Crystal structure, luminescence properties and energy transfer of Eu3+/Dy3+ doped GdNbTiO6 broad band excited phosphors

GdNbTiO6 is used as a host material for phosphors for the first time. Lanthanide ion (Eu3+/Dy3+) doped GdNbTiO6 phosphors were prepared by solid-state reaction, and the crystal structure, luminescence properties, and relevant luminescence mechanisms were investigated. The crystal structure of Eu3+/Dy3+ doped GdNbTiO6 was refined from powder XRD data by the Rietveld method, which is made up of irregular (Gd/Eu/Dy)O-3+(8)13- polyhedra and slightly distorted Nb(Ti)O-6 octahedra forming a layered structure. The luminescence properties of the GdNbTiO6:Eu3+/Dy3+ phosphors were studied under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. The GdNbTiO6 host shows a broad emission band about the 400-650 nm region centered at 509 nm owing to the Nb(Ti)O-6 octahedral groups, which has spectral overlap with f-f excitation transitions of Eu3+/Dy3+ in the doped samples. For red phosphor GdNbTiO6:Eu3+, a dominant emission peak at 614 nm was attributed to the D-5(0) -> F-7(2) transition of Eu3+, which confirmed that Eu3+ ions are located at sites without inversion symmetry. The phosphor GdNbTiO6: Dy3+ shows bright yellow-green emission prevailing at 577 nm upon 273 nm excitation. With increasing activator concentration, the emission derived from the characteristic f-f transitions of Eu3+/Dy3+ is enhanced while the host emission is weakened, which is due to the energy transfer from the host to Eu3+/D3+. Considering the facile synthesis and excellent Eu3+/Dy3+ doped luminescence properties of this compound, self-activated GdNbTiO6 may be a good candidate as a host phosphor for use in various optical devices.