oxalate from the reaction medium, contacting the rare earth oxalate with an aqueous oxalic acid solution having a concentration of oxalic acid of from about 1 to about 40 percent by weight and heating the rare earth oxalate to a sufficient temperature and time to convert said rare earth oxalates into rare earth oxides having a particle size of at least 3 microns.
Inventors
- 👤 John L Ferri
- 👤 James E Mathers
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 14:40
CPC Classifications
C; C01; C01F; C01F17/00; C01F17/20; C01F17/206; C01F17/241; C01F17/224; C01P; C01P2004/00; C01P2004/60; C01P2004/61
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
27 words
A process according to claim 1 wherein said rare earth is selected from the group consisting of lanthanum, samarium, europium, terbium, yttrium and gadolinium and mixtures thereof.
Claim 2
Dependent Claim
12 words
A process according to claim 2 wherein said oxide is gadolinium oxide.
Claim 3
Dependent Claim
12 words
A process according to claim 2 wherein said oxide is yttrium oxide.
Claim 4
Dependent Claim
14 words
A process according to claim 2 wherein said oxide is mixed crystal yttrium-gadolinium oxide.
Claim 5
Dependent Claim
23 words
A process according to claim 2 wherein said oxide contains europium and is suitable for conversion to a europium-activated rare earth oxide phosphor.
Claim 6
Dependent Claim
24 words
A process according to claim 2 wherein said oxalic acid concentration is from about 5 percent by weight to about 30 percent by weight.
Claim 7
Dependent Claim
15 words
A process according to claim 7 wherein said particle size is above about 5 microns.
References Cited (Backward Citations)
US3420861A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-17 | 1975-07-19 | 1976-01-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-17 | 1979-07-19 | 1980-01-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-17 | 1983-07-19 | 1984-01-18 | $7700.00 | Window Closed / Lapsed |