Tb2(WO4)3:Eu3+ 형광체의 분광학 특성 및 전하 전달 전이 연구

Abstract

The Tb2(WO4)3:Eu3+ phosphors were synthesized by conventional solid state reaction. The structural characteristics of Tb2(WO4)3:Eu3+ were analyzed by using X-ray diffraction from which the single phases of Tb2(WO4)3:Eu3+ lattices are confirmed. The emission and excitation spectra of Tb2(WO4)3:Eu3+ (0.001 - 30 mol%) were obtained under the UV excitation. The excitation spectra of the Tb2(WO4)3:Eu3+ phosphors exhibit absorption band in the wavelength region 250~310 nm due to the O2- – Eu3+ charge transfer transition and spectral lines due to the 4f – 4f transitions of Eu3+ and Tb3+ in the wavelength region 310~470 nm. The strongest excitation line corresponding to the Eu3+ 7F0 → 5L6 transition is observed at 396 nm. The emission lines at 489, 545, 589 nm are attributed to the Tb3+ 5D3, 5D4 → 7FJ transitions, while the lines at 594, 617, 656, 704 nm are due to the Eu3+ 5D0 → 7FJ transitions. No difference in spectral features in the excitation and emission spectra of Eu3+ and Tb3+ is observed for different Eu3+ concentration from 1 to 30 mol%. However, The luminescence intensities of Eu3+ are significantly different from Tb3+ as a function of Eu3+ concentration in Tb2(WO4)3:Eu3+. The emission intensity of Eu3+ increases with increasing Eu3+ concentration up to 30 mol%. However, the rate of increase is not linear with Eu contents for which the quenching by energy diffusion at high Eu concentration is responsible. The intensity of Tb3+ excitation lines of the Eu3+ 615 nm emission increases with increasing Eu concentration up to 1 mol% because of efficient energy transfer from Tb3+ to Eu3+. Over 1 mol% of Eu3+ concentration the excitation and emission intensities are rather reduced. This is attributable for the smaller absorption cross section at higher Eu3+ concentration (lower Tb3+ concentration).