Abstract: A single particle penetration phosphor employs La.sub.2 O.sub.2 S:Tb particles as a core particle having a thin layer of La.sub.2 O.sub.2 SO.sub.4 :Tb formed thereon by oxidation to provide a barrier which must be penetrated by excitation electrons to produce narrow bandwidth green spectral emission from the particle. The thin barrier is in turn coated by a layer of YVO.sub.4 :Eu particles which produce narrow bandwidth red spectral emission upon electron excitation. The barrier layer increases the voltage turn on characteristic of the green carrier host thereby causing the electron irradiated phosphor to radiate in the red spectrum for low voltages and in the green spectrum for higher voltages. Additionally, methods are disclosed for synthesizing the above single particle penetration phosphor.