Photoluminescence and energy transfer of Tm3+ doped LiIn (WO4)2 blue phosphors

Room temperature steady and time resolved emission spectra of LiIn1-xTmx(WO4)2 (where thulium concentration is 0, 0.5, 1, 5 and 10 at%) blue phosphors, under UV excitation energy have been investigated. The concentration quenching effect on the blue emission, due to the (WO4)-2 groups and 1G4→3H6 emission transition of Tm3+ were studied. Two energy transfer mechanisms are shown. The first takes place between excited (WO4)-2 groups and the 1G4 energy level of Tm3+, and is mainly analyzed by phonon-assisted energy transfer. The second mechanism is due to an energy transfer from the excited Tm3+ ions to the surrounding ground state Tm3+ ions. The non-exponential decay curves of the 1G4 level observed for higher concentrations are analyzed by the Inokuti-Hirayama model. We think that the quenching effect between Tm3+ ions is mainly linked to the dipole-dipole interactions.