Color stable red-emitting phosphors
View Patent ↗A process for synthesizing a color stable Mn 4+ doped phosphor includes contacting a precursor of formula I, in gaseous form at an elevated temperature with a fluorine-containing oxidizing agent to form the color stable Mn 4+ doped phosphor A x [MF y ]:Mn 4+ I wherein A is Li, Na, K, Rb, Cs, NR 4 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; R is H, lower alkyl, 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 lighting apparatus comprising a semiconductor light source; and a color stable Mn 4+ doped phosphor of formula K 2 SiF 6 :Mn 4+ , wherein % intensity loss of the phosphor after exposure to light flux of at least 80 w/cm 2 at a temperature of at least 50° C. for at least 21 hours is ≦4%.
2. A lighting apparatus according to claim 1 , wherein % intensity loss of the phosphor is ≦3%.
3. A lighting apparatus according to claim 1 , wherein % intensity loss of the phosphor is ≦1%.
4. A backlight device comprising a semiconductor light source; and a color stable Mn 4+ doped phosphor of formula K 2 SiF 6 :Mn 4+ , wherein % intensity loss of the phosphor after exposure to light flux of at least 80 w/cm 2 at a temperature of at least 50° C. for at least 21 hours is ≦4%.
5. A backlight device according to claim 4 , wherein % intensity loss of the phosphor is ≦3%.
6. A backlight device according to claim 4 , wherein % intensity loss of the phosphor is ≦1%.
7. A color stable Mn 4+ doped phosphor of formula K 2 SiF 6 :Mn 4+ , wherein % intensity loss of the phosphor after exposure to light flux of at least 80 w/cm 2 at a temperature of at least 50° C. for at least 21 hours is ≦4%.
8. A color stable Mn 4+ doped phosphor according to claim 7 , wherein the % intensity loss of the phosphor is ≦3%.
9. A color stable Mn 4+ doped phosphor according to claim 7 , wherein the % intensity loss of the phosphor is ≦1.5%.