Processes for preparing stable red-emitting phosphors
Processes for producing stable Mn 4+ doped phosphors include dispersing a compound of formula I in a solution comprising a compound of formula II to form a dispersion; applying pressure to the dispersion at a temperature less than 200° C. to form a phosphor product; and contacting the phosphor product with a fluorine-containing oxidizing agent in gaseous form at an elevated temperature; wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is the absolute value of the charge of the [MF y ] ion; and y is 5, 6 or 7.
1. A process comprising
dispersing a compound of formula I in a solution comprising a compound of formula II to form a dispersion;
applying pressure to the dispersion at a temperature less than 200° C. to form a phosphor product; and
contacting the phosphor product with a fluorine-containing oxidizing agent in gaseous form at an elevated temperature;
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
x is the absolute value of the charge of the [MF y ] ion; and
y is 5, 6 or 7.
2. A process according to claim 1 , wherein the pressure is less than 100 bar.
3. A process according to claim 1 , wherein the pressure ranges from about 60 bar to about 100 bar.
4. A process according to claim 1 , wherein the pressure is applied for a time less than 4 hours.
5. A process according to claim 1 , wherein the pressure is applied for a time less than 1 hour.
6. A process according to claim 1 , wherein the temperature ranges from about 100° C. to less than 200° C.
7. A process according to claim 1 , wherein the temperature ranges from about 130° C. to 160° C.
8. A process according to claim 1 , additionally comprising exposing the dispersion to microwave radiation while applying pressure.
9. A process according to claim 1 , additionally comprising contacting the color stable Mn4+ doped phosphor in particulate form with a solution of a composition of formula II in aqueous hydrofluoric acid.
10. A process according to claim 1 , wherein the fluorine-containing oxidizing agent is F 2 .
11. A process according to claim 1 , wherein M is Si, Ge, Sn, Ti, Zr, or a combination thereof.
12. A process according to claim 1 , wherein
A is Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Ti, or a combination thereof; and
Y is 6.
13. A process according to claim 1 , wherein the compound of formula I is K 2 SiF 6 :Mn 4+ .
14. A process for synthesizing a color stable Mn 4+ doped phosphor, the process comprising applying pressure to a dispersion at a temperature less than 200° C. to form a first phosphor product, the dispersion comprising a compound of formula I, a compound of formula II and hydrofluoric acid;
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
x is the absolute value of the charge of the [MF y ] ion; and
y is 5, 6 or 7.
15. A process comprising
contacting a compound of formula I with a fluorine-containing oxidizing agent in gaseous form at an elevated temperature to form phosphor product;
A x [MF y ]:Mn 4+ I
dispersing the phosphor product in a solution comprising a compound of formula II and hydrofluoric acid; and
A x [MF y ] II
applying pressure to the dispersion at a temperature less than 200° C.;
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
x is the absolute value of the charge of the [MF y ] ion; and
y is 5, 6 or 7.
16. A process according to claim 15 , wherein the pressure is less than 100 bar.
17. A process according to claim 15 , wherein the pressure ranges from about 60 bar to about 100 bar.
18. A process according to claim 15 , wherein the pressure is applied for a time less than 4 hours.
19. A process according to claim 15 , wherein the pressure is applied for a time less than 1 hour.
20. A process according to claim 15 , wherein the temperature ranges from about 100° C. to less than 200° C.
21. A process according to claim 15 , wherein the temperature ranges from about 130° C. to 160° C.
22. A process according to claim 15 , additionally comprising exposing the dispersion to microwave radiation while applying pressure.
23. A process according to claim 15 , additionally comprising contacting the color stable Mn4+ doped phosphor in particulate form with a solution of a composition of formula II in aqueous hydrofluoric acid.
24. A process according to claim 15 , wherein the fluorine-containing oxidizing agent is F 2 .
25. A process according to claim 15 , wherein M is Si, Ge, Sn, Ti, Zr, or a combination thereof.
26. A process according to claim 15 , wherein
A is Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Ti, or a combination thereof; and
Y is 6.
27. A process according to claim 15 , wherein the compound of formula I is K 2 SiF 6 :Mn 4+ .