Charge transfer transition and energy transfer in Eu3+-doped Gd10V2O20

Eu3+-doped Gd10(1-x)Eu10xV2O20 (x = 0 - 1) phosphors were synthesized via the sol-gel process. The formation of a single phase compound was verified through the X-ray diffraction studies. Luminescence properties of Gd10V2O20:Eu3+ are investigated by optical and laser excitation spectroscopy. The emission and excitation spectra, luminescence decays were measured in the temperature region 7-300 K. The strong emission due to the vanadate group of Gd10V2O20:Eu3+ is observed at low temperature. The charge transfer transition of Eu3+ depends strongly on the Eu3+-concentration in Gd10V2O20:Eu3+. The emission intensity as a function of Eu3+ concentration under excitation of charge transfer band is inconsistent with that of the 4f7 states (the 5L6 state) of Eu3+. The energy transfer occurs between two Eu3+ ions at low Eu3+ concentration (< 10 mol%), while energy diffusion dominates at high Eu3+ concentration.