Red-emitting nitride-based calcium-stabilized phosphors
Red-emitting phosphors may comprise a nitride-based composition represented by the chemical formula M a Sr b Si c Al d N e Eu f , wherein: M is at least one of Mg, Ca, Sr, Ba, Y, Li, Na, K and Zn, and 0<a<1.0; 1.5<b<2.5; 4.0≦c≦5.0; 0≦d≦1.0; 7.5<e<8.5; and 0<f<0.1; wherein a+b+f>2+d/v and v is the valence of M. Furthermore, nitride-based red-emitting phosphor compositions may be represented by the chemical formula M x M′ 2 Si 5−y Al y N 8 :A, wherein: M is Mg, Ca, Sr, Ba, Y, Li, Na, K and Zn, and x>0; M′ is at least one of Mg, Ca, Sr, Ba, and Zn; 0≦y≦0.15; and A is at least one of Eu, Ce, Tb, Pr, and Mn; wherein x>y/v and v is the valence of M, and wherein the red-emitting phosphors have the general crystalline structure of M′ 2 Si 5 N 8 :A.
1. A red-emitting phosphor comprising a nitride-based composition represented by the chemical formula M a Sr b Si c Al d N e Eu f , wherein:
M is Ca, and 0.1≦a≦0.4;
1.5<b<2.5;
4.0≦c≦5.0;
0.1≦d≦0.15;
7.5<e<8.5; and
0<f<0.1;
wherein a+b+f>2+d/v and v is the valence of M.
2. The red-emitting phosphor of claim 1 , further comprising at least one of F, Cl, Br and O.
3. The red-emitting phosphor of claim 1 , wherein said red-emitting phosphor is selected from the group consisting of:
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.3 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.4 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.88 Al 0.12 N 8 ; and
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.88 Al 0.12 N 8 .
4. The red-emitting phosphor of claim 1 , wherein said red-emitting phosphor is configured such that under excitation by a blue LED the reduction in photoluminescent intensity after 800 hours of aging at about 85° C. and about 85% humidity is no greater than about 15%.
5. The red-emitting phosphor of claim 1 , wherein said red-emitting phosphor is configured such that the deviation in chromaticity coordinates CIE Δx and CIE Δy after 800 hours of aging at about 85° C. and about 85% relative humidity is less than or equal to about 0.015 for each coordinate.
6. The red-emitting phosphor of claim 5 , wherein the deviation in chromaticity coordinates CIE Δx and CIE Δy is less than or equal to about 0.005 for each coordinate.
7. The red-emitting phosphor of claim 1 , wherein said red-emitting phosphor absorbs radiation at a wavelength ranging from about 200 nm to about 550 nm and emits light with a photoluminescence peak emission wavelength greater than 620.0 nm.
8. The red-emitting phosphor of claim 1 , wherein said red-emitting phosphor consists of Ca, Sr, Si, Al, N, Eu and at least one of F, Cl, Br and O.
9. A red-emitting phosphor comprising a nitride-based composition represented by the chemical formula M a Sr b Si c Al d N e Eu f , wherein:
M is at least one of Mg, Ca, Sr, Ba, Y, Li, Na, K and Zn, and 0<a<1.0;
1.5<b<2.5;
4.0≦c≦5.0;
0<d<1.0;
7.5<e<8.5; and
0<f<0.1;
wherein a+b+f>2+d/v and v is the valence of M, and wherein said red-emitting phosphor has the general crystalline structure of Sr 2 Si 5 N 8 :Eu with M and Al incorporated therein.
10. The red-emitting phosphor of claim 9 , wherein Al substitutes for Si within said general crystalline structure and M is located within said general crystalline structure substantially at interstitial sites.
11. The red-emitting phosphor of claim 9 , further comprising at least one of F, Cl, Br and O.
12. The red-emitting phosphor of claim 9 , wherein M is Ca, 0.1≦d≦0.15 and 0.1≦a≦0.4.
13. The red-emitting phosphor of claim 12 , wherein said red-emitting phosphor is selected from the group consisting of:
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.3 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.4 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.88 Al 0.12 N 8 ; and
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.88 Al 0.12 N 8 .
14. The red-emitting phosphor of claim 12 , wherein said red-emitting phosphor absorbs radiation at a wavelength ranging from about 200 nm to about 550 nm and emits light with a photoluminescence peak emission wavelength greater than 620.0 nm.
15. A red-emitting phosphor comprising a nitride-based composition represented by the chemical formula M x M′ 2 Si 5−y Al y N 8 :A, wherein:
M is at least one of Mg, Ca, Sr, Ba, Y and Li, and 0.1≦x≦0.4;
M′ is at least one of Mg, Ca, Sr, Ba, Y and Li;
0.1≦y≦0.15; and
A is at least one of Eu, Ce, Tb, Pr, Sm and Mn;
wherein x>y/v and v is the valence of M, and wherein said red-emitting phosphor has the general crystalline structure of M′ 2 Si 5 N 8 :A.
16. The red-emitting phosphor of claim 15 , wherein said red-emitting phosphor absorbs radiation at a wavelength ranging from about 200 nm to about 550 nm and emits light with a photoluminescence peak emission wavelength greater than 620.0 nm.
17. The red-emitting phosphor of claim 15 , wherein said red-emitting phosphor is configured such that the deviation in chromaticity coordinates CIE Δx and CIE Δy after 800 hours of aging at about 85° C. and about 85% relative humidity is less than or equal to about 0.015 for each coordinate.
18. The red-emitting phosphor of claim 17 , wherein the deviation in chromaticity coordinates CIE Δx and CIE Δy is less than or equal to about 0.005 for each coordinate.
19. The red-emitting phosphor of claim 15 , further comprising at least one of F, Cl, Br and O.
20. The red-emitting phosphor of claim 15 , wherein said red-emitting phosphor consists of Ca, Sr, Si, Al, N, Eu and at least one of F, Cl, Br and O.
21. The red-emitting phosphor of claim 15 , wherein M′ is Sr.
22. The red-emitting phosphor of claim 21 , wherein M is Ca.
23. The red-emitting phosphor of claim 15 , wherein RE is Eu.
24. A white light emitting device comprising:
a solid state excitation source with emission wavelength within a range from 200 nm to 480 nm;
a red-emitting phosphor comprising a nitride-based composition represented by the chemical formula M a Sr b Si c Al d N e Eu f , wherein:
M is Ca, and 0.1≦a≦0.4;
1.5<b<2.5;
4.0≦c≦5.0;
0.1≦d≦0.15;
7.5<e<8.5; and
0<f<0.1;
wherein a+b+f>2+d/v and v is the valence of M, said red-emitting phosphor being configured to absorb excitation radiation from said excitation source and to emit light having a peak emission wavelength in the range from about 626 nm to about 632.71 nm; and
a yellow/green-emitting phosphor having a peak emission wavelength in the range from about 500 nm to about 580 nm.
25. The white light emitting device of claim 24 , wherein said red-emitting phosphor is configured to absorb excitation radiation from said excitation source and to emit light having a peak emission wavelength in the range from about 626 nm to about 629 nm.
26. The white light emitting device of claim 24 , wherein said red-emitting phosphor has the formula Eu 0.05 Ca 0.1 Sr 1.95 Si 4.88 Al 0.12 N 8 .
27. The white light emitting device of claim 24 , wherein said excitation source has an emission wavelength within a range from 450 nm to 470 nm.
28. The white light emitting device of claim 24 , wherein said red-emitting phosphor further comprises at least one of F, Cl, Br and O.
29. The white light emitting device of claim 24 , wherein said red-emitting phosphor is selected from the group consisting of:
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.3 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.4 Sr 1.95 Si 4.9 Al 0.1 N 8 ;
Eu 0.05 Ca 0.1 Sr 1.95 Si 4.88 Al 0.12 N 8 ; and
Eu 0.05 Ca 0.2 Sr 1.95 Si 4.88 Al 0.12 N 8 .
30. The white light emitting device of claim 24 , wherein said red-emitting phosphor consists of Ca, Sr, Si, Al, N, Eu and at least one of F, Cl, Br and O.