희토류 이온이 첨가된 LiGd9(SiO4)6O2 형광체의 형광특성 및 에너지 전달

Abstract

Luminescence Properties and Energy Transfer in LiGd9(SiO4)6O2 phosphors doped with rare-earth ions

Seongjin Jin

Department of Physics, The Graduate School, Pukyong National University

Abstract

Rare-earth (Eu, Tb, Ce) doped LiGd9(SiO4)6O2 phosphors were synthesized by solid-state reaction method and their luminescence properties are investigated by optical and laser-excitation spectroscopy. The structural characteristic was investigated by X-ray powder diffraction analysis. The single phases of the LiGd9(SiO4)6O2 phosphors were confirmed. The emission and excitation spectra of the rare-earth ions doped LiGd9(SiO4)6O2 phosphors were obtained under the UV excitation. The difference in excitation and emission spectra in LiGd9(SiO4)6O2:Eu3+ phosphors are discussed in relation with energy transfer from Gd3+ to Eu3 + ions. In the excitation spectra of LiGd9(SiO4)6O2:Eu3+ phosphors, the lines emission are observed at 255, 276 and 314 nm due to the 8S7/2 → 6DJ, 8S7/2 → 6IJ and 8S7/2 → 6PJ transitions. The emission line at 314 nm due to the Gd3+ 6PJ → 8S7/2 transition decreases with increasing Eu3+-concentration in LiGd9(SiO4)6O2 indicating the energy transfer occurs from Gd3+ to Eu3+ ions. The difference in excitation and emission spectra in LiGd9(SiO4)6O2:Tb3+ phosphors are discussed in relation with energy transfer from Gd3+ to Tb3+ ions and cross relaxation between Tb3+ ions. The changes in relative emission intensity between the 5D3 → 7FJ transition and the 5D4 → 7FJ transition are ascribed to the cross relaxation between Tb3+ ions, especially at high Tb3+-concentration in LiGd9(SiO4)6O2. The emission spectra of LiGd9(SiO4)6O2:Ce3+ show the bands at 410 nm corresponding to the 2F5/2 and 2F7/2 states of Ce3+. The red shift of Ce3+-emission is found as the Ce3+-concentration increases, which could be explained by the change in crystal-field symmetry and strength with increasing Ce3+-concentration. It is confirmed that the energy transfer between Gd3+ and Ce3+ , Tb3+ ions occurs from the excitation and emission spectra in Ce3+ and Tb3+ co-doped LiGd9(SiO4)6O2 phosphors. The emission intensity of Ce3+ decreases at high Tb3+ concentration. The changes in relative emission intensity are ascribed to the energy transfer from Ce3+ to Tb3+ ions and cross relaxation between Tb3+ ions.