Multi-color luminescence evolution and efficient energy transfer of scheelite-type LiCaGd(WO4)3:Ln3+ (Ln = Eu, Dy, Tb) phosphors

A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO4)(3) (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (D-5(0)-F-7(2)), Dy3+ (F-4(9/2)-H-6(13/2)) and Tb3+ (D-5(4)-F-7(5)) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent.powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy(3+)concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW:xTb(3+)/0.08Dy(3+) samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW:yEu(3+)/0.08Dy(3+) can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln(3+) (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs.