Processes for preparing color stable red-emitting phosphor particles having small particle size
A process for preparing a Mn +4 doped phosphor of formula I A x [MF y ]:Mn +4 I includes combining a first solution comprising a source of A and a second solution comprising H 2 MF 6 in the presence of a source of Mn, to form the Mn +4 doped phosphor; wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is the absolute value of the charge of the [MF y ] ion; y is 5, 6 or 7; and wherein a value of a Hammett acidity function of the first solution is at least −0.9. Particles produced by the process may have a particle size distribution with a D 50 particle size of less than 10 μm.
1. A Mn +4 doped phosphor of formula I comprising a monodisperse population of particles having a particle size distribution comprising a D 50 particle size of less than 1 μm;
A x [MF y ]:Mn +4 I
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, 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;
wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1; and
wherein the phosphor is coated with a manganese-free shell comprising KMgF 3 .
2. A Mn +4 doped phosphor according to claim 1 , wherein the phosphor is OH-free.
3. A Mn +4 doped phosphor according to claim 1 , wherein the phosphor is carbon-free.
4. A Mn +4 doped phosphor according to claim 1 , of formula K 2 SiF 6 :Mn.
5. A lighting apparatus comprising a Mn +4 doped phosphor according to claim 1 .
6. A backlight device comprising a Mn +4 doped phosphor according to claim 1 .
7. A direct emission display device comprising a Mn +4 doped phosphor according to claim 1 .
8. A Mn +4 doped phosphor according to claim 1 , wherein the phosphor has a quantum efficiency exceeding 85% under blue excitation.
9. A Mn +4 doped phosphor according to claim 1 , wherein the phosphor comprises an amount of manganese ranging from about 1.82 wt % to about 5.1 wt % based on total phosphor weight.
10. A Mn +4 doped phosphor according to claim 1 , wherein a span of the particle size distribution is less than 1.1.
11. A Mn +4 doped phosphor according to claim 1 , wherein the composition further comprises one or more materials selected from the group consisting of other phosphors, quantum dot materials and combinations thereof.
12. A Mn +4 doped phosphor of formula I comprising a monodisperse population of particles having a particle size distribution comprising a D 50 particle size of less than 1 μm;
A x [MF y ]:Mn +4 I
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, 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;
wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1,
wherein the phosphor has a quantum efficiency exceeding 85% under blue excitation,
wherein the phosphor comprises an amount of manganese ranging from about 1.82 wt % to about 5.1 wt % based on total phosphor weight, and
wherein the phosphor is coated with a manganese-free shell comprising KMgF 3 .
13. A Mn +4 doped phosphor according to claim 12 , wherein the manganese-free shell is coated with an outer coating layer comprising one or more ligands.
14. A Mn +4 doped phosphor of formula I comprising:
a monodisperse population of particles having a particle size distribution comprising a D 50 particle size of less than 10 μm;
A x [MF y ]:Mn +4 I
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, 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;
wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1; and
wherein the phosphor is coated with a manganese-free shell comprising KMgF 3 .
15. A Mn +4 doped phosphor of formula I comprising:
a monodisperse population of particles having a particle size distribution comprising a D 50 particle size of less than 10 μm;
A x [MF y ]:Mn +4 I
wherein
A is Li, Na, K, Rb, Cs, or a combination thereof;
M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, 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;
wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1,
wherein the phosphor has a quantum efficiency exceeding 85% under blue excitation,
wherein the phosphor comprises an amount of manganese ranging from about 1.82 wt % to about 5.1 wt % based on total phosphor weight; and
wherein the phosphor is coated with a manganese-free shell comprising KMgF 3 .