The synthesis and luminescent properties of Dy/Re (Re = Tb or Eu) co-doped Gd2(WO4)3 phosphor with tunable color via energy transfer

The new systems of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 ( x  = 0–0.1) and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 ( y  = 0–0.2) phosphors have been successfully obtained using the hydrothermal method at 900 °C in this work. The crystal structure, morphology, PL/PLE spectra, fluorescence and decay analysis have been studied in detail via the combined techniques of XRD , FE-SEM, PLE/PL spectra and decay kinetic. The phase-pure of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 with good dispersions have been formed at the lower sintering temperature of 900 °C. Under 273 nm and 270 nm excitation (the 6 P 7/2 → 8 S 7/2 transitions of Gd 3+ ), the Gd 2 (WO 4 ) 3 :Dy 3+ /Tb 3+ and Gd 2 (WO 4 ) 3 :Dy 3+ /Eu 3+ phosphors exhibit both Dy 3+ (yellow, at 574 nm) and Tb 3+ (green, at 547 nm) as well as Dy 3+ (yellow, at 574 nm) and Eu 3+ (red, at 616 nm) emissions, respectively. The presences of WO 4 2- , Gd 3+ and Dy 3+ excitation bands on the PLE spectra by monitoring the Tb 3+ and Eu 3+ emissions directly provide an evidence of energy transfer of WO 4 2- →Tb 3+ , Gd 3+ →Tb 3+ and Dy 3+ →Tb 3+ , as well as WO 4 2- →Eu 3+ , Gd 3+ →Eu 3+ and Dy 3+ →Eu 3+ , respectively. The quenching concentrations of both two systems are determined to be 7 at% ( x  = 0.07 for Tb 3+ ) and 10 at% ( y  = 0.10 for Eu 3+ ), and the quenching mechanisms of both two systems are mainly due to the Tb 3+ -Tb 3+ and Eu 3+ -Eu 3+ energy transfers, respectively. The color-tunable emission can be achieved though adjusting the relative content ratios of Dy 3+ /Tb 3+ or Dy 3+ /Eu 3+ , which has been verified by the CIE chromaticity coordinates analysis. The energy transfer efficiencies of Dy 3+ →Tb 3+ and Dy 3+ →Eu 3+ have been calculated, and the energy transfer mechanisms have been analyzed in detail. The (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 phosphors with color-tunable emission may have a potential application for w-LEDs.