Different luminescent behaviors between photoluminescence and persistent luminescence in Tb3+ doped Li2CaGeO4 phosphors

Different contents of Tb3+ ions doped Li2CaGeO4 phosphors were prepared successfully by the traditional high temperature solid-state reaction method. The influences of Tb3+ ions concentrations on photoluminescence (PL), long persistent luminescence (LPL) and thermoluminescence (TL) properties were studied systematically. The cross-relaxation of Tb3+ in Li2CaGeO4 host was observed in PL when the doping concentration of Tb3+ exceeded 2% but not in LPL. The optimal concentration of Tb3+ for LPL was about 1%. The escaped charge carriers from shallower trap can be re-trapped by deeper traps. A tentative schematic was proposed to illuminate the mechanism of LPL. Besides, the different luminescent behaviors of Tb3+ in Li2CaGeO4 host between PL and LPL were also discussed accordingly.