Thermoluminescent properties of Eu~(2+) and RE~(3+) co-doped phosphors CaGa_2S_4:Eu~(2+) , RE~(3+) (RE = Ln, excluding Pm, Eu and Lu)

摘要

The thermo-luminescence (TL) of rare earth ions RE~(3+) (RE = Ln, excluding Pm, Eu and Lu) co-doped phosphors CaGa_2S_4:Eu~(2+), RE~(3+) was studied between room temperature and 300℃, and 3D thermo-luminescence of the phosphors were measured from room temperature to 400℃. The basic material CaGa_2S_4:Eu~(2+), showed at least two bands in the TL glow curve. Changing the auxiliary activator RE~(3+) (rare earth ion), intensities and the positions of the TL glow curve peaks were affected significantly. For the phosphors with long afterglow, auxiliary activator such as Ce~(3+), Pr~(3+), Gd~(3+), Tb~(3+), Ho~(3+), or Y~(3+) created some new defects in these compounds at lower trap levels and enhanced their TL intensities. The Nd~(3+) or Er~(3+) auxiliary activator only enhanced TL intensities to a low extent, so these two phosphors have short persistent luminescence at room temperature. TL intensities of La~(3+), Sm~(3+) , Tm~(3+) or Yb~(3+) co-doped phosphors were suppressed greatly and no afterglow was shown. The relationship between auxiliary activators and corresponding thermo-luminescence curves of phosphors CaGa_2S_4:Eu~(2+), RE~(3+) are discussed in detail. According to our results, suitable activation energy and enough high corresponding trap density are necessary for the phosphor with long afterglow.