Tb^(3+)掺杂Y_2O_3纳米晶体中Tb^(3+)离子4f5d跃迁及能量传递的研究

4f5d Transition and Energy Transfer of Tb^(3+) Doped Y_2O_3 Nanocrystalline

采用燃烧法制备了不同Tb3+掺杂浓度和不同粒径的Y2O3:Tb纳米晶体粉末样品,并通过高温退火获得了相应Tb3+掺杂浓度的体材料样品。测量了纳米和体材料样品的发射光谱、激发光谱、X射线衍射谱和荧光衰减曲线,并拍摄了不同粒径样品的透射电子显微镜(TEM)照片。研究纳米Y2O3∶Tb晶体粉末中Tb3+离子的4f5d跃迁发现,由于在近表面的低结晶度环境和颗粒内部的高结晶度环境中Tb3+离子4f5d跃迁对应的激发峰位置不同,不同粒径样品中处于这两种环境的Tb3+离子比例也不同,激发谱的谱线形状存在较大差别,还对Tb3+离子的能量传递进行了研究,发现Y2O3∶Tb晶体粉末中Tb3+的(5D3,7F6)→(5D4,7F0)能量传递类型为受纳米限域效应影响很大的电偶极电偶极相互作用;引起5D4→7F5(543nm)发光浓度猝灭的是不同Tb3+离子5D4能级之间交换相互类型的能量传递,此类型的能量传递受纳米限域效应影响较小。

Nanocrystal powders of Y2O3 ：Tb with different Tb^3＋ doping concentrations and average sizes were prepared by chemical self-combustion, and the bulk samples of corresponding concentrations were also obtained by annealing nano-materials at high temperatures. The emission spectra, excitation spectrum, X-ray diffraction, transmission electron microscopy images and fluorescence decay curves of Y2O3 ： Tb nanomaterials and bulk materials were measured. Then the 4f^8→ 4f^7 5d^1 transition of Tb^3＋ ions in Y2O3 ：Tb nanocrystal powders was studied. Great difference in the excitation spectral line shapes for different sized Y2O3 ： Tb nanocrystal powders was observed. The change of excitation spectral line shapes is because that the Tb^3＋ ions exist in two very different local environments the low crystallization degree of close surface and high crystallization degree inside the particles.The absorption peaks of 4f5d transition are different in these two environments. Also the ^5 D3→^5 D4 and 5 D4 →^5 D4 energy transfer and luminescence concentration quenching caused by energy transfer were investigated. The （^5 D3 , ^7 F6 ） → （^5 D4 , ^7 F0 ） energy transfer is caused by interaction of electric dipoles, which is greatly affected by the quantum confinement effect. The concentration quenching of ^5 D4→^7F5 luminescence is resulted by the energy transfer of exchange interaction among ^5 D4 （Tb） energy levels of different Tb^3＋ ions. The quantum confinement showed little influence on this type of energy transfer.