Eu³⁺ -Activated Gd₈ V₂ O₁₇ : Energy Transfer, Luminescence, and Temperature-Dependence Characteristics

A new phosphor of the type Gd_8(1-x) Eu_8 x V₂ O₁₇ (x=0-1.0) was synthesized through the solid-state reaction ceramics method. A pure phase formation was verified by using X-ray powder diffraction measurements. The luminescence of Gd₈ V₂ O₁₇ :Eu³⁺ was investigated through optical and laser excitation spectroscopy. The luminescence curves were investigated in the temperature region 10 to 300 K. Gd₈ V₂ O₁₇ shows a self-activated luminescence under excitation with UV- and near-UV light. The spectra, the decay lifetimes, and the thermal stability of Gd_8(1-x) Eu_8 x V₂ O₁₇ (x=0.005-1.0) strongly depend on both the Eu³⁺ concentration and the temperature. The tunable luminescence is realized by controlling the Eu³⁺ -doping level to adjust the host energy-transfer efficiency from the VO₄^3- groups to the Eu³⁺ activators. At low Eu³⁺ concentrations (<30 mol %), the intensity and lifetime show an unusual change with an increase of the temperature from 10-300 K, that is, the luminescence experiences a straightforward enhancement. The energy transfer from the VO₄^3- group to the Eu³⁺ ions could be accelerated with an increase of the temperature resulting in an unusual enhancement of the Eu³⁺ luminescence and lifetime. However, the emission of the Eu³⁺ ions decreased for highly Eu-doped samples (>30 mol %) with an increase of the temperature. The luminescence mechanism was discussed on the basis of the charge-transfer band of the Eu³⁺ ions, the doping concentration, and the proposed microstructures in the lattices.