The effect of Co-doping by Ca2+, Ta5+, Sn4+, and Ru4+ ions on the X-ray luminescent properties of Gd2O2S:Tb3+ phosphors

Photo-, radio-, thermo-luminescence properties and afterglow decay kinetics are reported for Gd 2 O 2 S:Tb 3+ X-ray phosphor samples co-doped by Ca 2+ , Ta 5+ , Sn 4+ , and Ru 4+ ions. A strong influence of co-doping on the optical properties was found, which can be explained by the influence of the excess or lack of charge in the lattice due to aliovalent ions on the concentration of point defects. Possible microscopic processes are proposed.