Emissive compacts and method of making the same
Some phosphor powders can be difficult to form into ceramic compacts because they are difficult to sinter. As described herein, phosphor powders that can degrade under conventional sintering temperatures can be sintered by heating the powder at a lower temperature, such as less than 800° C., while the powder is under greater than atmospheric pressure, such as at least 0.05 GPa. Phosphor ceramic compacts prepared by this method, and light-emitting devices incorporating these phosphor ceramic compacts, are also described.
1. A method of sintering a ceramic, comprising heating a phosphor powder to a temperature less than the degradation temperature of the phosphor powder, wherein the degradation temperature is less than about 800° C., and wherein the heating is done under greater than atmospheric pressure.
2. The method of claim 1 , wherein the phosphor powder is heated at a temperature of about 150° C. to about 750° C.
3. The method of claim 1 , wherein the phosphor powder is heated at a temperature of about 175° C. to about 500° C.
4. The method of claim 1 , wherein the phosphor powder is heated at a pressure of at least 0.05 GPa.
5. The method of claim 4 , wherein the phosphor powder is heated at a pressure of about 0.05 GPa to about 20 GPa.
6. The method of claim 4 , wherein the phosphor powder is heated at a pressure of about 0.5 GPa to about 10 GPa.
7. The method of claim 1 , wherein the phosphor powder has an average particle size of 1 μm to 100 μm.
8. The method of claim 1 , wherein the phosphor powder has an average particle size of about 3 μm to about 75 μm.
9. The method of claim 1 , wherein the phosphor powder comprises a substantially level layer of phosphor particles.
10. The method of claim 1 , wherein the phosphor powder comprises fluoride.
11. The method of claim 10 , wherein the phosphor powder comprises:
(A) A 2 [MF 6 ]:Mn 4+ , wherein A is Li, Na, K, Rb, Cs, NH 4 , or a combination thereof; and wherein M is Ge, Si, Sn, Ti, Zr, or a combination thereof;
(B) E[MF 6 ]:Mn 4+ , wherein E is Mg, Ca, Sr, Ba, Zn, or a combination thereof; and wherein M is Ge, Si, Sn, Ti, Zr, or a combination thereof;
(C) Ba 0.65 Zr 0.35 F 2.70 :Mn 4+ ; or
(D) A 3 [ZrF 7 ]:Mn 4+ , wherein A is Li, Na, K, Rb, Cs, NH 4 , or a combination thereof.
12. The method of claim 1 , wherein the phosphor powder comprises a potassium hexafluorosilicate and a dopant.
13. The method of claim 1 , wherein the phosphor powder comprises a potassium hexafluorotitanate and a dopant.
14. The method of claim 1 , wherein the phosphor powder comprises K 2 TiF 6 :Mn or K 2 SiF 6 :Mn.