Claims
- 1. A method of making a high emission efficiency alkali metal thiogallate phosphor comprising
intimately mixing an alkali metal sulfate having a particle size below about 10 microns coated with an activator with gallium nitrate solution in an amount such that an excess of gallium is present in the final phosphor product, precipitating the activated alkali metal gallium sulfate, and firing in the presence of hydrogen sulfide.
- 2. A method according to claim 1 wherein an excess of 1 to 7% by weight of gallium is present in the phosphor.
- 3. A method of making high emission efficiency thiogallate phosphors comprising
a) forming an aqueous solution of a soluble alkali metal salt; b) adding a sulfate to precipitate an alkali metal sulfate; c) re-suspending the sulfate in water; d) adding 2-5 mol % of the sulfate of a soluble activator salt, e) precipitating the activator salt onto the alkali metal sulfate; f) adding a 1 to 7% excess of a solution of a soluble gallium salt to the precipitate, g) neutralizing the solution to form a precipitate, and h) firing the precipitate in hydrogen sulfide to form the corresponding sulfide phosphor.
- 4. A method according to claim 3 wherein the alkali metal is selected from the group consisting of strontium, calcium and mixtures thereof.
- 5. A method according to claim 4 wherein the soluble salt is a nitrate.
- 6. A method according to claim 3 wherein the activator is selected from the group consisting of europium, praseodymium and cerium.
- 7. A method according to claim 3 wherein step h) is carried out by heating at 800° C. and then at 850° C.
- 8. A method according to claim 3 wherein step h) is carried out by heating at 800° C. and then at 900° C.
- 9. A method according to claim 3 wherein an organic solvent is added to the sulfate solution of step f) prior to firing.
Parent Case Info
[0001] This application claims priority from Provisional application Ser. No. 60/222,678 filed Aug. 2, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
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60222678 |
Aug 2000 |
US |