Energy transfer in single phase Eu3+-doped Y2WO6 phosphors

Abstract

Inorganic phosphors based on monoclinic Y₂WO₆ doped with Eu³⁺ ions were prepared via conventional solid-state reactions at high temperature. A total of five samples were obtained with different Eu³⁺ concentrations (0–9%). The purity of the as-prepared phases was checked by powder X-ray diffraction (PXRD). Through the Rietveld refinement, at low concentrations Eu³⁺ ions are found to occupy preferentially the Y2 (2f) sites in the host compound. However, for higher dopant concentrations, the occupancy of the (2e) and (4g) sites becomes relevant. The excitation, emission, and time-resolved emission spectra were examined in detail. Efficient energy transfer from the (WO₆)⁶⁻ groups to the Eu³⁺ activators was observed. The decay curves for the Eu^{3+ 5}D₀ → ⁷F₄ transition show a non-exponential behavior that is enhanced with increasing Eu³⁺ concentration. The experimental decay curves were fitted to the Inokuti–Hirayama model to gain some insight into the mechanism of the interaction between the Eu³⁺ ions in these phosphors.