Claims
- 1. A process for producing a luminescent phosphor composition consisting essentially of lanthanum cerium aluminate phosphor represented by the formula La.sub.1-x Al.sub.y O.sub.(3/2)(y+1) wherein 0.10<x<1.0 and 11.0.ltoreq.y.ltoreq.12.5 and further characterized by predominantly blue peak emission, comprising the following steps in the sequence set forth:
- a. dissolving lanthanum (III) oxide and cerium (III) nitrate hexahydrate in predetermined proportions as desired in said phosphor composition in hot acid to form a solution;
- b. diluting the solution of step (a) with distilled water;
- c. heating the diluted solution of step (b) to a temperature of about 90.degree. C.;
- d. adding .gamma.-aluminum oxide in a predetermined proportion as desired in said phosphor composition to the heated solution of step (c) to form a suspension;
- e. adding oxalic acid to the suspension of step (d)in an amount at least sufficient to fully precipitate lanthanum (III) and cerium (III) as oxalates;
- f. allowing the suspension of step (e) containing said oxalic acid to stand for a period of time sufficient for a precipitate containing lanthanum, cerium and aluminum in a ratio desired in said phosphor composition to form;
- g. drying the precipitate of step (f) at a temperature of about 140.degree. C.;
- h. pulverizing the dried precipitate of step (g);
- i. firing the pulverized dried precipitate of step (h) in a reducing atmosphere at a temperature of about 1600.degree. to about 1800.degree. C. for about 3 to about 4 hours; and
- j. pulverizing the fired product of step (i).
- 2. The process of claim 1 wherein said reducing atmosphere is hydrogen.
- 3. The process of claim 1 wherein said reducing atmosphere consists of a mixture of at least 5 volume percent hydrogen and the balance an inert gas.
- 4. A process for preparing a luminescent material represented by the formula La.sub.1-x Ce.sub.x Al.sub.y O.sub.(3/2)(y+1) wherein 0.10<x<1.0 and 11.0.ltoreq.y.ltoreq.12.5 and further characterized by predominantly blue peak emission, comprising the following steps in the sequence set forth:
- a. dissolving lanthanum (III) oxide and cerium (III) nitrate hexahydrate in predetermined proportions as desired in said luminescent material in hot acid to form a solution;
- b. diluting the solution of step (a) with distilled water;
- c. adding .gamma.-aluminum oxide in a predetermined proportion as desired in said luminescent material to the diluted solution of step (b) to form a suspension
- d. adding ammonium carbonate until the suspension of step (c) is slightly basic so that lanthanum and cerium precipitate as carbonates;
- e. allowing the suspension of step (d) to stand for a period of time sufficient for a precipitate containing lanthanum, cerium and aluminum in a ratio desired in said luminescent material--has to form;
- f. drying the precipitate at a temperature of about 140.degree. C.;
- g. pulverizing the dried precipitate of step (f);
- h. firing the pulverized dried precipitate of step (g) in a reducing atmosphere at a temperature of about 1600.degree. C. to about 1800.degree. C. for a period of time of about three hours; and
- i. pulverizing the fired product of step (h).
- 5. The process of claim 4 wherein said reducing atmosphere is hydrogen.
- 6. The process of claim 4 wherein said reducing atmosphere consists of a mixture of at least 5 volume percent hydrogen and the balance an inert gas.
Parent Case Info
This is a divisional of co-pending application Ser. No. 133,100 filed on Dec. 14, 1987, which is a divisional of co-pending application Ser. No. 560,296 filed on Dec. 12, 1983.
US Referenced Citations (6)
Foreign Referenced Citations (2)
Number |
Date |
Country |
47-12321 |
Apr 1972 |
JPX |
49-123992 |
Nov 1974 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Verstegen et al., "J. of Lumin.", 6 (1973) pp. 425-431. |
Divisions (2)
|
Number |
Date |
Country |
Parent |
133100 |
Dec 1987 |
|
Parent |
560296 |
Dec 1983 |
|