980nm激发下Tm^(3＋)诱导的Gd^(3＋)上转换发光性质研究

Study on Ultraviolet Upconversion Emissions of Gd^(3+) Induced by Tm^(3+) under 980 nm Excitation

通过简单温和水热法,制备了系列Tm3+/Yb3+共掺GdF3粉末。用X射线衍射仪和场发射扫描电镜对样品进行了结构和形貌表征。在980 nm半导体连续激光二极管激发下,用荧光光谱仪对氩气保护下退火后的粉末样品进行了上转换发射光谱表征。粉末上转换发光动力学过程是在脉冲(脉宽10 ns,重复频率10 Hz)YAG∶Nd激光器激发光参量振荡器至980 nm激发下研究的,发光信号由单色仪和示波器记录。文章主要讨论了Gd3+的311.6 nm(6P7/2→8S7/2)的发光动力学行为。发光动力学分析结果表明:在980 nm激发下,Gd3+,作为一种基质离子,其发光是由Yb3+作为一级敏化离子通过多步能量传递把能量传递给Tm3+使其布居至3P2能级;然后Tm3+作为二级敏化离子通过能量传递过程3P2→3H6(Tm3+):8S7/2→6IJ(Gd3+)把能量传给Gd3+;进一步,Gd3+与Yb3+或Tm3+之间通过能量传递过程布居至高激发多重态6DJ能级;最后,可观察到Gd3+的激发态6D9/2,6IJ,6P5/2及6P7/2至基态8S7/2的发射。同时,Tm3+在其自身发光过程中也充当激活剂,除了3P2及1I6至3H6的发射外,其他发射不作研究。文章还研究了基质Gd3+依赖于Yb3+浓度、Tm3+浓度、退火温度及激发功率密度的紫外上转换发光性质。

Series of Tm^3＋/Yb^3＋ co-doped GdFa powders were synthesized through an easy and mild hydrothermal method. The phase and purity of powders were characterized by powder X-ray diffraction （XRD） （Rigaku RU-200b）. The morphologies of the samples were characterized by field emission scanning electron microscopy （FE-SEM） （Hitachi S-4800）. The ultraviolet （UV） up-conversion （UC）emission spectra were recorded by a fluorescence spectrophotometer （Hitachi F-4500） with a 980 nm semiconductor continuous wave laser diode as the excitation source. And the luminescent dynamics was measured by excitation with 980 nm using an optical parameter oscillator （OPO） laser pumped by a pulsed Nd ： YAG laser with a pulse duration of 10 ns, repetition frequency of 10 Hz, and the signal was recorded by using a monoehromator and an oscillograph. Under 980 nm excitation, Gd^3＋ , acting as a kind of host ion in the studied system, and its UV UC emissions were observed and studied. The luminescent dynamics of the characteristic emission of Gd^3＋ （311.6 nm, ^6p7/2→^8S7/2） was explored and studied. The luminescent dynamics analysis results indicated that, on UV UC emissions of Gd^3＋ , Yb^3＋ ions served as primary sensitizer ions successively transferring energy to Tm^3＋ to populate the ^3P2 level. Then, Tm^3＋ ions served as secondary sensitizer ions transferring energy to populate the multiple ^6Ij states of Gd^3＋3P2→^3H6 （Tm^3＋ ） ： ^8S7/2→^6IJ（Gd^3＋ ）. Further, ^6DJ levels were populated through other energy transfer processes between Gd^3＋ and Yb^3＋ or Tm^3＋. Finally, UV UC emissions from the excited ^6D9/2, ^6IJ, ^6P5/2, and ^5P7/2 states to the ground state ^8S7/2 were observed. Meanwhile, Tm^3＋ acted as activator in its own UC emissions, and the article did not put emphasis on those except the ^3P2 and ^1I6 levels to the ground state ^3H6 transitions. Especially, the dependences of UV UC emissions of Gd^3＋ on the Yb^3＋ concentrations, the Tm^3＋ concentrations, the annealing temperatures, and the excitation power densities of the 980 nm semiconductor continuous wave laser diode were studied, too.