Color stable red-emitting phosphors

Abstract

A lighting apparatus includes a semiconductor light source in direct contact with a polymer composite comprising a color stable Mn 4+ doped phosphor, wherein the lighting apparatus has a color shift of 1.5 MacAdam ellipses after operating for at least 2,000 hour at a LED current density greater than 2 A/cm 2 , a LED wall-plug efficiency greater than 40%, and a board temperature greater than 25° C.

1 . A lighting apparatus comprising a semiconductor light source in direct contact with a polymer composite comprising a color stable Mn 4+  doped phosphor, wherein the lighting apparatus has a color shift of ≦2 MacAdam ellipses after operating for 30 minutes at a LED current density greater than 70 A/cm 2 , a LED wall-plug efficiency greater than 18%, and a board temperature greater than 25° C. 
     
     
         2 . A lighting apparatus according to  claim 1 , wherein the color stable Mn 4+  doped phosphor is of formula 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. 
       
     
     
         3 . A lighting apparatus according to  claim 1 , wherein M is Si, Ge, Sn, Ti, Zr, or a combination thereof. 
     
     
         4 . A lighting apparatus according to  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.   
     
     
         5 . A lighting apparatus according to  claim 1 , wherein the color stable Mn 4+  doped phosphor is K 2 SiF 6 :Mn 4+ . 
     
     
         6 . A color stable Mn 4+  doped phosphor of formula I, 
       
         
           
           
               
               
           
         
         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 the absolute value of the charge of the [MF y ] ion; 
 y is 5, 6 or 7; and 
 
         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%. 
       
     
     
         7 . A color stable Mn 4+  doped phosphor according to  claim 6 , wherein the % intensity loss of the phosphor is ≦3%. 
     
     
         8 . A color stable Mn 4+  doped phosphor according to  claim 6 , wherein the % intensity loss of the phosphor is ≦1.5%. 
     
     
         9 . A color stable Mn 4+  doped phosphor according to  claim 6 , of formula K 2 SiF 6 :Mn 4+ .