Eu3+ 이온이 첨가된 YGd (WO4)3 형광체의 합성과 형광 특성

Abstract

The red-emitting phosphors of Eu3+-doped YGd(WO4)3 were prepared by solid state reaction method. The excitation and emission spectra and decay curves of YGd(WO4)3:Eu3+ (0.01 - 50 mol %) are investigated by the optical and laser excitation spectroscopy at room temperature. The structural characteristics were analyzed by using X-ray diffraction (XRD). No obvious impurity phase was detected. Strong excitation bands due to the ligand to metal ion charge transfer (CT) transition of Eu3+ - O2- are observed in the UV region. The excitation into the CT state causes the strong red emission at 617 nm due to the 5D0 → 7F2 transition. The strongest excitation line at 396 nm is due to the Eu3+ 7F0 → 5L6 transition. The excitation spectra exhibit the weak Gd3+ line at 314 nm corresponding to the 8S7/2 → 6P7/2 transition. Emission spectra under excitation at 285 nm (Eu3+- O2- CT band) and 396 nm (7F0 → 5L6) are almost the same in the spectral features. The emission at 593 nm originates from the 5D0 → 7F1 transition and 617 nm from the 5D0 → 7F2 transition. The strongest emission line at 617 nm is attributed to the induced electric dipole 5D0 → 7F2 transition. Weak emission lines are appeared at 656 nm for the 5D0 → 7F3 transition, 703 nm for the 5D0 → 7F4 transition. The emission intensity increases with increasing Eu3+-concentration up to 30 mol% and then luminescence quenching occurs over 50 mol% of Eu3+-concentration. The decay curves of the 5D0 emission (617 nm) show single exponential with lifetime of about 0.47 ms in YGd(WO4)3:Eu3+. Near the same lifetimes were detected for different Eu3+ concentration from 1 to 50 mol% indicating that no significant luminescence quenching occurs in the YGd(WO4)3:Eu3+ system at high Eu concentration.