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

Abstract

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)³⁺O₈¹³⁻ polyhedra and slightly distorted Nb(Ti)O₆ 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)O₆ 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 ⁵D₀ → ⁷F₂ 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⁺/Dy³⁺. 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.