US Patent 9512356 Process for preparing red-emitting phosphors

A process for preparing a Mn4+ doped phosphor of formula IAx[MFy]:Mn+4   Iincludes combining in an acidic solution, an A+ cation, an anion of formula MFy, and a Mnn+ source comprising a fluoromanganese compound, precipitating a Mnn+ containing phosphor precursor from the acidic solution, and contacting the Mnn+ containing phosphor precursor with a fluorine-containing oxidizing agent in gaseous form, at an elevated temperature, to form the Mn4+ doped phosphor;whereinA 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 [MFy] ion;y is 5, 6 or 7; andn is 2 or 3.