Core-shell materials with red-emitting phosphors
A coated phosphors that include a shell comprising a first Mn 4+ doped phosphor of formula I A x [MF y ]:Mn 4+ I directly disposed on a core comprising a second phosphor. The second phosphor is a material other than a compound of formula I or formula II A x [MF y ] II wherein A is, independently at each occurrence, Li, Na, K, Rb, Cs, or a combination thereof; M is, independently at each occurrence, 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 for preparing a coated phosphor, the process comprising contacting a suspension of a phosphor material in particulate form in a HF solution, with a source of Mn 4+ , A + , and M, to form a coated phosphor having a shell comprising a first phosphor of formula I,
A x [MF y ]:Mn 4+ I
directly disposed on a core comprising a second phosphor; and
converting the coated phosphor to a color stable coated phosphor by contacting the already formed coated phosphor:
with a fluorine-containing oxidizing agent in gaseous form at an elevated temperature ranging from about 350 degrees Celsius to about 700 degrees Celsius,
and with a compound of formula II, A x [MF y ] in an aqueous hydrofluoric acid, wherein the second phosphor is a material other than a compound of formula I or formula II; and
A x [MF y ] II
wherein:
contact with the compound of formula II in the aqueous hydrofluoric acid is one of: 1, before, or 2, both before and after, the coated phosphor is contacted with the fluorine-containing oxidizing agent in gaseous form at the elevated temperature ranging from about 350 degrees Celsius to about 700 degrees Celsius,
A is, independently at each occurrence, Li, Na, K, Rb, Cs, or a combination thereof;
M is, independently at each occurrence, 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. The process of claim 1 , wherein the second phosphor is a green phosphor.
3. The process of claim 1 , wherein the second phosphor is a Ce 3+ -doped garnet phosphor.
4. The process of claim 1 wherein the second phosphor is (Y,Gd,Tb,La,Sm,Pr,Lu) 3 (Al,Ga) 5-α O 12-3/2α :Ce 3+ (wherein 0≤α≤0.5).
5. The process of claim 1 , wherein the second phosphor is a Eu 2+ -doped β-SiAION phosphor.
6. The process of claim 1 , wherein the second phosphor is CaAISiN 3 : Eu 2+ .
7. The process of claim 1 , wherein the second phosphor is a Eu 2+ -doped nitride phosphor.
8. The process of claim 1 , wherein the second phosphor is (Ba, Sr) 2 Si 5 N 8 :Eu 2+ , (Ca, Sr)AlSiN 3 :Eu 2+ ′ Sr[LiAl 3 N 4 ]:Eu 2+ ′ Sr[Mg 3 SiN 4 ]:Eu 2+ , (Sr, Ca)S:Eu 2+ , or a combination thereof.
9. The process of claim 1 , wherein M is Si, Ge, Sn, Ti, Zr, or a combination thereof.
10. The process of claim 1 , wherein A is Na, K, or a combination thereof.
11. The process of 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.
12. The process of claim 1 , wherein the first phosphor is K 2 SiF 6 :Mn 4+ .