Wavelength converting material for a light emitting device
Embodiments of the invention include an infrared-emitting phosphor comprising (La,Gd) 3 Ga 5−x−y Al x SiO 14 :Cr y , where 0≤x≤1 and 0.02≤y≤0.08. In some embodiments, the infrared-emitting phosphor is a calcium gallogermanate material. In some embodiments, the infrared-emitting phosphor is used with a second infrared-emitting phosphor. The second infrared-emitting phosphor is one or more chromium doped garnets of composition Gd 3−x1 Sc 2−x2−y Lu x1+x2 Ga 3 O 12 :Cr y , where 0.02≤x1≤0.25, 0.05≤x2≤0.3 and 0.04≤y≤0.12.
1. A luminescent material, comprising:
a host lattice crystallizing in a trigonal calcium gallogermanate structure type; and
dopants disposed in the host lattice, the dopants comprising:
trivalent chromium; and
tetravalent chromium in a concentration that is less than 1% of a total concentration of all chromium in the luminescent material.
2. The luminescent material of claim 1 , wherein the host lattice comprises a tetravalent cation with an effective atomic radius at least 10% smaller than an effective ionic radius of Cr(IV).
3. The luminescent material of claim 1 , wherein the luminescent material is RE 3 Ga 5−x−y A x SiO 14 :Cr y (RE=La, Nd, Gd, Yb, Tm; A=Al, Sc), where 0≤x≤1 and 0.005≤y≤0.1.
4. The luminescent material of claim 1 , wherein the host lattice is La 3 Ga 5−x SiO 14 .
5. The luminescent material of claim 1 , wherein the luminescent material emits light within a 700-1100 nm range.
6. The luminescent material of claim 1 , wherein the luminescent material is (La,Gd) 3 Ga 5−x−y Al x SiO 14 :Cr y , where 0≤x≤1 and 0.02≤y≤0.08.
7. The luminescent material of claim 6 , wherein the luminescent material is excited by blue or red light.
8. The luminescent material of claim 1 wherein the luminescent material has a full width at half maximum between 1700 cm −1 and 4000 cm −1 .
9. The luminescent material of claim 6 , wherein the band gap of the luminescent material is at least 4.8 eV.
10. The luminescent material of claim 1 wherein the luminescent material is La 2.98 Gd 0.02 Ga 4.76 Al 0.2 SiO 14 :Cr 0.04 .
11. The luminescent material of claim 6 wherein the luminescent material has a full width at half maximum between 1700 cm −1 and 4000 cm −1 .
12. The luminescent material of claim 6 , wherein the luminescent material is La 2.98 Gd 0.02 Ga 4.76 Al 0.2 SiO 14 :Cr 0.04 .
13. A device comprising:
a light source;
the luminescent material of claim 1 ; and
a second luminescent material crystallizing in the cubic garnet structure type.
14. The device of claim 13 wherein the first luminescent material is RE 3 Ga 5−x−y A x SiO 14 :Cr y (RE=La, Nd, Gd, Yb, Tm; A=Al, Sc), where 0≤x≤1 and 0.005≤y≤0.1.
15. The device of claim 13 , wherein the second luminescent material is:
Gd 3−x RE x Sc 2−y−z Ln y Ga 3−w Al w O 12 :Cr z (Ln=Lu, Y, Yb, Tm; RE=La, Nd), where 0≤x≤3; 0≤y≤1.5; 0≤z≤0.3; and 0≤w≤2;
AAEM 1−x F 6 :Cr x (A=Li, Cu; AE=Sr, Ca; M=Al, Ga, Sc) where 0.005≤x≤0.2; or
A 2−x (WO 4 ) 3 :Cr x (A=Al, Ga, Sc, Lu, Yb) where 0.003≤x≤0.5.
16. The device of claim 13 , wherein:
the first luminescent material is (La,Gd) 3 Ga 5−x−y Al x SiO 14 :Cr y , where 0≤x≤1 and 0.02≤y≤0.08; and
the second luminescent material is Gd 3−x1 Sc 2−x2−y Lu x1+x2 Ga 3 O 12 :Cr y , where 0.02≤x1≤0.25, 0.05≤x2≤0.3 and 0.04≤y≤0.12.
17. The device of claim 13 , wherein:
the first luminescent material is La 2.98 Gd 0.02 Ga 4.76 Al 0.2 SiO 14 :Cr 0.04 ; and
the second luminescent material is Gd 2.85 Sc 1.75 Lu 0.3 Ga 3 O 12 :Cr 0.1 .