After 10s irradiation, a luminescence from Eu2+ phosphor powder samples was detected which arose from the photo-stimulation of longer wavelengths than F absorption bands. This luminescence was attributed to surface states or intrinsic defects. It was found that the luminescence which arose from photo-stimulation into F bands could be reduced via electron migration from F centers into surface states or intrinsic defects. The use of surface passivation could decrease the numbers of these defects.

W.Chen, M.Su, J.Song, J.Lin: Journal of Applied Physics, 1996, 80[9], 5309-11