Influence of co-doping different rare earth ions on CaGa2S4: Eu2+, RE3+(RE=Ln) phosphors

Photoluminescent phosphors CaGa2S4: Eu2+, RE3+ (RE3+ including all rare earth ions except for Sc3+, Pm3+, Eu3+ and Lu3+) were prepared by sintering at high temperature in a reductive atmosphere, and their luminescent properties were studied intensively. The influences of co-doping rare earth ions on their luminescent properties were also investigated. No remarkable differences were found from excitation spectra of co-doped phosphors CaGa2S4: Eu2+, RE3+ in contrast with that of phosphor CaGa2S4: Eu2+, but there were a few differences in emission spectra of Ce3+, Pr3+ or Ho3+ co-doped phosphors. Phosphors CaGa2S4: Eu2+, RE3+ (RE=Ce, Pr, Gd, Tb, Ho and Y) had persistent afterglow, and very short afterglow was shown for Nd3+ or Er3+ co-doped phosphors, but no long afterglow appeared when auxiliary activator was La3+, Sm3+, Dy3+, Tm3+ or Yb3+. Among the phosphors with long-lasting phosphorescence, in our experiments, CaGa2S4: Eu2+, Ho3+ had the longest and the highest brightness long yellow afterglow. Thermo-luminescence of all co-doped phosphors was measured to find the answer of different influences from different rare earth auxiliary activators.