UVC-emitting Sr(Al,Mg)
View Patent ↗The UVC emission of a Sr(Al,Mg) 12 O 19 :Pr is improved by providing an excess of magnesium relative to the molar amount praseodymium In particular, the UVC-emitting phosphor has a composition represented by the formula Sr 1-x Pr x Al 12-y Mg y O 19 wherein y>x. The phosphor is excited by vacuum ultraviolet radiation and may be used to create a mercury-free germicidal lamp.
1. A UVC-emitting phosphor having a composition represented by the formula Sr 1-x Pr x Al 12-y Mg y O 19 wherein 0.01≦x≦0.1, 0.02≦y ≦0.15 and y>x.
2. The phosphor of claim 1 wherein 1<y/x≦3.
3. The phosphor of claim 1 wherein 0.03≦x≦0.07, 0.06≦y≦0.1 and 1.1≦y/x≦2.7.
4. The phosphor of claim 1 wherein 0.04≦x≦0.07, 0.06≦y≦0.08 and 1.1≦y/x≦2.0.
5. The phosphor of claim 1 wherein 1<y/x≦2.
6. The phosphor of claim 1 wherein x=0.04 and 1.5≦y/x≦2.5.
7. The phosphor of claim 1 wherein x=0.05 and 1.4≦y/x≦2.0.
8. The phosphor of claim 1 wherein x=0.06 and 1.2≦y/x≦1.7.
9. The phosphor of claim 1 wherein x=0.07 and 1.1≦y/x≦1.4.
10. A UVC-emitting lamp comprising a discharge vessel containing a source of vacuum ultraviolet radiation and a UVC-emitting phosphor on an interior wall of the discharge vessel, the UVC-emitting phosphor having a composition represented by the formula Sr 1-x Pr x Al 12-y Mg y O 19 wherein 0.01≦x≦0.1, 0.02≦y≦0.15 and y>x.
11. The UVC-emitting lamp of claim 10 wherein the source of vacuum ultraviolet radiation is a xenon excimer discharge.
12. The UVC-emitting lamp of claim 11 wherein the discharge vessel has dielectrically impeded electrodes.
13. The UVC-emitting lamp of claim 10 wherein 1<y/x≦3.
14. The UVC-emitting lamp of claim 10 wherein 0.03≦x≦0.07, 0.06≦y≦0.1 and 1.1≦y/x≦2.7.
15. The UVC-emitting lamp of claim 10 wherein 0.04≦x≦0.07, 0.06≦y≦0.08 and 1.1≦y/x≦2.0.
16. The phosphor of claim 1 wherein the phosphor is formulated with a stoichiometric excess of Sr in an amount of 0.01 moles Sr/mole of phosphor.
17. The UVC-emitting lamp of claim 10 wherein the phosphor is formulated with a stoichiometric excess of Sr in an amount of 0.01 moles Sr/mole of phosphor.
18. A method of making a UVC-emitting phosphor comprising:
(a) forming a mixture of stoichiometric amounts of a source of strontium, a source of aluminum, a source of magnesium and a source of praseodymium according to the formula Sr 1-x Pr x Al 12-y Mg y O 19 wherein 0.01≦x≦0.1, 0.02≦y≦0.15 and y>x; and
(b) firing the mixture in a reducing atmosphere to form the UVC-emitting phosphor.
19. The method of claim 18 wherein the mixture is fired at a temperature between about 1500° C. to about 1600° C.
20. The method of claim 18 wherein the mixture further contains a stoichiometric excess of strontium in an amount of 0.01 moles Sr/mole of phosphor.
21. The method of claim 20 wherein the mixture is fired at a temperature between about 1500° C. to about 1600° C.