Processes for preparing color stable red-emitting phosphors

Abstract

Processes for preparing color stable red-emitting phosphors include contacting a complex fluoride phosphor of formula I, AxMFy:Mn4+   I with a first fluorine-containing oxidizing agent in gaseous form at a first temperature ranging from about 200° C. to about 700° C., to form a first product phosphor; contacting the first product phosphor in particulate form with a solution of a compound of formula II in aqueous hydrofluoric acid, AxMFy   II to form a treated phosphor; and contacting the treated phosphor with a second fluorine-containing oxidizing agent in gaseous form at a second temperature of less than 225° C.; 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 MFy ion; and y is 5, 6 or 7.

Dependencies are inferred from the claim text.