Phosphor for light sources and associated light source
View Patent ↗A phosphor for light sources, the emission from which lies in the short-wave optical spectral region, as a garnet structure A 3 B 5 O 12 . It is activated with Ce, the second component B representing at least one of the elements Al and Ga, and the first component A is terbium or terbium together with at least one of the elements Y, Gd, La and/or Lu. In a preferred embodiment, a phosphor having a garnet of structure (Tb 1−x−y RE x CE y ) 3 (Al,Ga) 5 O 12 , where RE=Y, Gd, La and/or Lu; 0≦x≦0.5−y; 0<y<0.1 is used.
1. A method of making a white light source, comprising: encapsulating a light-emitting diode in an epoxy resin having a phosphor dispersed therein, the light emitting diode having an emission from 420 to 490 nm, and the phosphor having a garnet structure as represented by A 3 B 5 O 12 :Ce wherein A is terbium or terbium together with at least one of the elements Y, Gd, La, and/or Lu and B is at least one of the elements Al and Ga, the phosphor converting at least a part of the emission from the light-emitting diode into a longer-wave radiation.
2. The method of claim 1 wherein A is solely or predominately terbium.
3. The method of claim 1 wherein the light-emitting diode has an emission from 430 to 470 nm.
4. The method of claim 2 wherein the light-emitting diode has an emission from 430 to 470 nm.
5. The method of claim 1 wherein B additionally contains In.
6. The method of claim 1 wherein the light-emitting diode is based on Ga(In)N.
7. A method of making a white light source, comprising: encapsulating a light-emitting diode in an epoxy resin having a phosphor dispersed therein, the light emitting diode having an emission from 420 to 490 nm, the phosphor converting at least a portion of the emission from the light-emitting diode into a longer-wave radiation and having a garnet structure represented by
(Tb 1−x−y RE x Ce y ) 3 (Al,Ga) 5 O 12 , where
RE is Y, Gd, La and/or Lu;
0≦x≦0.5−y; and
0<y<0.1.
8. The method of claim 7 wherein x is in the range 0.25≦x≦0.5−y.
9. The method of claim 7 wherein y is in the range 0.02<y<0.06.
10. The method of claim 7 wherein x is in the range 0.25≦x<0.5−y and y is in the range 0.02<y<0.06.
11. The method of claim 7 wherein the light source has a color temperature of below 5000 K.
12. The method of claim 7 wherein the light source has a color temperature of 4500 K.
13. The method of claim 1 wherein the phosphor contains from 0.03 to less than 3 moles of terbium per mole of phosphor.
14. The method of claim 7 wherein the light-emitting diode is based on Ga(In)N.
15. A method of making a white light source, comprising: encapsulating a light-emitting diode in an epoxy resin having a phosphor dispersed therein, the light emitting diode having an emission from 420 to 490 nm, the phosphor converting at least a portion of the emission from the light-emitting diode into a longer-wave radiation, the phosphor having a garnet structure represented by
(Tb x RE 1−x−y Ce y ) 3 (Al,Ga) 5 O 12 , where
RE is Y, Gd, La and/or Lu;
0.01≦x≦0.02; and
0<y<0.1.
16. The method of claim 15 wherein x is 0.01.
17. The method of claim 15 wherein y is in the range 0.01≦y≦0.05.
18. The method of claim 16 wherein y is in the range 0.01≦y≦0.05.
19. The method of claim 16 wherein the phosphor has a garnet structure represented by (Y 0.50 Gd 0.45 Tb 0.01 Ce 0.04 ) 3 Al 5 O 12 .
20. The method of claim 15 wherein the light-emitting diode is based on Ga(In)N.
21. A process for producing a phosphor having a garnet structure as represented by A 3 B 5 O 12 :Ce, wherein A is terbium or terbium together with at least one of the elements Y, Gd, La, and/or Lu and B is at least one of the elements Al and Ga, the process comprising:
(a) intimately mixing cerium oxide, oxides of A and B, and at least one flux to form a mixture; and
(b) firing the mixture in forming gas to form the phosphor.
22. The process of claim 21 wherein the flux is BaF 2 , HBO 3 , or both.
23. The process of claim 21 wherein the forming gas is a mixture of nitrogen and hydrogen gases wherein the hydrogen is 2.3% by volume.
24. The process of claim 21 wherein a stoichiometric excess of an oxide of B is used to form the mixture.
25. The process of claim 21 wherein a stoichiometric excess of aluminum oxide is used to form the mixture.
26. The process of claim 21 wherein A is predominantly or solely terbium.
27. The process of claim 21 wherein the phosphor has a garnet structure represented by
(Tb 1−x−y RE x Ce y ) 3 (Al,Ga) 5 O 12 , where
RE is Y, Gd, La and/or Lu
0≦x≦0.5−y; and
0<y<0.1.
28. The process of claim 21 wherein the mixture is fired at a temperature from 1450° C. to 1550° C.
29. The process of claim 28 wherein the mixture is fired for 3 hours to 6 hours.
30. A process for producing a phosphor having a garnet structure as represented by A 3 B 5 O 12 :Ce, wherein A is terbium or terbium together with at least one of the elements Y, Gd, La, and/or Lu and B is at least one of the elements Al and Ga, the process comprising:
(a) intimately mixing cerium oxide, oxides of A and B, and at least one flux to form a mixture;
(b) firing the mixture in forming gas;
(c) milling the fired mixture; and
(d) firing the mixture in forming gas for a second time to form the phosphor.
31. The process of claim 30 wherein the firings are performed at a temperature from 1450° C. to 1550° C.
32. The process of claim 31 wherein the firings are each for three hours.
33. The process of claim 30 wherein a stoichiometric excess of an oxide of B is used.
34. The process of claim 30 wherein a stoichometric excess of aluminum oxide is used.
35. The process of claim 30 wherein A is predominantly or solely terbium.
36. The process of claim 30 wherein the flux is BaF 2 , HBO 3 , or both.
37. A process for producing a phosphor having a garnet structure as represented by
(Tb 1−x−y RE x Ce y ) 3 (Al,Ga) 5 O 12 , where
RE is Y, Gd, La and/or Lu
0≦x≦0.5−y; and
0<y<0.1;
the process comprising:
(a) intimately mixing cerium oxide and terbium oxide with at least one flux and at least one oxide of RE, Al, and/or Ga, to form a mixture;
(b) firing the mixture in forming gas;
(c) milling the fired mixture; and
(d) firing the mixture in forming gas for a second time to form the phosphor.
38. The process of claim 37 wherein a stoichiometric excess of aluminum oxide is used.
39. The process of claim 37 wherein the firings are performed at a temperature from 1450° C. to 1550° C.
40. The process of claim 39 wherein a stoichiometric excess of aluminum oxide is used.
41. The process of claim 40 wherein the firings are each for three hours.