US3878119A
Expired / Lapsed
US
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Preparation of rare-earth oxysulfide phosphors
Assignee: General Electric Co
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Filing: 1972-12-26
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Granted: 1975-04-15
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Expires: 1992-12-26
Abstract
Abstract Rare-earth oxysulfide luminescent materials are recrystallized by liquid phase sintering in a vitreous flux. The vitreous flux composition is the heat reaction product of one or more alkali metal ions selected from the group consisting of lithium, sodium, and potassium with an oxide selected from the group consisting of SiO2, GeO2, and B2O3, including mixtures thereof. Various methods of preparation can be used which includes firing a preformed vitreous flux with the oxysulfide phosphor crystals as well as converting a rare-earth oxide mixture with a sulfurizing agent to oxysulfide phosphor crystals in the presence of source materials for the vitreous flux and thereafter recrystallizing the phosphor crystals in the vitreous flux which is formed in situ.
Inventors
- 👤 Dilip K Nath
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 20:52
CPC Classifications
C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7767; C09K11/7769; C09K11/7771; C09K11/7783; C09K11/7784; C09K11/7787; C09K11/7789
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
18 words
A METHOD OF PREPARING A LUMINESCENT MATERIAL WHICH COMPRISES: A. BLENDING PHOSPHOR CRYSTALS HAVING THE FOLLOWING CHEMICAL COMPOSITION:
Claim 2
Independent Claim
18 words
A METHOD OF PREPARING A LUMINESCENT MATERIAL WHICH COMPRISES: A. BLENDING PHOSPHOR CRYSTALS HAVING THE FOLLOWING CHEMICAL COMPOSITION:
Claim 3
Dependent Claim
47 words
A method as in claim 1 wherein the vitreous flux is preformed by heating the flux composition at a temperature of at least 500*C for a sufficient time period to form a heat reaction product containing vitreous phase and blending said vitreous flux with the phosphor crystals.
Claim 4
Independent Claim
230 words
A method of preparing a luminescent material which comprises: a. heating a rare-earth oxide mixture with a sulfurizing agent to an elevated temperature of at least about 700*C until oxysulfide phosphor crystals are formed, said phosphor crystals having the following chemical composition: Ln(2 x)Ln''xO2S wherein Ln is one or more of Y, Gd, La and Lu, and Ln'' is one or more of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb, and Tm, and x is from 0.0002 to 0.2, b. cooling the phosphor crystals and blending said crystals with a flux composition selected from a preformed vitreous flux and source materials which form said vitreous flux in situ; said flux composition consisting essentially of an alkali metal oxide selected from the group consisting of lithium, sodium, and potassium oxides together with an oxide selected from the group consisting of SiO2, GeO2, and B2O3 including mixtures thereof, at a molar ratio between the alkali metal oxide and each of said SiO2, GeO2, and B2O3 in the flux composition which ranges from 0.5 to 1.0 and 1.0 to 0.5, wherein the weight ratio of the flux composition is from 0.1 to 7 weight percent of the luminescent material, and c. firing the blended product in the approximate temperature range 1000*C-1350*C in an inert atmosphere for a sufficient time period to recrystallize the phosphor crystals having uniformly dispersed therein the vitreous flux.
Claim 5
Independent Claim
230 words
A method of preparing a luminescent material which comprises: a. heating a rare-earth oxide mixture with a sulfurizing agent to an elevated temperature of at least about 700*C until oxysulfide phosphor crystals are formed, said phosphor crystals having the following chemical composition: Ln(2 x)Ln''xO2S wherein Ln is one or more of Y, Gd, La and Lu, and Ln'' is one or more of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb, and Tm, and x is from 0.0002 to 0.2, b. cooling the phosphor crystals and blending said crystals with a flux composition selected from a preformed vitreous flux and source materials which form said vitreous flux in situ; said flux composition consisting essentially of an alkali metal oxide selected from the group consisting of lithium, sodium, and potassium oxides together with an oxide selected from the group consisting of SiO2, GeO2, and B2O3 including mixtures thereof, at a molar ratio between the alkali metal oxide and each of said SiO2, GeO2, and B2O3 in the flux composition which ranges from 0.5 to 1.0 and 1.0 to 0.5, wherein the weight ratio of the flux composition is from 0.1 to 7 weight percent of the luminescent material, and c. firing the blended product in the approximate temperature range 1000*C-1350*C in an inert atmosphere for a sufficient time period to recrystallize the phosphor crystals having uniformly dispersed therein the vitreous flux.
Claim 6
Dependent Claim
38 words
A method as in claim 3 wherein the vitreous flux is preformed by heating the flux composition at a temperature of at least 500*C for a sufficient time period to form a heat reaction product containing vitreous phase.
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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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |