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US5580490A
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Crystallites of cerium/lanthanum/terbium phosphates from insoluble rare earth salts
Assignee: Rhodia Chimie SAS
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Filing: 1994-09-12
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Granted: 1996-12-03
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Expires: 2014-09-12
Abstract
Abstract Needle-shaped solid crystallites of specific LaCeTb phosphates, well suited for the production of green phosphors therefrom, are essentially pure white in color after calcination at 900° C. and have the formula (I): La.sub.x Ce.sub.y Tb.sub.(1-x-y) PO.sub.4 (I) in which x and y are numbers, with x ranging from 0.4 to 0.6 and x+y being greater than 0.8.
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 08:17
CPC Classifications
C; C01; C01F; C01F17/00; C01B; C01B25/00; C01B25/16; C01B25/26; C01B25/45; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7777
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
40 words
Needle-shaped crystallites of a cerium lanthanum terbium phosphate having the formula (I): La.sub.x Ce.sub.y Tb.sub.(1-x-y) PO.sub.4 (I) in which x and y are numbers, with x being in the range of 0.4 to 0.6 and x+y being greater than 0.8.
Claim 2
Dependent Claim
40 words
Needle-shaped crystallites of a cerium lanthanum terbium phosphate having the formula (I): La.sub.x Ce.sub.y Tb.sub.(1-x-y) PO.sub.4 (I) in which x and y are numbers, with x being in the range of 0.4 to 0.6 and x+y being greater than 0.8.
Claim 3
Dependent Claim
27 words
The LaCeTb phosphate crystallites as defined by claim 1, having lengths ranging from 50 nm to 200 nm and widths ranging from 10 nm to 50 nm.
Claim 4
Dependent Claim
16 words
The LaCeTb phosphate crystallites as defined by claim 1, having an essentially pure monoclinic crystalline structure.
Claim 5
Dependent Claim
15 words
A particulate LaCeTb phosphate comprising aggregates of the needle-shaped crystallites as defined by claim 1.
Claim 6
Dependent Claim
22 words
The particulate LaCeTb phosphate as defined by claim 4, said aggregates having a mean diameter ranging from 1 μm to 15 μm.
Claim 7
Dependent Claim
22 words
The particulate LaCeTb phosphate as defined by claim 5, said aggregates having a mean diameter ranging from 2 μm to 10 μm.
Claim 8
Dependent Claim
23 words
The particulate LaCeTb phosphate as defined by claim 4, having a particle size dispersion index I ranging from about 0.5 to about 0.8.
Claim 9
Dependent Claim
23 words
The particulate LaCeTb phosphate as defined by claim 4, exhibiting a lightness, represented by the L * coordinate thereof, of greater than 90.
Claim 10
Dependent Claim
24 words
The particulate LaCeTb phosphate as defined by claim 4, exhibiting a lightness, represented by the L * coordinate thereof, ranging from 95 to 97.
Claim 11
Dependent Claim
23 words
The particulate LaCeTb phosphate as defined by claim 4, exhibiting a lightness, represented by the L * coordinate thereof, of greater than 99.
Claim 12
Dependent Claim
35 words
The particulate LaCeTb phosphate as defined by claim 4, exhibiting a color coordinate a * ranging from about -2 to about -1 and a color coordinate b * ranging from about 5 to about 9.
Claim 13
Dependent Claim
32 words
The particulate LaCeTb phosphate as defined by claim 10, exhibiting a color coordinate a * ranging from -0.7 to -0.1 and a color coordinate b * ranging from 0. 5 to 1.5.
Claim 14
Dependent Claim
22 words
The particulate LaCeTb phosphate as defined by claim 4, after calcination of the phosphate at a temperature of at least 700° C.
Claim 15
Dependent Claim
22 words
The particulate LaCeTb phosphate as defined by claim 4, after calcination of the phosphate at a temperature of at least 900° C.
Claim 16
Dependent Claim
29 words
The particulate LaCeTb phosphate as defined by claim 4, which exhibits luminescence at a wavelength of about 550 nm upon exposure to a light beam of approximately 254 nm.
Claim 17
Dependent Claim
16 words
The particulate LaCeTb phosphate as defined by claim 4, having an essentially pure monoclinic crystalline structure.
Claim 18
Dependent Claim
18 words
The LaCeTb phosphate crystallites as defined by claim 1, further comprising a luminescence promoter or oxidation state stabilizer.
Claim 19
Dependent Claim
8 words
A phosphor from the phosphate of claim 1.
Claim 20
Dependent Claim
48 words
The particulate LaCeTb phosphate as defined by claim 4, wherein after calcination in air, the phosphate exhibits two doublets and the absence of a satellite peak situated at 32.7 eV from the first peak in XPS analysis in the energy range corresponding to the 3d electron of cerium.
Claim 21
Dependent Claim
19 words
A phosphor obtained by calcination of the phosphate of claim 4 at a temperature of at least 600° C.
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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) | 1999-12-03 | 2000-06-03 | 2000-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-12-03 | 2004-06-03 | 2004-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-12-03 | 2008-06-03 | 2008-12-03 | $7700.00 | Window Closed / Lapsed |