Nitride-based, red-emitting phosphors
View Patent ↗Embodiments of the present invention are directed to nitride-based, red-emitting phosphors in red, green, and blue (RGB) lighting systems, which in turn may be used in backlighting displays and warm white-light applications. In particular embodiments, the red-emitting phosphor is based on CaAlSiN 3 type compounds activated with divalent europium. In one embodiment, the nitride-based, red emitting compound contains a solid solution of calcium and strontium compounds (Ca,Sr)AlSiN 3 :Eu 2+ , wherein the impurity oxygen content is less than about 2 percent by weight. In another embodiment, the (Ca,Sr)AlSiN 3 :Eu 2+ compounds further contains a halogen in an amount ranging from about zero to about 2 atomic percent, where the halogen may be fluorine (F), chlorine (Cl), or any combination thereof. In one embodiment at least half of the halogen is distributed on 2-fold coordinated nitrogen (N2) sites relative to 3-fold coordinated nitrogen (N3) sites.
1. A nitride-based, red-emitting phosphor having the formula M a M b M c (N,D) n :E z , where:
Ma is at least one divalent element;
M b is a trivalent element;
M c is a tetravalent element;
N is nitrogen;
E is an activator;
D is a halogen selected from the group consisting of F, Cl, and Br;
wherein the stoichiometric ratios of the constituent elements (a+z):b:c:n are about 1:1:1:3; and
wherein the phosphor contains at least some Br.
2. The nitride-based, red-emitting phosphor of claim 1 , wherein M a is a combination of at least two divalent alkaline earth metals.
3. The nitride-based, red-emitting phosphor of claim 1 , wherein M a is a combination of at least two divalent alkaline earth metals selected from the group consisting of Mg, Ca, Sr, and Ba.
4. The nitride-based, red-emitting phosphor of claim 1 , wherein M a is a combination of Sr and Ca.
5. The nitride-based, red-emitting phosphor of claim 1 , wherein M b is a trivalent metal selected from the group consisting of Al, Ga, Bi, Y, La, and Sm.
6. The nitride-based, red-emitting phosphor of claim 1 , wherein M c is a tetravalent element selected from the group consisting of Si, Ge, P, and B.
7. The nitride-based, red-emitting phosphor of claim 1 , wherein E is at least one or more of the rare earth elements and transition metal elements.
8. The nitride-based, red-emitting phosphor of claim 1 , wherein E is selected from the group consisting of Eu, Ce, Mn, Tb, and Sm.
9. The nitride-based, red-emitting phosphor of claim 1 wherein the phosphor contains less than about 2 percent by weight oxygen.
10. The nitride-based, red-emitting phosphor of claim 1 , wherein the amount of the halogen in the phosphor ranges up to about 0.2 atomic percent.
11. The nitride-based, red-emitting phosphor of claim 1 , wherein the halogen is contained within crystal substitutionally.
12. The nitride-based, red-emitting phosphor of claim 1 , wherein the halogen is contained within the crystal interstitially.
13. The nitride-based, red-emitting phosphor of claim 1 , wherein the halogen is contained within grain boundaries that separate crystalline grains, regions, and/or phases.
14. A nitride-based, red-emitting phosphor having the formula M a M b M c (N,D) n :E z , where:
Ma is at least one divalent element;
M b is a trivalent element;
M c is a tetravalent element;
N is nitrogen;
E is an activator;
D is a halogen selected from the group consisting of F, Cl, and Br;
wherein n ranges from about 2.5 to about 3.5, both endpoints inclusive; and
wherein the phosphor contains at least some Br.
15. A nitride-based, red-emitting phosphor having the formula M m M a M b D 3w N [(2/3)(m+z)+a+(4/3)b-w] Z z , where:
M m is selected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, and Hg, individually or in combinations;
M a is a trivalent metal or semimetal selected from the group consisting of B, Al, Ga, In, Y, Sc, P, As, La, Sm, individually or in combinations;
M b is a tetravalent element selected from the group consisting of C, Si, Ge, Sn, Ni, Hf, Mo, W, Cr, Pb, Ti, and Zr;
D is a halogen selected from the group consisting of F, Cl, and Br;
N is nitrogen; and
Z is an activator selected from the group consisting of Eu, Ce, Mn, Tb, and Sm;
0.01≦m≦1.5;
0.01≦a≦1.5;
0.01≦b≦1.5;
0.0001≦w≦0.6; and
0.0001≦z/(m+z)≦0.5;
wherein the phosphor contains at least some Br.
16. The nitride-based, red-emitting phosphor of claim 15 wherein the phosphor contains less than about 2 percent by weight oxygen.
17. The nitride-based, red-emitting phosphor of claim 15 , wherein the amount of the halogen in the phosphor ranges up to about 0.2 atomic percent.
18. The nitride-based, red-emitting phosphor of claim 15 , wherein the phosphor contains the halogen within the crystal substitutionally.
19. The nitride-based, red-emitting phosphor of claim 15 , wherein the phosphor contains the halogen within the crystal interstitially.
20. The nitride-based, red-emitting phosphor of claim 15 , wherein the halogen is contained within grain boundaries that separate crystalline grains, regions, and/or phases.
21. A nitride-based, red-emitting phosphor having the formula M a M b M c N n :E z D where:
M a is at least one divalent element;
M b is a trivalent element;
M c is a tetravalent element;
N is nitrogen;
E is an activator;
D is a halogen selected from the group consisting of F, Cl, and Br;
wherein the phosphor contains at least some Br;
wherein the stoichiometric ratios of the constituent elements (a+z):b:c:n are about 1:1:1:3; and
wherein the phosphor contains the halogen within the crystal interstitially.
22. A white light illumination system, comprising:
a nitride-based, red-emitting phosphor having the formula M a M b M c (N,D) n :E z , where:
Ma is at least one divalent element;
M b is a trivalent element;
M c is a tetravalent element;
N is nitrogen;
E is an activator;
D is a halogen selected from the group consisting of F, Cl, and Br;
wherein the stoichiometric ratios of the constituent elements (a+z):b:c:n are about 1:1:1:3;
wherein the phosphor contains at least some Br; and
wherein the white light illumination system further contains at least one of a yellow, yellow-green, green, or orange phosphor, individually or in combinations.
23. The white light illumination system of claim 22 , wherein the at least one yellow, yellow-green, green, or orange phosphor is silicate-based or aluminate-based.