Coated manganese doped phosphors
A process for preparing a population of coated phosphor particles is presented. The process includes combining particles of a phosphor of formula I: A x [MF y ]:Mn 4+ with a first solution including a compound of formula II: A x [MF y ] to form a suspension, where 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 an absolute value of a charge of the [MF y ] ion; and y is 5, 6 or 7. The process further includes combining a second solution including a source A + ions with the suspension.
1. A process for preparing a population of coated phosphor particles comprising:
combining particles of a phosphor of formula I with a first solution comprising a compound of formula II to form a suspension; and
combining a second solution comprising a source of A + ions with the suspension,
A x [MF y ]:Mn 4+ (I)
A x [MF y ] (II)
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 an absolute value of a charge of an [MF y ] ion; and
y is 5, 6, or 7.
2. The process according to claim 1 , wherein
A is Na, K, or a combination thereof; and
M is Si, Ge, Ti, Zr, or a combination thereof.
3. The process according to claim 1 , wherein the source of A + ions comprises a compound selected from a halide, sulphate, phosphate, acetate, and combinations thereof.
4. The process according to claim 3 , wherein the source of A + ions comprises KF, KHF 2 , KCl, KBr, KI, K 2 SO 4 , K 3 PO 4 , CH 3 COOK, or a combination thereof.
5. The process according to claim 1 , wherein the first solution, the second solution or both the first solution and the second solution comprises hydrofluoric acid.
6. The process according to claim 1 , wherein the second solution is added to the suspension at a rate less than 100 milliliters/minute.
7. The process according to claim 1 , wherein the second solution is added to the suspension at a rate in a range from about 0.1 millimeter/minute to about 10 milliliters/minute.
8. The process according to claim 1 , wherein a molar ratio of the source of A + ions to the compound of formula II is in a range from about 1:1 to about 1:20.
9. The process according to claim 1 , wherein the phosphor of formula I is K 2 SiF 6 :Mn 4+ .
10. The process according to claim 1 , wherein the compound of formula II is K 2 SiF 6 .
11. A process for preparing a population of coated phosphor particles comprising:
combining particles of K 2 SiF 6 :Mn 4+ with a first solution comprising K 2 SiF 6 to form a suspension; and
combining a second solution comprising KF with the suspension.
12. The process according to claim 1 , wherein each particle in the population of coated phosphor particles includes a core including a phosphor of formula I and a coating including a compound of formula II.