UV-emitting phosphor and lamp containing same

• US 7,396,491 B2
• Filed: 04/06/2006
• Issued: 07/08/2008
• Est. Priority Date: 04/06/2006
• Status: Active Grant

• Current Assignee: LEDVANCE LLC (MLS Co. Ltd.)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Synder, Thomas M., Marking, Gregory A.
• Primary Examiner(s): KOSLOW, CAROL M
• Application Number:
  US11/278,823
• Publication Number:
  US 20070235690A1
• Time in Patent Office: 824 Days
• Field of Search: 252/301.4 P, 313/486, 313/643
• US Class Current: 252/301.40P
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 2201/3226 Units using UV-light emitting lasers
• CPC Class Codes: C09K 11/771 with alkaline earth metals
• CPC Class Codes: H01J 61/44 Devices characterised by the luminescent material

Abstract

A UV-emitting phosphor and lamp containing same are described. The phosphor is a praseodymium-activated pyrophosphate-based phosphor which may be represented by the general formula (Ca_2-x,Sr_x)P₂O₇:Pr where 0≦x≦2. The phosphor is excitable by vacuum ultraviolet (VUV) radiation and in particular it may be excited by Xe-excimer discharges and thereby provide a Hg-free UV-emitting lamp. The phosphor exhibits a broad emission in the UVC region in the wavelength range from about 220 nm to about 280 nm with the peak emission occurring in the wavelength range from about 230 nm to about 240 nm. The emission characteristics of the phosphor may be varied depending on the ratio of Sr/Ca.

Claims

1. A UV-emitting phosphor having a composition represented by a formula (Ca_2-x,Sr_x)P₂O₇:

Pr where 0≦

x≦

2.

2. The phosphor of claim 1 wherein the phosphor emits ultraviolet radiation under excitation by vacuum ultraviolet radiation.

3. The phosphor of claim 1 wherein the phosphor emits ultraviolet radiation under excitation by a Xe-excimer discharge.

4. The phosphor of claim 1 wherein the phosphor exhibits a peak emission in a wavelength range from about 230 nm to about 240 nm.

29. The phosphor of claim 1 wherein the phosphor is formulated to have a slight molar excess of pyrophosphate anion relative to the total cation amount.

30. The phosphor of claim 1 wherein the phosphor is formulated to have a ratio of 1.00 moles of pyrophosphate anion to 1.94 moles of cation.

31. The phosphor of claim 1 wherein the phosphor has a mixture of α

- and β

-phases.

5. A UV-emitting phosphor having a composition represented by a formula Ca_(2-w-x-y-z)Sr_xA_yPr_zP₂O₇ where:

A is a 1+ metal cation;

w ranges from 0 to about 0.1;

x ranges from 0 to 2-w-y-z;

y ranges from 0 to about 0.25; and

z ranges from greater than 0 to about 0.12.

6. The phosphor of claim 5 wherein A is Na⁺.

7. The phosphor of claim 5 wherein y ranges from z−

0.01 to z+0.01.

8. The phosphor of claim 5 wherein z ranges from about 0.02 to about 0.08.

9. The phosphor of claim 5 wherein y=z.

10. A UV-emitting phosphor having a composition represented by a formula Ca_(2-w-x-y-z)Sr_xNa_yPr_zP₂O₇ where:

w ranges from 0 to about 0.1;

x ranges from 0 to 2-w-y-z;

y ranges from 0 to about 0.25; and

z ranges from greater than 0 to about 0.12.

11. The phosphor of claim 10 wherein y ranges from z−

0.01 to z+0.01.

12. The phosphor of claim 10 wherein z ranges from about 0.02 to about 0.08.

13. The phosphor of claim 10 wherein y=z.

14. The phosphor of claim 10 wherein w=0.06.

15. The phosphor of claim 14 wherein y=z.

16. A UV-emitting phosphor comprising praseodymium-activated calcium strontium pyrophosphate.

17. A UV-emitting phosphor comprising praseodymium-activated calcium pyrophosphate.

18. The phosphor of claim 17 wherein the phosphor has a composition represented by a formula Ca_(2-w-y-z)A_yPr_zP₂O₇ where:

A is a 1+ metal cation;

w ranges from 0 to about 0.1;

y ranges from 0 to about 0.25; and

z ranges from greater than 0 to about 0.12.

19. The phosphor of claim 18 wherein the phosphor is a β

-phase calcium pyrophosphate and z ranges from about 0.04 to about 0.12.

20. The phosphor of claim 18 wherein the phosphor is an α

-phase calcium pyrophosphate and z ranges from about 0.02 to about 0.08.

21. The phosphor of claim 18 wherein A is Na⁺.

22. A UV-emitting phosphor comprising praseodymium-activated strontium pyrophosphate.

23. The phosphor of claim 22 wherein the phosphor has a composition represented by a formula Sr_(2-w-y-z)A_yPr_zP₂O₇ where:

A is a 1+ metal cation;

w ranges from 0 to about 0.1;

y ranges from 0 to about 0.25; and

z ranges from about 0.03 to about 0.08.

24. The phosphor of claim 22 wherein the phosphor is an α

-phase strontium pyrophosphate.

25. The phosphor of claim 23 wherein y=z.

26. A UV-emitting lamp comprising a discharge vessel containing a source of vacuum ultraviolet radiation and a UV-emitting phosphor on an interior wall of the discharge vessel, the UV-emitting phosphor having a composition represented by a formula (Ca_2-x,Sr_x)P₂O₇:

Pr where 0≦

x≦

2.

27. The UV-emitting lamp of claim 26 wherein the source of vacuum ultraviolet radiation is a xenon excimer discharge.

28. The UV-emitting lamp of claim 27 wherein the discharge vessel has dielectrically impeded electrodes.