Blue-green and green phosphors for lighting applications
View Patent ↗Embodiments of the present techniques provide a related family of phosphors that may be used in lighting systems to generate blue or blue-green light. The phosphors include systems having a general formula of: ((Sr 1−z M z ) 1−(x+w) A w Ce x ) 3 (Al 1−y Si y )O 4+y+3(x−w) F 1−y−3(x−w) (I), wherein 0<x≦0.10, 0≦y≦0.5, 0≦z≦0.5, 0≦w≦x, A is Li, Na, K, Rb, or Ag or any combinations thereof, and M is Ca, Ba, Mg, Zn, or Sn or any combinations thereof. Advantageously, phosphors made accordingly to these formulations maintain emission intensity across a wide range of temperatures. The phosphors may be used in lighting systems, such as LEDs and fluorescent tubes, among others, to produce blue and blue/green light. Further, the phosphors may be used in blends with other phosphors, or in combined lighting systems, to produce white light suitable for illumination.
1. A method for producing a phosphor, the method comprising:
providing amounts of oxygen-containing compounds of cerium, silicon, and at least one alkaline-earth metal selected from the group consisting of Sr, Ba, Ca, and combinations thereof;
mixing together the oxygen-containing compounds with a fluoride containing compound to form a mixture; and
then firing the mixture at a temperature between about 900° C. and about 1700° C. under a reducing atmosphere for a sufficient period of time to convert the mixture to a phosphor comprising a general formula of ((Sr 1−z M z ) 1−(x+w) A w Ce x ) 3 (Al 1−y Si y )O 4+y+3(x−w) F 1−y−3(x−w) , wherein 0<x≦0.10, 0<y≦0.5, 0≦z≦0.5, 0swsx, A is Li, Na, K, or any combinations thereof, M is Ca, Ba, or any combinations thereof; and light emitted by the phosphor is blue-green to green in color, having a peak emission wavelength between about 485 nm and about 540 nm, using a 405 nm excitation wavelength.
2. The method according to claim 1 , wherein the oxygen-containing compounds are selected from the group consisting of oxides, hydroxides, carbonates, nitrates, aluminates, silicates, citrates, oxalates, carboxylates, tartarates, stearates, and combinations thereof.
3. A phosphor of formula
((Sr 1−z M z ) 1−(x+w) A w Ce x ) 3 (Al 1−y Si y )O 4+y+3(x−w) F 1−y−3(x−w) ,
wherein
0<x≦0.10;
0<y≦0.5;
0≦z≦0.5;
0swsx;
A is Li, Na, K, or a combination thereof;
M is Ca, Ba, Mg, or a combination thereof; and
light emitted by the phosphor under 405 nm excitation, is blue-green to green in color, having a peak emission wavelength between about 485 nm and about 540 nm, using a 405 nm excitation wavelength.
4. A phosphor according to claim 3 , of formula
((Sr 1−z M z ) 1−x Ce x ) 3 (Al 1−y Si y )O 4+y+3x F 1−y−3x .
5. A phosphor according to claim 3 , wherein M is Ca.
6. A phosphor according to claim 3 , wherein 0<x≦0.015.
7. A phosphor according to claim 4 , wherein M is Ca and 0<x≦0.015.
8. A phosphor according to claim 3 , of formula
(Sr 0.595 Ca 0.4 Ce 0.005 ) 3 (Al 0.6 Si 0.4 )O 4.415 F 0.585 .
9. A phosphor according to claim 3 , of formula
(Sr 0.98 Na 0.01 Ce 0.01 ) 3 (Al 0.9 Si 0.1 )O 4.1 F 0.9 .
10. A phosphor according to claim 3 , of formula
(Sr 0.98 Na 0.01 Ce 0.01 ) 3 (Al 0.8 Si 0.2 )O 4.2 F 0.8 .
11. A phosphor according to claim 3 , of formula
(Sr 0.75 Ca 0.23 Na 0.01 Ce 0.01 ) 3 (Al 0.75 Si 0.25 )O 4.25 F 0.75 .
12. A phosphor according to claim 3 , having a quantum efficiency at about 150° C. that is at least about 80% of the quantum efficiency at a temperature of between about 15° C. and about 25° C.
13. A phosphor according to claim 3 , having a quantum efficiency of at least about 90% of the quantum efficiency of the reference phosphor Sr 4 Al 14 O 25 :Eu 2+ at a temperature of between about 15° C. and about 25° C.
14. A phosphor blend comprising a blue-green to green phosphor having a peak emission wavelength between about 485 nm and about 540 nm, using a 405 nm excitation wavelength, of formula
((Sr 1−z M z ) 1−x+w) A w Ce x ) 3 (Al 1−y Si y )O 4+y+3(x−w) F 1−y−(x−w) ,
wherein
0<x≦0.10;
0<y≦0.5;
0≦z≦0.5;
0swsx;
A is Li, Na, K, or a combination thereof; and
M is Ca, Ba, Mg, or a combination thereof.
15. A phosphor blend according to claim 14 , additionally comprising a complex fluoride doped with Mn 4+ ; (Ba,Sr,Ca) 5 (PO 4 ) 3 (Cl,F,OH):Eu 2+ ; Ca 2 Si 5 N 8 :Ce 3+ ,Eu 2+ ; (Lu,Ca,U,Mg,Y) 1.5 Al 3 Si 9 N 16 :Eu 2+ ,Ce 3+ ; (Ba,Sr,Ca) 2 Si 1−a O 4−2a :Eu 2+ or a combination thereof.
16. A phosphor blend according to claim 14 , wherein the blue-green to green phosphor is of formula
((Sr 1−z M z ) 1−x Ce x ) 3 (Al 1−y Si y )O 4+y+3x F 1−y−3x .
17. A phosphor blend according to claim 14 , wherein M is Ca.
18. A phosphor blend according to claim 14 , wherein 0<x≦0.015.
19. A phosphor blend according to claim 14 , wherein M is Ca and 0<x≦0.015.
20. A phosphor blend according to claim 14 , wherein the blue-green to green phosphor is of formula (Sr 0.595 Ca 0.4 Ce 0.005 ) 3 (Al 0.6 Si 0.4 )O 4.415 F 0.585 .
21. A lighting apparatus comprising:
a light source configured to emit radiation with a peak intensity at a wavelength between about 250 nm and about 550 nm; and
a phosphor composition comprising a blue-green to green phosphor having a peak emission wavelength between about 485 nm and about 540 nm, using a 405 nm excitation wavelength, configured to be radiationally coupled to the light source, of formula
((Sr 1−z M z ) 1−(x+w) A w Ce x ) 3 (Al 1−y Si y )O 4+y+3(x−w) F 1−y−3(x−w) ,
wherein
0<x≦0.10;
0<y≦0.5;
0≦z≦0.5;
0swsx;
A is Li, Na, K, or a combination thereof; and
M is Ca, Ba, Mg, or a combination thereof.
22. A lighting apparatus according to claim 21 , wherein the blue-green to green phosphor is of formula
((Sr 1−z M z ) 1−x Ce x ) 3 (Al 1−y Si y )O 4+y+3x F 1−y−3x .
23. A lighting apparatus according to claim 21 , wherein M is Ca.
24. A lighting apparatus according to claim 21 , wherein 0<x≦0.015.
25. A lighting apparatus according to claim 21 , wherein M is Ca and 0<x≦0.015.
26. A lighting apparatus according to claim 21 , wherein the blue-green to green phosphor is of formula (Sr 0.595 Ca 0.4 Ce 0.005 ) 3 (Al 0.6 Si 0.4 )O 4.415 F 0.585 .