A process for preparing color stable Mn+4 doped phosphors includes providing a
phosphor of formula I;Ax[MFy]:Mn+4 Iand contacting the
phosphor in particulate form with a saturated solution of a composition of formula II in aqueous
hydrofluoric acid;Ax[MFy]; IIwhereinA is Li, Na, K, Rb, Cs, NR4 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;R is H, lower
alkyl, or a combination thereof;x is the absolute value of the charge of the [MFy]
ion; andy is 5, 6 or 7.In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof.A lighting apparatus capable of emitting
white light includes a
semiconductor light source; and a
phosphor composition radiationally coupled to the
light source, and which includes a color stable Mn+4 doped phosphor.