US3669897A
Expired / Lapsed
US
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Divalent europium activated alkaline earth metal sulfates and method of preparation
Assignee: Philips North America LLC
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Filing: 1969-11-14
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Granted: 1972-06-13
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Expires: 1989-11-14
Abstract
Abstract Divalent europium activated alkaline earth metal sulfates wherein the metal is at least one of calcium, barium, or strontium, and europium is present in atom percent of the alkaline-earth metal of from about 0.4 to 7. The compositions emit very efficiently in the near-ultraviolet upon short wavelength ultraviolet excitation. A preferred mode of preparing the compositions is set forth whereby the composition is precipitated from solution.
Inventors
- 👤 Anselm Wachtel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:08
CPC Classifications
C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7728; C09K11/7741
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
28 words
The method as specified in claim 1, wherein the mixture is fired at from about 750* to 1,300* C for at least one-half hour in an inert atmosphere.
Claim 2
Independent Claim
114 words
The method of preparing the luminescent composition Ca(1 x)SO4:Eux 2, wherein x is from 0.004 to 0.07, which method comprises; a. adding a predetermined amount of sulfate radical containing solution to a solution containing predetermined amounts of calcium ions and divalent europium ions, with the ratio of sulfate radicals to total metal ions being at least one, and maintaining the resulting mixture at a temperature of from about 70* C to the boiling point of the resulting mixture, whereby europium activated calcium sulfate is precipitated; b. separating the resulting precipitate from the mixture; c. mixing up to about 3 mol percent of calcium chloride as flux with the precipitate; and d. firing the mixture.
Claim 3
Dependent Claim
28 words
The method as specified in claim 3, wherein the mixture is fired at from about 750* to 900* C for at least 1 hour in an inert atmosphere.
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) | 1975-06-13 | 1975-12-13 | 1976-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-13 | 1979-12-13 | 1980-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-13 | 1983-12-13 | 1984-06-13 | $7700.00 | Window Closed / Lapsed |