LUMINESCENCE, ABSORPTION, AND SITE SYMMETRY OF CE ACTIVATED SRGA2S4 PHOSPHORS

Ce activated SrGa2S4 blue emitting phosphors were examined using elect ron paramagnetic resonance and x-ray diffraction to determine the loca l environment and oxidation state of the Ce ion. Photothermal deflecti on and photoluminescence spectroscopies were applied to determine abso rption and emission characteristics. It is found that the majority of the Ce3+ ions substitute for the eightfold coordinated antiprismatic S r2+ cations in the structure. Our results show that the Ce ions exhibi t C-3h symmetry; this suggests that they are ninefold coordinated. Thi s coordination may arise from a nearby S interstitial, energetically f avorable because of charge compensation. To achieve this symmetry, onl y minor rearrangements of the eight S atoms in the antiprismatic confi guration are required. (C) 1997 American Institute of Physics.