Luminescent materials
Embodiments of the invention are directed to a luminescent ceramic including a first phase and a second phase. The first phase is R 3−x−y−z+w2 A 1.5x+y−w2 M z Si 6−w1−w2 Al w1−w2 N 11−y−w1 O y+w1 . R is selected from the group comprising trivalent La, Gd, Tb, Y, Lu; A is selected from the group comprising bivalent Ca, Mg, Sr, Ba, and Eu; and M is selected from the group comprising trivalent Ce, Pr and Sm. The second phase may be or comprise, for example, RE 3 ASi 5 N 9 O 2 and RESi 3 N 5 , wherein RE is at least one rare-earth element selected from the group consisting of La, Gd, Lu, Y, Ce and Sc and wherein A is at least one metal element selected from the group consisting of Ba, Sr, Ca, Mg, Zn and Eu.
1. A luminescent ceramic comprising:
a first phase comprising RE 3−x−y−z+w2 A 1.5x+y−w2 M z Si 6−w1−w2 Al w1+w2 N 11−y−w1 O y+w1 and a dopant, wherein:
0≤x≤2;
0≤y≤3;
0≤z≤3;
0≤w1≤6;
0≤x+y+z−w2≤3;
0≤w1+w2≤6;
0≤w2≤x+y≤3;
R is selected from the group of trivalent La, Gd, Tb, Y, and Lu, and combinations thereof;
A is selected from the group of bivalent Ca, Mg, Sr, Ba, and Eu;
M is selected from the group of trivalent Ce, Pr and Sm; and
a second phase comprising at least one material selected from the group consisting of RE 4−x A x Si 5−w Al w N 10−x−w O 1+x+w , 0≤x≤4, 0≤w≤5, RE 3 A 1−x/2 Si 5−w Al w N 9−x−w O 2+x+w , 0≤x≤2, 0≤w≤5, and RE 1−x A x Si 3−w Al w N 5−x−w O x+w , 0≤x≤1, 0≤w≤3, 0≤x+w≤3, wherein RE is at least one rare-earth element selected from the group consisting of La, Gd, Lu, Y, Ce and Sc and wherein A is at least one metal element selected from the group consisting of Ba, Sr, Ca, Mg, Zn and Eu.
2. The luminescent ceramic of claim 1 wherein the first phase comprises at least 88 wt % of the luminescent ceramic, and the second phase comprises no more than 12 wt % of the luminescent ceramic.
3. The luminescent ceramic of claim 1 wherein the second phase comprises RE 3 ASi 5 N 9 O 2 .
4. The luminescent ceramic of claim 1 wherein the second phase comprises RESi 3 N 5 .
5. The luminescent ceramic of claim 1 wherein the first phase has a different index of refraction from the second phase.
6. The luminescent ceramic of claim 1 further comprising a third phase.
7. The luminescent ceramic of claim 6 wherein the third phase is RE 6+(x/3)−(2y/3)−z A y+z Si 11−u Al u N 20+x−z−u O 1−x+z+u where 0≤x≤3, 0≤y≤3, 0≤u≤3, 0≤z≤4.
8. The luminescent ceramic of claim 1 wherein the luminescent ceramic emits light having a peak wavelength in the range orange-red.
9. The luminescent ceramic of claim 1 wherein the luminescent ceramic emits light having a peak wavelength in the range green-yellow.
10. The luminescent ceramic of claim 1 wherein the second phase is La 3−x Ca 1.5x Si 6 N 11 :Eu 2+ .
11. A light source comprising:
a light emitting diode that emits blue light; and
a wavelength converting structure comprising a luminescent ceramic disposed in a path of the blue light, the luminescent ceramic comprising:
a first phase comprising R 3−x−y−z+w2 A 1.5x+y−w2 M z Si 6−w1−w2 Al w1−w2 N 11−y−w1 O y+w1 and a dopant, wherein:
0≤x≤2;
0≤y≤3;
0≤z≤3;
0≤w1≤6;
0≤x+y+z−w2≤3;
0≤w1+w2≤6;
0≤w2≤x+y≤3;
R is selected from the group of trivalent La, Gd, Tb, Y, and Lu, and combinations thereof;
A is selected from the group of bivalent Ca, Mg, Sr, Ba, and Eu;
M is selected from the group of trivalent Ce, Pr and Sm; and
a second phase comprising at least one material selected from the group consisting of RE 4−x A x Si 5−w Al w N 10−x−w O 1+x+w , 0≤x≤4, 0≤w≤5, RE 3 A 1−x/2 Si 5−w Al w N 9−x−w O 2+x+w , 0≤x≤2, 0≤w≤5, and RE 1−x A x Si 3−w Al w N 5−x−w O x+w , 0≤x≤1, 0≤w≤3, 0≤x+w≤3, wherein RE is at least one rare-earth element selected from the group consisting of La, Gd, Lu, Y, Ce and Sc and wherein A is at least one metal element selected from the group consisting of Ba, Sr, Ca, Mg, Zn and Eu.
12. The light source of claim 11 wherein the luminescent ceramic emits light having a peak wavelength that is yellow or green, the wavelength converting structure further comprising a wavelength converting material that emits light having a peak wavelength that is red.
13. The light source of claim 11 wherein the first phase comprises at least 88 wt % of the luminescent ceramic, and the second phase comprises no more than 12 wt % of the luminescent ceramic.
14. The light source of claim 11 wherein the second phase comprises RE 3 ASi 5 N 9 O 2 .
15. The light source of claim 11 wherein the second phase comprises RESi 3 N 5 .
16. The light source of claim 11 further comprising a third phase.
17. The light source of claim 16 wherein the third phase is RE 6+(x/3)−(2y/3)−z A y+z Si 11−u Al u N 20+x−z−u O 1+x−z−u where 0≤x≤3, 0≤y≤3, 0≤u≤3, 0≤z≤4.
18. The light source of claim 11 wherein the second phase is La 3−x Ca 1.5x Si 6 N 11 :Eu 2+ .
19. The luminescent ceramic of claim 1 , wherein the dopant is selected from one of Ce 2+ , Eu 2+ , or a combination of Ce 2+ and Eu 2+ .
20. The luminescent ceramic of claim 1 , wherein the dopant comprises Eu 2+ , M=0, and A includes at least one of Ca, Mg, Sr, Ba.