A blue-emitting phosphor is optimized by controlling mole fractions typically of Mg and Si in Sr3-eMgbSi2cO8d:Eue or by further including an optimal amount of at least one additional component such as Ba or Ca. The resulting phosphor exhibits a higher brightness and a higher color purity upon excitation by ultraviolet light emitted as a result of discharge of xenon gas. The optimized phosphor is incorporated into light emitting devices such as lamps and PDPs, and further into display devices.