A method of making a core-shell phosphor is provided. The method comprises mixing a lanthanum phosphate (LaPO4) core with a shell precursor mixture comprising at least one compound of La, at least one compound of Ce, and at least one compound of Tb to form a core+shell precursor mixture, heating the core+shell precursor mixture to a temperature in a range from about 900° C. to about 1200° C. with an inorganic flux material in presence of a reductant to provide a heated core+shell precursor mixture, cooling the heated core+shell precursor mixture to ambient temperature to provide a product core-shell phosphor dispersed in the inorganic flux material; and separating the product core-shell phosphor from the inorganic flux material.