Up/down conversion luminescence and energy transfer of Er3+/Tb3+ activated NaGd(WO4)(2) green emitting phosphors

摘要

A series of double scheelite-type tungstate green phosphors NaGd(WO4)(2):Er3+, Tb3+ were synthesized by a hydrothermal route and subsequent calcination process, and they were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometry (EDS), photoluminescence spectroscopy and fluorescence lifetime measurements. The phosphors take on octahedral microcrystals with a mean side length of similar to 2 mu m. In the single doped phosphors system, the energy transfer processes from WO42- to Er3+ or Tb3+ were discussed. The quenching concentrations of Er3+ and Tb3+ are 0.05 and 0.07, respectively. The critical distances for Er3+ and Tb3+ ions are calculated to be 14.28 angstrom and 12.76 angstrom, respectively. When doping Er3+/Tb3+ is applied in the single compound, the concentration quenching effect of Tb3+ ions occurs via a resonant-type dipole-dipole interaction as well as that of Er3+ ions. Under the excitation with ultraviolet (378 nm) or infrared (980 nm) light, the Er3+/Tb3+ co-doped NaGd(WO4)(2) phosphors emit strong green emission. The obtained samples with bright emission intensity and appropriate decay time are suitable for use as green phosphors in the near ultraviolet LEDs and bioimaging applications. (C) 2018 Elsevier B.V. All rights reserved.