USRE28592E - Terbium activated rare earth oxyhalide phosphors containing ytterbium for reduced afterglow - Google Patents
Terbium activated rare earth oxyhalide phosphors containing ytterbium for reduced afterglow Download PDFInfo
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- USRE28592E USRE28592E US47127174A USRE28592E US RE28592 E USRE28592 E US RE28592E US 47127174 A US47127174 A US 47127174A US RE28592 E USRE28592 E US RE28592E
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- rare earth
- ytterbium
- afterglow
- phosphors
- terbium
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
- C09K11/7767—Chalcogenides
- C09K11/7769—Oxides
- C09K11/777—Oxyhalogenides
Definitions
- ABSTRACT Phosphors of reduced afterglow having the inclusion of a selected impurity in the phosphors lattice. More specifically, rare earth oxyhalide phosphors of reduced phosphorescence comprising lanthanum and gadolinium oxyhalide phosphors activated with terbium including the selected impurity ytterbium.
- the present invention relates to rare earth oxyhalide phosphors activated with terbium, and particularly, to such rare earth oxyhalide phosphors having reduced afterglow or phosphorescence.
- the rare earth oxyhalides activated with terbium are finding increasing use as phosphors in X-ray intensifier screens and similar radiographic devices, replacing past conventional phosphors of less desirable properties.
- LaOBrzTb has about a 50 percent greater absorption of incident X-rays and about three to four times greater blue emission than the previously used CaWO
- intensifier screens are provided with photographic films which tend to fog if a phosphor is used having an afterglow or long persistent phosphorescence of appreciable intensity. With the use of these long afterglow phosphors, any movement of the film relative to the phosphor screen immediately after exposure will result in blurred images. Attempts to eliminate the problem of blurred images in X-ray intensifier screens have been generally unsuccessful because any reduction in duration and intensity of thephosphor afterglow normally has been at the expense of the overall phosphor efficiency.
- the present invention eliminates the problem of blurred images by providing rare earth oxyhalide phosphors with significantly reduced afterglow without an I appreciable loss in phosphor efficiency.
- the present invention relates to terbium-activated rare earth oxyhalide phosphors having a selected impurity for reducing the phosphors afterglow. More specifically, the present invention relates to rare earth oxyhalide phosphors including ytterbium as an impurity and having the general formula:
- M is an element selected from the group consisting of La and Gd
- X is an element selected from the 5 group consisting of Cl'and Br
- w is from 0.0005 to 0.03 moles per mole of the selected oxyhalide
- y is from 0.00005 to 0.005 moles per mole of the selected oxyhalide.
- the ytterbium impurity addition of the present invention is made by the oxalate precipitation method. This method is outlined below for the preparation of the o.9n15 o.oo2 Yb 0.005] 0.0005.
- lanthanum oxide (2,330g), terbium oxide (5.4g), and ytterbium oxide [(0.0l4lg)] (1.413) are dissolved in a mixture of concentrated nitric acid (3,055ml) and water (ll,6l5ml).
- This mixture is then coprecipitated with 10 percent oxalic acid (40,600ml) to form the oxalates of lanthanum, terbium and ytterbium.
- the oxalates are then fired to effect the chemical conversion of the oxalates to the mixed oxides'of lanthanum, terbium and yt- 40 terbium at 1,000C for 2 hours in open boats.
- the mixed oxides of lanthanum, terbium and ytterbium (2,230g) are blended thoroughly with ammonium bromide (1,440g) and fired 2 hours at 425C in covered boats to chemically form the phosphor, terbiumactivated lanthanum oxybromide containing ytterbium.
- Molten potassium bromide serves as a crystal-growing medium in this firing in order to produce well-crystallized terbiumactivated lanthanum oxybromide containing ytterbium. The material is then washed to remove the potassium bromide. It is subsequently dried in an oven for 2 hours at C, and then sifted through 325 mesh.
- a rare earth oxyhalide phosphor of reduced afterglow having the general formula:
- M is an element selected from the group consisting of La and Gd;
- a rare earth oxyhalide phosphor of reduced afterglow according to claim 1 wherein:
- M La X is Br w is 0.002 y is 0.0005.
Abstract
Phosphors of reduced afterglow having the inclusion of a selected impurity in the phosphors lattice. More specifically, rare earth oxyhalide phosphors of reduced phosphorescence comprising lanthanum and gadolinium oxyhalide phosphors activated with terbium including the selected impurity ytterbium.
Description
United States Patent 191 Rabatin et al.
[111 E Re. 28,592
[ 5] Reissued Oct. 28, 1975 TERBIUM ACTIVATED RARE EARTH OXYHALIDE PHOSPHORS CONTAINING YTTERBIUM FOR REDUCED AFTERGLOW Reissue of:
[64] Patent No.: 3,666,676
Issued: May 30, 1972 Appl. No.: 100,448
Filed: Dec. 21, 1970 [52] US. Cl. 252/30l.4 H [51] Int. Cl. C09K 11/24; C09K l 1/46 [58] Field of Search 252/30l.4 H
[56] References Cited UNITED STATES PATENTS 3,546,128 l2/l970 Rabatin 252/30L4 H 3,607,770 9/l97l Rabatin 252/30l.4 H
OTHER PUBLICATIONS Blasse et al., Investigation of Tb Activated Phosphors" Philips Research Reports 22(5), 1967, pp. 481-504.
Primary ExaminerJack Cooper Attorney, Agent, or Firm.lohn F. McDevitt; Henry P. Truesdell; Frank L. Neuhauser [57] ABSTRACT Phosphors of reduced afterglow having the inclusion of a selected impurity in the phosphors lattice. More specifically, rare earth oxyhalide phosphors of reduced phosphorescence comprising lanthanum and gadolinium oxyhalide phosphors activated with terbium including the selected impurity ytterbium.
2 Claims, N0 Drawings 1 TERBIUM ACTIVATED RARE EARTH OXYI-IALIDE PI-IOSPHORS CONTAINING YTTERBIUM FOR REDUCED AFTERGLOW Matter enclosed in heavy brackets I: appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.
BACKGROUND OF THE INVENTION The present invention relates to rare earth oxyhalide phosphors activated with terbium, and particularly, to such rare earth oxyhalide phosphors having reduced afterglow or phosphorescence.
The rare earth oxyhalides activated with terbium are finding increasing use as phosphors in X-ray intensifier screens and similar radiographic devices, replacing past conventional phosphors of less desirable properties. For example, LaOBrzTb has about a 50 percent greater absorption of incident X-rays and about three to four times greater blue emission than the previously used CaWO Currently intensifier screens are provided with photographic films which tend to fog if a phosphor is used having an afterglow or long persistent phosphorescence of appreciable intensity. With the use of these long afterglow phosphors, any movement of the film relative to the phosphor screen immediately after exposure will result in blurred images. Attempts to eliminate the problem of blurred images in X-ray intensifier screens have been generally unsuccessful because any reduction in duration and intensity of thephosphor afterglow normally has been at the expense of the overall phosphor efficiency.
The present invention eliminates the problem of blurred images by providing rare earth oxyhalide phosphors with significantly reduced afterglow without an I appreciable loss in phosphor efficiency.
Accordingly, it is an object of the present invention to provide a rare earth oxyhalide phosphor activated with terbium having a reduced afterflow.
It is a further object of the present invention to provide a terbium-activated lanthanum or gadolinium oxychloride or oxybromide phosphor including a selected impurity to achieve reduced afterglow.
Further objects and attendant advantages will be apparent from the following summary and detailed description.
SUMMARY OF THE INVENTION The present invention relates to terbium-activated rare earth oxyhalide phosphors having a selected impurity for reducing the phosphors afterglow. More specifically, the present invention relates to rare earth oxyhalide phosphors including ytterbium as an impurity and having the general formula:
wherein M is an element selected from the group consisting of La and Gd; X is an element selected from the 5 group consisting of Cl'and Br; and w is from 0.0005 to 0.03 moles per mole of the selected oxyhalide; and y is from 0.00005 to 0.005 moles per mole of the selected oxyhalide.
o DETAILED DESCRIPTION OF THE INVENTION lected impurity, ytterbium, is incorporated in the phosphor lattice in order to reduce the afterglow of the phosphor without any appreciable decrease in the overall phosphor efficiency.
The following are a few of the rare earth oxyhalide phosphors included in this invention:
The ytterbium impurity addition of the present invention is made by the oxalate precipitation method. This method is outlined below for the preparation of the o.9n15 o.oo2 Yb 0.005] 0.0005.
In this first step of the preparation, lanthanum oxide (2,330g), terbium oxide (5.4g), and ytterbium oxide [(0.0l4lg)] (1.413) are dissolved in a mixture of concentrated nitric acid (3,055ml) and water (ll,6l5ml). This mixture is then coprecipitated with 10 percent oxalic acid (40,600ml) to form the oxalates of lanthanum, terbium and ytterbium. The oxalates are then fired to effect the chemical conversion of the oxalates to the mixed oxides'of lanthanum, terbium and yt- 40 terbium at 1,000C for 2 hours in open boats.
The mixed oxides of lanthanum, terbium and ytterbium (2,230g) are blended thoroughly with ammonium bromide (1,440g) and fired 2 hours at 425C in covered boats to chemically form the phosphor, terbiumactivated lanthanum oxybromide containing ytterbium.
num oxybromide containing ytterbium. Molten potassium bromide serves as a crystal-growing medium in this firing in order to produce well-crystallized terbiumactivated lanthanum oxybromide containing ytterbium. The material is then washed to remove the potassium bromide. It is subsequently dried in an oven for 2 hours at C, and then sifted through 325 mesh.
The effect. of ytterbium on the reduction of afterglow in LaOBrzTb is shown in Table I.
TABLE I The Effect of Ytterbium on the Reduction Of Afterglow Properties of LaOBrzTb TABLE l-continued The Effect of Ytterbium on the Reduction of Afterglow Properties of LaOBnTb,
Relative Moles of Phosphor Phosphorescence Intensity Ytterbium Brightness In Volts After Indicated Per Mole Under X-ray Time in Sec. of Phosphor Excitation 0.01 l 9 52 TABLE I] per cm and at a sensitivity of 0.05 volts per cm. The phosphor was exposed to the X-rays for 10 seconds after which the X-rays were turned off and the decay measurements were made.
What is claimed as new and desired to be secured by Letters Patent of the United States is:
l. A rare earth oxyhalide phosphor of reduced afterglow having the general formula:
wherein M is an element selected from the group consisting of La and Gd;
Effect of Ytterbium on the Afterglow Intensities Of Various Rare Earth Oxyhalides Activated with Terbium Moles of Phopsphorescence Intensity Ytterbium In Volts After Indicated Phosphor Per Mole Time in Sec. Composition of Phosphor l 3 52 LaOCl:T 0 0000 0 .0000 .28 .18 .12 .02 g 5] 9 .0002 .23 .09 .04 .00 .0010 .17 .03 .01 .00 GdOBrzTb 00000 0 .0000 .31 .25 .18 .00 5] .0010 .24 .02 .00 .00 GdOClzT 0 0000 .0000 .37 .15 .10 .01 l); Show .0010 .25 .00 .00 .00
MEASUREMENTS OF PHOSPHORESCENCE DECAY All decay measurements were made with an X-ray generator set at 90KV peak and at a milliampere setting to give volt constant output as read on an image storing oscilloscope when an 5-1] photomultiplier was set at 800 volts. 0.8 gram of phosphor was pressed into a plastic sample holder of mm diameter. The sample was placed about 3 inches above the generator target. The photomultiplier was set about 4 inches above the sample holder. The decay curves were recorded on the oscilloscope face with the photomultiplier set at 1400 volts and the oscilloscope set at a sweep of 5 seconds X is an element selected from the group consisting of Cl and Br; w is from 0.0005 to 0.03 moles per mole of the selected oxyhalide; and y is from 0.00005 to 0.005 moles per mole of the selected oxyhalide. 2. A rare earth oxyhalide phosphor of reduced afterglow according to claim 1 wherein:
M is La X is Br w is 0.002 y is 0.0005.
Claims (2)
1. A RARE EARTH OXYHALIDE PHOSPHOR OF REDUCED AFTERGLOW HAVING THE GENERAL FORMULA:
2. A rare earth oxyhalide phosphor of reduced afterglow according to claim 1 wherein: M is La X is Br w is 0.002 y is 0.0005.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47127174 USRE28592E (en) | 1970-12-21 | 1974-05-20 | Terbium activated rare earth oxyhalide phosphors containing ytterbium for reduced afterglow |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10044870A | 1970-12-21 | 1970-12-21 | |
| US47127174 USRE28592E (en) | 1970-12-21 | 1974-05-20 | Terbium activated rare earth oxyhalide phosphors containing ytterbium for reduced afterglow |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USRE28592E true USRE28592E (en) | 1975-10-28 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US47127174 Expired USRE28592E (en) | 1970-12-21 | 1974-05-20 | Terbium activated rare earth oxyhalide phosphors containing ytterbium for reduced afterglow |
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| US (1) | USRE28592E (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4054798A (en) | 1975-11-14 | 1977-10-18 | Tokyo Shibaura Electric Co., Ltd. | X-ray conversion screens |
| US4068129A (en) | 1976-12-13 | 1978-01-10 | General Electric Company | Bismuth activated rare earth oxybromide phosphors and X-ray image converters utilizing said phosphors |
| US4488983A (en) | 1983-04-22 | 1984-12-18 | E. I. Du Pont De Nemours And Company | Preparation of lanthanum bismuth oxychloride phosphors |
| US4532070A (en) | 1983-04-08 | 1985-07-30 | General Electric Company | Process for the preparation of rare earth oxyhalide phosphor |
| US4571305A (en) | 1983-04-08 | 1986-02-18 | General Electric Company | Process for the preparation of rare earth oxyhalide phosphor |
| US4603259A (en) | 1983-04-08 | 1986-07-29 | General Electric Company | X-ray image converter devices using rare earth oxyhalide phosphors |
| US20160061962A9 (en) * | 2008-08-07 | 2016-03-03 | Cornelis Ronda | Scintillating material and related spectral filter |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3546128A (en) * | 1968-10-23 | 1970-12-08 | Gen Electric | Lanthanum and gadolinium oxybromide luminescent materials activated with erbium |
| US3607770A (en) * | 1968-10-23 | 1971-09-21 | Gen Electric | Gaseous reaction process for the production of rare earth oxyhalide and oxide luminescent materials |
-
1974
- 1974-05-20 US US47127174 patent/USRE28592E/en not_active Expired
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3546128A (en) * | 1968-10-23 | 1970-12-08 | Gen Electric | Lanthanum and gadolinium oxybromide luminescent materials activated with erbium |
| US3607770A (en) * | 1968-10-23 | 1971-09-21 | Gen Electric | Gaseous reaction process for the production of rare earth oxyhalide and oxide luminescent materials |
Non-Patent Citations (1)
| Title |
|---|
| Blasse et al., "Investigation of Tb.sup.+.sup.3 Activated Phosphors" Philips Research Reports 22(S), 1967, pp. 481-504 * |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4054798A (en) | 1975-11-14 | 1977-10-18 | Tokyo Shibaura Electric Co., Ltd. | X-ray conversion screens |
| US4068129A (en) | 1976-12-13 | 1978-01-10 | General Electric Company | Bismuth activated rare earth oxybromide phosphors and X-ray image converters utilizing said phosphors |
| US4532070A (en) | 1983-04-08 | 1985-07-30 | General Electric Company | Process for the preparation of rare earth oxyhalide phosphor |
| US4571305A (en) | 1983-04-08 | 1986-02-18 | General Electric Company | Process for the preparation of rare earth oxyhalide phosphor |
| US4603259A (en) | 1983-04-08 | 1986-07-29 | General Electric Company | X-ray image converter devices using rare earth oxyhalide phosphors |
| US4488983A (en) | 1983-04-22 | 1984-12-18 | E. I. Du Pont De Nemours And Company | Preparation of lanthanum bismuth oxychloride phosphors |
| US20160061962A9 (en) * | 2008-08-07 | 2016-03-03 | Cornelis Ronda | Scintillating material and related spectral filter |
| US9638807B2 (en) * | 2008-08-07 | 2017-05-02 | Koninklijke Philips N.V. | Scintillating material and related spectral filter |
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