Hydrothermal synthesis and multicolor luminescence properties of Dy 3+ /Eu 3+ co-doped KLa(MoO 4 ) 2 phosphors

Abstract A series of Dy 3+ /Eu 3+ co-doped KLa(MoO 4 ) 2 phosphors were synthesized by a hydrothermal method. The as-prepared samples were characterized by an X-ray diffraction (XRD), a field emission scanning electron microscope (FE-SEM), a photoluminescence (PL) excitation, emission spectra and decay curves. The samples have a single-phase monoclinic structure of KLa(MoO 4 ) 2 and consist of microspheres with the mean size of 1.5 μm. Upon excitation at 389 nm, KLa(MoO 4 ) 2 :Dy 3+ exhibits characteristic peaks at 485 nm and 576 nm. The optimal doping concentration of Dy 3+ is about 7 mol%. KLa 0.93 −y (MoO 4 ) 2 :0.07Dy 3+ , y Eu 3+ samples show emission peaks of both Dy 3+ and Eu 3+ centered at 485, 576, 595 and 618 nm under 389 nm excitation. It can be found that the integrated emission intensity of Dy 3+ is decreased and the lifetime of Dy 3+ is declined with increasing Eu 3+ concentration, which is due to the energy transfer from Dy 3+ to Eu 3+ . Furthermore, according to Dexter's theory and Reisfeld's approximation, the quadrupole–quadrupole (q–q) interaction is the mechanism for energy transfer between Dy 3+ and Eu 3+ . Moreover, the chromaticity color coordinates of KLa 0.93− y (MoO 4 ) 2 :0.07Dy 3+ , y Eu 3+ samples are tuned from the yellowish-white region to white light and eventually to the reddish-white region with increasing Eu 3+ content. This kind of multicolor tunable phosphors exhibits the great potential applications in the fields of white light diodes, full-color displays and optoelectronic devices.