Narrow band emitting SiAlON phosphor
This specification discloses a method of enhancing the stability and performance of Eu 2+ doped narrow band red emitting phosphors. The resulting phosphor compositions are characterized by crystallizing in ordered structure variants of the UCr 4 C 4 crystal structure type and having a composition of AE 1−x Li 3−2y Al 1+2y−z Si z O 4−4y−z N 4y+z :EU x (AE=Ca, Sr, Ba; 0<x<0.04, 0≤y<1, 0<z<0.05, y+z≤1). It is believed that the formal substitution (Al,O) + by (Si,N) + reduces the concentration of unwanted Eu 3+ and thus enhances properties of the phosphor such as stability and conversion efficiency.
1. A luminescent composition of matter characterized by the formula:
AE 1−x Li 3−2y Al 1+2y−z Si z O 4−4y−z N 4y+z :EU x ;
AE=Ca, Sr, Ba;
0<x<0.04;
0.4<y<0.6;
0<z<0.05; and
a concentration of Si is in a range of a concentration of Eu so that ⅕≤z/x≤4,
the luminescent composition of matter having a tetragonal crystal structure.
2. The luminescent composition of matter of claim 1 , wherein y is equal to or about equal to 0.5.
3. The luminescent composition of matter of claim 1 , crystalized in a UCr 4 C 4 type crystal structure.
4. The luminescent composition of matter of claim 1 , emitting light with an emission peak having a peak wavelength in the range 612 nm to 620 nm and a full width at half maximum ≤55 nm.
5. The luminescent composition of matter of claim 1 , wherein ½≤z/x≤3.
6. The luminescent composition of matter of claim 1 wherein y is equal to or about equal to 0.5, crystalized in a UCr 4 C 4 type crystal structure.
7. The luminescent composition of matter of claim 6 , emitting light with an emission peak having a peak wavelength in the range 612 nm to 620 nm and a full width at half maximum ≤55 nm.
8. A method for making the luminescent composition of matter of claim 1 , comprising
preparing lithium aluminum nitride from lithium nitride and aluminum nitride,
mixing Eu 2 Si 5 N 8 with the lithium aluminum nitride, an oxide, and at least one of a strontium compound, a calcium compound, and a barium compound; and
firing the mixture under nitrogen.
9. A light emitting device comprising:
a semiconductor light emitting device; and
a phosphor composition characterized by the formula
AE 1−x Li 3−2y Al 1+2y−z Si z O 4−4y−z N 4y+z :EU x ;
AE=Ca, Sr, Ba;
0<x<0.04;
0.4<y<0.6;
0<z<0.05; and
a concentration of Si is in a range of a concentration of Eu so that ⅕ ≤z/x≤4;
the phosphor composition having a tetragonal crystal structure and positioned to absorb light emitted by the semiconductor light emitting device and in response emit light of a longer wavelength.
10. The light emitting device of claim 9 , wherein a combined light output from the semiconductor light emitting device and the phosphor composition includes light with an emission peak having a peak wavelength in the range 612 nm to 620 nm and a full width at half maximum ≤55 nm and is perceived as white by a human with normal color vision.
11. The light emitting device of claim 10 , wherein the combined light output from the semiconductor light emitting device and the phosphor composition includes light with an emission peak having a peak wavelength in the range 612 nm to 620 nm and a full width at half maximum ≤55 nm and is characterized by a CRI of 90 or greater.
12. The method of claim 8 , wherein the firing the mixture is performed at 730 C.
13. The method of claim 8 , wherein the oxide compound is aluminum oxide.
14. The method of claim 8 , further comprising mixing lithium fluoride with the Eu 2 Si 5 N 8 , the lithium aluminum nitride, the oxide, and the at least one of a strontium compound, a calcium compound, and a barium compound.
15. The method of claim 8 , further comprising preparing the Eu 2 Si 5 N 8 , preparing the Eu 2 Si 5 N 8 comprising:
mixing europium oxide, silicon nitride and a carbon powder; and
firing the mixture under a gas atmosphere comprising H 2 and N 2 .
16. The method of claim 8 , wherein the at least one of a strontium compound, a calcium compound, and a barium compound is strontium hydride.
17. The method of claim 8 , further comprising mixing one or more of Eu 2 O 3 , EuF 3 , and EuN with the Eu 2 Si 5 N 8 , the lithium aluminum nitride, the oxide, and the at least one of a strontium compound, a calcium compound, and a barium compound.