A method includes obtaining particles of a phosphor precursor of formula Ax[MFy]:Mn4+, reducing sizes of the particles of the phosphor precursor by wet milling the particles and annealing the particles that are wet milled by contacting the particles with a fluorine-containing oxidizing agent. Additionally, a manganese doped complex fluoride phosphor prepared by this method is provided. A lighting apparatus and backlight device that include manganese-doped phosphor prepared by this method also are provided.