Patent US1977133A successfully refreshed from Google Patents.
US4032471A
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Process for preparing yttrium oxide and rare earth metal oxide phosphors
Assignee: Eastman Kodak Co
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Filing: 1976-02-11
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Granted: 1977-06-28
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Expires: 1996-02-11
Abstract
Abstract Phosphors which have a host matrix of yttrium oxide or a rare earth metal oxide and are activated by one or more rare earth metal activators are prepared by heating a mixture of salts of the host and activator metals (preferably this mixture is formed by co-precipitating the salts of the host and activator metals) at an elevated temperature in an oxygen-containing atmosphere to form the oxide phosphor, and subsequently heating the phosphor at an elevated temperature in a non-oxidizing atmosphere, which is free of halogenating agents, chalcogenating agents, or fluxes. The step of heating in a non-oxidizing atmosphere brings about a substantial increase in the X-ray speed of the phosphor, improves the stability of the phosphor to light, and increases the reflectance of the phosphor in the visible region of the spectrum. Phosphors prepared by use of this process are useful in the manufacture of X-ray intensifying screens.
Inventors
- 👤 George W. Luckey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:35
CPC Classifications
C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7767; C09K11/7769
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
123 words
A process of preparing a phosphor having improved x-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a hydrogen-containing mildly reducing atmosphere at an elevated temperature and for a period of time which are sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 2
Dependent Claim
123 words
A process of preparing a phosphor having improved x-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a hydrogen-containing mildly reducing atmosphere at an elevated temperature and for a period of time which are sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 3
Dependent Claim
14 words
A process as described in claim 1 wherein said phosphor is europium-activated gadolinium oxide.
Claim 4
Dependent Claim
14 words
A process as described in claim 1 wherein said phosphor is terbium-activated gadolinium oxide.
Claim 5
Dependent Claim
14 words
A process as described in claim 1 wherein said phosphor is dysprosium-activated gadolinium oxide.
Claim 6
Dependent Claim
14 words
A process as described in claim 1 wherein said phosphor is terbium-activated yttrium oxide.
Claim 7
Dependent Claim
14 words
A process as described in claim 1 wherein said phosphor is gadolinium-activated yttrium oxide.
Claim 8
Dependent Claim
22 words
A process as described in claim 1 wherein said reducing atmosphere consists essentially of a mixture of hydrogen and an inert gas.
Claim 9
Dependent Claim
25 words
A process as described in claim 1 wherein said reducing atmosphere consists essentially of an inert gas, water vapor, carbon monoxide, hydrogen, and carbon dioxide.
Claim 10
Dependent Claim
28 words
A process as described in claim 1 wherein said reducing atmosphere is provided by heating the oxide phosphor in the presence of carbon, inert gas, and water vapor.
Claim 11
Dependent Claim
37 words
A process as described in claim 9 wherein the phosphor is heated in said reducing atmosphere for a period of about 2 to about 4 hours at a temperature of about 800° C. to about 1000° C.
Claim 12
Dependent Claim
145 words
A process of preparing a phosphor having improved X-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a mildly reducing atmosphere, comprising from about 5% to about 35% by volume hydrogen and from about 65% to about 95% by volume of an inert gas, at an elevated temperature and for a period of time which are sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 13
Dependent Claim
145 words
A process of preparing a phosphor having improved X-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a mildly reducing atmosphere, comprising from about 5% to about 35% by volume hydrogen and from about 65% to about 95% by volume of an inert gas, at an elevated temperature and for a period of time which are sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 14
Dependent Claim
49 words
A process as described in claim 11 wherein the step of subsequently heating the phosphor in an atmosphere of hydrogen and an inert gas is for a period of about 2 hours to about 4 hours and is at a temperature of about 450° C. to about 600° C.
Claim 15
Dependent Claim
143 words
A process of preparing a phosphor having improved X-ray speed of the formula Ln.sub.(2 -x ) Z x O 3 , wherein Ln is selected from the group consisting of yttrium, gadolinium, and lanthanum, Z is different from Ln and is selected from the group consisting of europium, terbium, gadolinium, and dysprosium, and x is between 0.0002 and 0.2, comprising: heating a mixture of salts of Ln and Z in an oxygen-containing atmosphere to form the phosphor; and in a subsequent heating step, heating said phosphor in an atmosphere of hydrogen and an inert gas for a period of about 2 hours to about 4 hours at a temperature of about 450° C. to about 600° C., sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 16
Dependent Claim
143 words
A process of preparing a phosphor having improved X-ray speed of the formula Ln.sub.(2 -x ) Z x O 3 , wherein Ln is selected from the group consisting of yttrium, gadolinium, and lanthanum, Z is different from Ln and is selected from the group consisting of europium, terbium, gadolinium, and dysprosium, and x is between 0.0002 and 0.2, comprising: heating a mixture of salts of Ln and Z in an oxygen-containing atmosphere to form the phosphor; and in a subsequent heating step, heating said phosphor in an atmosphere of hydrogen and an inert gas for a period of about 2 hours to about 4 hours at a temperature of about 450° C. to about 600° C., sufficient to effect an increase in the X-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 17
Dependent Claim
135 words
A process of preparing a phosphor having improved x-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a hydrogen-containing mildly reducing atmosphere at a temperature of from about 400° C. to about 1400° C. for a period of time of about 0.5 to about 8.0 hours, sufficient to effect an increase in the x-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
Claim 18
Dependent Claim
135 words
A process of preparing a phosphor having improved x-ray speed which consists essentially of an oxide of an element selected from the group consisting of yttrium, gadolinium, and lanthanum, activated by at least one different rare earth metal activator selected from the group consisting of europium, terbium, gadolinium, and dysprosium, comprising: heating a mixture of salts of said element and said activator in an oxygen-containing atmosphere to form said phosphor; and in a subsequent heating step heating said phosphor in a hydrogen-containing mildly reducing atmosphere at a temperature of from about 400° C. to about 1400° C. for a period of time of about 0.5 to about 8.0 hours, sufficient to effect an increase in the x-ray speed of said phosphor, compared to the speed without such subsequent heating step, of at least about 15%.
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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) | 1980-06-27 | 1980-12-27 | 1981-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-27 | 1984-12-27 | 1985-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-27 | 1988-12-27 | 1989-06-28 | $7700.00 | Window Closed / Lapsed |