US5340556A
Expired / Lapsed
US
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Cerium/lanthanum/terbium mixed phosphates
Assignee: Rhodia Chimie SAS
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Filing: 1992-02-04
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Granted: 1994-08-23
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Expires: 2012-02-04
Abstract
Abstract Novel cerium/lanthanum/terbium (LaCeTb) mixed phosphates, especially useful in luminescence for the production of green phosphors, have the formula (I): LaxCeyTb1-x-yPO4 in which x ranges from 0.4 to 0.6 and x+y is greater than 0.8, display a lightness (L*) of greater than 98% after calcination at a temperature above 700 DEG C. in air, and the cerium (IV) and/or terbium (IV) contents of which are very low, even after calcination in air at a temperature above 500 DEG C.
Inventors
- 👤 Marie-Pierre Collin
- 👤 Denis Huguenin
- 👤 Anne-Marie Le Govic
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:47
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/26; C01B25/45; C01B25/14; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7777
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
141 words
A process for the preparation of a cerium lanthanum terbium mixed phosphate having the formula (I): La.sub.x Ce.sub.y Tb.sub.1-x-y PO.sub.4 (I) in which x ranges from 0.4 to 0.6 and x+y is greater than 0.8, and having a lightness (L*), measured by colorimetry, of greater than 98% after calcination at a temperature above 700° C. in air, the process comprising mixing a solution of soluble lanthanum, cerium and terbium salts with phosphate ions, while controlling the pH of such medium of precipitation at a value above 2, to thereby precipitate a mixed phosphate therefrom, maintaining the precipitate in the precipitation medium for a period of time ranging from 15 min to 10 hours after completion of the mixing when the value of the pH of precipitation ranges from 2 to 6, and then filtering off, washing, and optionally drying said precipitate.
Claim 2
Dependent Claim
141 words
A process for the preparation of a cerium lanthanum terbium mixed phosphate having the formula (I): La.sub.x Ce.sub.y Tb.sub.1-x-y PO.sub.4 (I) in which x ranges from 0.4 to 0.6 and x+y is greater than 0.8, and having a lightness (L*), measured by colorimetry, of greater than 98% after calcination at a temperature above 700° C. in air, the process comprising mixing a solution of soluble lanthanum, cerium and terbium salts with phosphate ions, while controlling the pH of such medium of precipitation at a value above 2, to thereby precipitate a mixed phosphate therefrom, maintaining the precipitate in the precipitation medium for a period of time ranging from 15 min to 10 hours after completion of the mixing when the value of the pH of precipitation ranges from 2 to 6, and then filtering off, washing, and optionally drying said precipitate.
Claim 3
Dependent Claim
46 words
The process as defined by claim 1, comprising controlling the pH of the medium of precipitation at a value above 6, and maintaining such pH of the precipitation medium for a period of time ranging from 15 min to 10 hours after completion of the mixing.
Claim 4
Dependent Claim
18 words
The process as defined by claim 1, comprising calcining the recovered precipitate at a temperature above 500° C.
Claim 5
Dependent Claim
15 words
The process as defined by claim 3, comprising conducting said calcination in a reducing atmosphere.
Claim 6
Dependent Claim
15 words
The process as defined by claim 3, comprising conducting said calcination in a nonreducing atmosphere.
Claim 7
Dependent Claim
21 words
The process as defined by claim 1, comprising controlling the pH of the precipitation medium by adding a basic compound thereto.
Claim 8
Dependent Claim
26 words
The process as defined by claim 6, comprising simultaneously adding the phosphate ions and the basic compound to the solution of the soluble rare earth salts.
Claim 9
Dependent Claim
29 words
The process as defined by claim 6, comprising adding the solution of soluble rare earth salts to the solution containing phosphate ions, and simultaneously adding the basic compound thereto.
Claim 10
Dependent Claim
15 words
The process as defined by claim 1, said phosphate ions comprising an ammonium phosphate solution.
Claim 11
Dependent Claim
16 words
The process as defined by claim 9, said ammonium phosphate comprising diammonium phosphate or monoammonium phosphate.
Claim 12
Dependent Claim
13 words
The process as defined by claim 1, said phosphate ions comprising phosphoric acid.
Claim 13
Dependent Claim
14 words
The process as defined by claim 6, said basic compound comprising an ammonium hydroxide.
Claim 14
Dependent Claim
28 words
The process as defined by claim 1, wherein the concentration of rare earths, expressed as rare earth oxide, in said solution ranges from 0.01 mol/l to 2 mol/l.
Claim 15
Dependent Claim
21 words
The process as defined by claim 1, said soluble rare earth salt comprising a rare earth nitrate, chloride, acetate or carboxylate.
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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) | 1997-08-22 | 1998-02-21 | 1998-08-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-22 | 2002-02-21 | 2002-08-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-22 | 2006-02-21 | 2006-08-23 | $7700.00 | Window Closed / Lapsed |