Near infrared doped phosphors having a zinc, germanium, gallate matrix
Phosphors based on transition metal-activated gallates, particularly Cr 3+ - and Ni 2+ -activated zinc germanium gallates, are disclosed herein. In some embodiments such phosphors can exhibit persistent infrared phosphorescence for as long as 400 hours. Such phosphors can be used, for example, as components of a luminescent paint.
1. A phosphor comprising a material of the formula:
Zn x Ga y Ge z O (x+(3y/2)+2z) :t C, m R
wherein a portion of Ga may optionally be replaced with a Group IIIA metal;
wherein a portion or all of Ge may optionally be replaced with a Group IVA metal; and
wherein C is Cr 3+ , Ni 2+ , or a combination thereof;
R is an ion selected from a group consisting of alkaline earth ions, lanthanide ions, Li + ions, and combinations thereof;
x is 3;
y is 2;
z is 1 to 5;
t is 0.01 to 5 and represents mol % based on the total moles of Ga and any replacements thereof; and
m is 0 to 5 and represents mol % based on the total moles of Ga and any replacements thereof,
wherein the phosphor has at least one emission band in the near infrared.
2. The phosphor of claim 1 wherein t is 0.05 to 2 and represents mol % based on the total moles of Ga and any replacements thereof.
3. The phosphor of claim 1 wherein m is 0 to 2 and represents mol % based on the total moles of Ga and any replacements thereof.
4. The phosphor of claim 1 wherein the alkaline earth ion is selected from the group consisting of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and combinations thereof.
5. The phosphor of claim 1 wherein the lanthanide ion is selected from the group consisting of La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ Yb 3+ , Lu 3+ , and combinations thereof.
6. The phosphor of claim 1 wherein C is Cr 3+ .
7. The phosphor of claim 6 having emission band peaks at 690 to 1100 nm.
8. The phosphor of claim 1 wherein C is Ni 2+ .
9. The phosphor of claim 8 having emission band peaks at 1100 to 1550 nm.
10. The phosphor of claim 1 wherein C is a combination of Cr 3+ and Ni 2+ .
11. The phosphor of claim 10 having emission band peaks at 690 to 1100 nm and 1100 to 1550 nm.
12. The phosphor of claim 1 wherein a portion of Ga is replaced with a Group IIIA metal.
13. The phosphor of claim 12 wherein the Group IIIA metal is Al or In.
14. The phosphor of claim 1 wherein a portion or all of Ge is replaced with a Group IVA metal.
15. The phosphor of claim 14 wherein the Group IVA metal is Si or Sn.
16. The phosphor of claim 1 wherein an emission persists for up to 400 hours after excitation.
17. The phosphor of claim 1 wherein the phosphor is chemically stable in one or more of air, tap water, salt water, seawater, bleach water, and bleach-salt-sodium bicarbonate (NaHCO 3 ) aqueous solution.
18. A luminescent paint comprising a phosphor according to claim 1 .
19. A method of activating a phosphor comprising:
providing a phosphor according to claim 1 ; and
exposing the phosphor to one or more of solar radiation, an ultraviolet lamp, a fluorescent lamp, and a light emitting diode (LED) light.
20. An activated phosphor comprising a phosphor according to claim 1 that has been exposed to one or more of solar radiation, an ultraviolet lamp, a fluorescent lamp, and a light emitting diode (LED) light, and wherein the activated phosphor has an emission that persists for up to 400 hours after excitation.