US4157981A
Expired / Lapsed
US
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Method of producing a luminescent alkaline earth metal fluorohalide activated by bivalent europium
Assignee: US Philips Corp
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Filing: 1978-04-03
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Granted: 1979-06-12
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Expires: 1998-04-03
Abstract
Abstract Method of preparing a luminescent alkaline earth metal fluorohalide activated by Eu 2+ defined by the formula Me 1-p Eu p FX (Me=Ba, Sr; X=Cl, Br, I; 0.001≦p≦0.20). MeF 2 is suspended in water after which 1 mole of MeX 2 per mole of MeF 2 is dissolved in the suspension. The suspension, which may already contain europium, is evaporated to dryness at 50° C. to 250° C. The obtained product is mixed with the additional required amount of europium in the form of a europium halide and then is subjected to at least one temperature treatment at 600° C. to 1000° C. in a weakly reducing atmosphere. The obtained reaction product is subjected, possibly after being ground, to a final heating at 600° C. to 850° C. in an inert or weakly reducing atmosphere.
Inventors
- 👤 Albert L. N. Stevels
- 👤 Agnes D. M. Schrama-de Pauw
- 👤 Francois Pingault
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:05
CPC Classifications
C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7728; C09K11/7732; C09K11/7733
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
184 words
A method for the preparation of a bivalent europium activated luminescent alkaline earth metal fluorohalide of the formula Me 1-p Eu p FX where Me is at least one alkaline earth metal selected from the group consisting of Ba and Sr, up to 20 mole percent of Me being replaceable by Ca, X is at least one halogen selected from the group consisting of Cl, Br and I and 0.001≦p≦0.20, comprising forming an aqueous suspension of MeF 2 and an equimolar amount of MeX 2 in dissolved form per mole of MeF 2 , evaporating said suspension to dryness at a temperature of 50° C. to 250° C., mixing the resultant MeFX product with p moles of EuX 3 per mole of MeFX product, heating the resultant dried mixture in a weakly reducing atmosphere of nitrogen and a small amount of hydrogen for effectively reducing trivalent europium to bivalent europium, at a temperature of 600° C. to 1000° C., and then, after cooling, heating the resultant bivalent europium activated alkaline earth metal fluorohalide, in an inert atmosphere, at a temperature of 600° C.-850° C.
Claim 2
Independent Claim
184 words
A method for the preparation of a bivalent europium activated luminescent alkaline earth metal fluorohalide of the formula Me 1-p Eu p FX where Me is at least one alkaline earth metal selected from the group consisting of Ba and Sr, up to 20 mole percent of Me being replaceable by Ca, X is at least one halogen selected from the group consisting of Cl, Br and I and 0.001≦p≦0.20, comprising forming an aqueous suspension of MeF 2 and an equimolar amount of MeX 2 in dissolved form per mole of MeF 2 , evaporating said suspension to dryness at a temperature of 50° C. to 250° C., mixing the resultant MeFX product with p moles of EuX 3 per mole of MeFX product, heating the resultant dried mixture in a weakly reducing atmosphere of nitrogen and a small amount of hydrogen for effectively reducing trivalent europium to bivalent europium, at a temperature of 600° C. to 1000° C., and then, after cooling, heating the resultant bivalent europium activated alkaline earth metal fluorohalide, in an inert atmosphere, at a temperature of 600° C.-850° C.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein the dried mixture is heated at a temperature of 800° to 950° C. in an atmosphere of nitrogen containing 0.1 to 1 volume % of hydrogen.
Claim 4
Dependent Claim
22 words
A bivalent europium activated luminescent alkaline earth metal fluorohalide having a substantially reduced afterglow and produced by the method of claim 1.
Claim 5
Dependent Claim
26 words
A method as claimed in claim 1 wherein said bivalent europium activated alkaline earth metal fluorohalide is ground prior to said heating in an inert atmosphere.
Claim 6
Dependent Claim
22 words
Method as claimed in claim 4, characterized in that a fluorohalide defined by the formula Ba 1-p Eu p FCl is prepared.
Claim 7
Dependent Claim
24 words
Method as claimed in claim 5, characterized in that the evaporation to dryness takes place at a temperature of 160° C. to 180° C.
Claim 8
Dependent Claim
32 words
The method of claim 1 wherein said heating of the resultant bivalent europium activated alkaline earth metal flurohalide is carried out in nitrogen at a temperature of 700° C. to 800° C.
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) | 1982-06-11 | 1982-12-11 | 1983-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-06-11 | 1986-12-11 | 1987-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-06-11 | 1990-12-11 | 1991-06-12 | $7700.00 | Window Closed / Lapsed |