Coated phosphors and light emitting devices including the same
View Patent ↗Provided according to embodiments of the invention are method of coating a phosphor that include contacting the phosphor with a sol comprising at least one of silica, alumina, borate and a precursor thereof, to form a coating on the phosphor; and heating the phosphor. Also provided are phosphors that are coated with alumina, silica and/or borate, and light emitting devices that include such phosphors.
1. A method of coating a phosphor comprising:
(a) contacting a nitride phosphor with a sol comprising: at least one of silica, alumina, borate and a precursor thereof, and an acid catalyst; and
(b) heating the phosphor at a temperature in a range of 200° C. to 600° C., thereby forming a coated phosphor,
wherein the sol comprises at least one of colloidal silica and colloidal alumina, and
wherein the sol does not include a precursor of silica, a precursor of alumina, or a precursor of borate.
2. The method of claim 1 , wherein the sol further comprises a solvent.
3. The method of claim 2 , wherein the solvent comprises at least one solvent selected from the group consisting of water, methanol, ethanol, propanol, butanol, 2-ethoxyethanol, formamide, dimethylformamide, dioxane and tetrahydrofuran.
4. The method of claim 1 , wherein the acid catalyst comprises hydrochloric acid.
5. The method of claim 1 , wherein the acid catalyst comprises acetic acid.
6. The method of claim 1 , wherein the sol comprises a tetraalkylorthosilicate.
7. The method of claim 1 , wherein the sol comprises a trialkylborate.
8. The method of claim 1 , wherein the sol comprises alumina and/or aluminum sulfate.
9. The method of claim 1 , wherein the phosphor is stirred in the sol for a time in a range of 0.1 to 40 hours.
10. A coated phosphor comprising:
a nitride phosphor in particulate form coated with alumina, silica and/or borate, wherein the phosphor has a du′v′ of less than 0.0015 after 840 hours at 85° C. and 85% relative humidity.
11. The coated phosphor of claim 10 , wherein the phosphor has an average particle size in a range of 2 to 25 microns.
12. The coated phosphor of claim 10 , further comprising a green and/or yellow phosphor.
13. The method of claim 1 , wherein the nitride phosphor is reacted with the sol for a time in a range of from 16 to 24 hours.
14. The method of claim 1 , wherein, prior to contacting the nitride phosphor with the sol, the sol is reacted for a time in a range of 24 to 32 hours.
15. The method of claim 1 , further comprising heating the coated phosphor at 200° C. for 2-6 hours.