PROCESSES FOR PREPARING COLOR STABLE RED-EMITTING PHOSPHORS

摘要

Processes for preparing color stable Mn4+ doped phosphors include contacting a phosphor of formula I with a fluorine-containing oxidizing agent in gaseous form at temperature ≤225°C to form the color stable Mn⁴⁺ doped phosphor Fomula (I)wherein A is independently at each occurrence Li, Na, K, Rb, Cs, or a combination thereof; M is independently at each occurrence 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; and y is 5, 6 or 7. In another aspect, the processes include contacting a phosphor of formula I at an elevated temperature with an oxidizing agent comprising a C₁-C₄ fluorocarbon, to form the color stable Mn⁴⁺ doped phosphor.