Color-tunable luminescence properties of Sm3+/Dy3+ co-doped NaLa(MoO4)2 phosphors and their energy transfer mechanism

Abstract

The Sm3+, Dy3+ doped and Sm3+/Dy3+ co-doped NaLa(MoO4)2 spherical phosphors were hydrothermally synthesized by the EDTA-2Na mediated method. Under the excitation of 297 nm, the quenching concentration of Sm3+ in NaLa(MoO4)2 host was determined to be 13%, and the concentration quenching mechanism was discussed to be the electric quadrupole–quadrupole interaction. After Sm3+ and Dy3+ ions were co-doped into the NaLa(MoO4)2 host, the energy transfer behaviors resulted from Dy3+ to Sm3+ ions were investigated by the help of the luminescent spectra of the obtained phosphors. By varying co-doping concentrations of Sm3+/Dy3+ ions, the emission color of NaLa(MoO4)2:Sm3+/Dy3+ can be tuned from reddish-orange, pink and white to bluish-green. The CIE chromaticity coordinate, the correlated color temperature and the quantum efficiency of NaLa0.87(MoO4)2:1%Sm3+, 12%Dy3+ were calculated to be (0.356, 0.320), 4353 K and 20%, respectively. Furthermore, in the temperature-dependent analysis, it presented good thermal stability, which can become a promising single-phased white-emitting phosphor for white LEDs devices. Based on these results, the possible energy transfer mechanism between Dy3+ and Sm3+ in NaLa(MoO4)2:Sm3+/Dy3+ was also proposed.