Chen Baojiu

Reddish Orange Long-Lasting Phosphorescence in KY3F10:Sm3+ for X-Ray or Cathode Ray Tubes

We report a reddish orange long-lasting phosphor of KY3F10:Sm3+ synthesized by a solid-state reaction for applications in x-ray or cathode-ray tubes. The spectrum contains a group of reddish orange emission lines originating from 4G5/2 → 6HJ transitions of Sm3+. The Judd—Ofelt theory is introduced to analyze the optical transitions of the Sm3+ ions. Moreover, phosphorescence characteristics are discussed. The energy charging and release processes of the phosphor are measured and the phosphorescence decay time with 10% of initial intensity is about 40.7 seconds. The order of kinetics and the activation energy are obtained according to the thermoluminescence curve. The phosphorescence mechanism is proposed based on structural analysis and thermoluminescence glow curve measurement.

Optimum fluorescence emission around 1.8 mu m for LiYF4 single crystals of various Tm3+-doping concentrations

In this paper, optical spectra of LiYF4 single crystals doped with Tm3+ ions of various concentrations are reported. The emission intensity at 1.8 mu m first increases with increasing Tm3+ concentration, and reaches a maximum value when the concentration of Tm3+ is about 1.28 mol%, then it decreases rapidly as the concentration of Tm3+ further increases to 3.49 mol%. The emission lifetime at 1.8 mu m also shows a similar tendency to the emission intensity. The maximum lifetime of 1.8 mu m is measured to be 17.68 ms for the sample doped with Tm3+ of 1.28 mol%. The emission cross section of F-3(4) level is calculated. The maximum reaches 3.76 x 10(-21) cm(2) at 1909 nm. The cross relaxation (H-3(6), H-3(4) -> 3F(4), F-3(4)) between Tm3+ ions and the concentration quenching effect are mainly attributed to the change of emission with Tm3+ concentration. The largest quantum efficiency between Tm3+ ions is estimated to be similar to 147% from the measured lifetime and calculated radiative lifetime. All the results suggest that the Tm3+/LiYF4 single crystal may have potential applications in 2 mu m mid-infrared lasers.

2.0-μm emission and energy transfer of Ho3+/Yb3+ co-doped LiYF4 single crystal excited by 980 nm*

Ho3+/Yb3+ co-doped LiYF4 single crystals with various Yb3+ concentrations and ~ 0.98 mol% Ho3+ concentration are grown by the Bridgman method under the conditions of taking LiF and YF3 as raw materials and a temperature gradient (40 °C/cm–50 °C/cm) for the solid–liquid interface. The luminescent performances of the crystals are investigated through emission spectra, infrared transmittance spectrum, emission cross section, and decay curves under excitation by 980 nm. Compared with the Ho3+ single-doped LiYF4 crystal, the Ho3+/Yb3+ co-doped LiYF4 single crystal has an obviously enhanced emission band from 1850 nm to 2150 nm observed when excited by a 980-nm diode laser. The energy transfer from Yb3+ to Ho3+ and the optimum fluorescence emission around 2.0 μm of Ho3+ ions are investigated. The maximum emission cross section of the above sample at 2.0 μm is calculated to be 1.08×10−20 cm2 for the LiYF4 single crystal of 1-mol% Ho3+ and 6-mol% Yb3+ according to the measured absorption spectrum. The high energy transfer efficiency of 88.9% from Yb3+ to Ho3+ ion in the sample co-doped by Ho3+ (1 mol%) and Yb3+ (8 mol%) demonstrates that the Yb3+ ions can efficiently sensitize the Ho3+ ions.

On the fluorescence enhancement mechanism of Er3+ in germanate glass containing silver particles

The spectral properties of trivalent erbium ions (Er3+) are systematically studied in a melt-quenched germanate glass (60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O) containing silver (Ag) particles. Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles. The fluorescence from Er3+ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar+ laser. A comparison is made between a spectral study performed on the unannealed Er3+-doped sample and the one annealed for 20 min. The data of absorption cross section and Judd—Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles, indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er3+ ions. The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.

Ba 3 Gd(PO 4 ) 3 :Eu 3+ 荧光粉的合成及发光性质

采用高温固相反应法合成了不同Eu 3+ 掺杂浓度的Ba 3 Gd(PO 4 ) 3 荧光粉。利用X射线衍射对产生的晶体结构进行了分析, 证实产物为纯相, Eu 3+ 的引入没有导致晶体结构的改变。利用Van Uitert模型对 5 D 0 能级荧光的浓度猝灭行为进行了研究, 发现浓度猝灭是由于Eu 3+ 间交换相互作用所导致。分析了 5 D 0 荧光发射的温度依赖, 给出了荧光温度猝灭行为符合横向穿越模型, 并通过非线性拟合获得了激活能。利用Eu 3+ 的发射光谱和荧光衰减数据, 计算了 5 D 0 - 7 F J 辐射跃迁速率及荧光分支比, 同时得到了光学跃迁强度参数。