Quenching Photoluminescence of Eu(III) by Cu(II) in ZnO:Eu3++Cu2+ Compounds by Solution Combustion Method

In this study Cu2++Eu3+ co-doped ZnO(ZnO/Cu2++Eu3+) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea;the Cu2+ concentrations were 0, 1, 2, 3, 10, and 20 %Wt;the Eu3+ ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu2++Eu3+doped ZnO, at high Cu2+ doping CuO and Eu2CuO4 phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu2+ ions suppress the Eu3+ ion photoluminescence (PL) by means of an overlap mechanism between Cu2+ absorption band and Eu3+emission band (e.g. 5D0→7F2) of the Eu3+ emission spectra.

Effects of two strategies on afterglow behavior of Lu_(2)O_(3):Eu single crystal scintillator:Co-doping with Pr^(3+)and solid solution with Sc_(2)O_(3)

In this paper,effect of two strategies on afterglow behavior of Lu_(2)O_(3):Eu single crystal scintillato r,Pr^(3+)codoping and solid solution with Sc_(2)O_(3),were studied systematically.Two groups of Lu_(2)O_(3):5 at%Eu,x at%Pr(x=0,0.2,0.5,1,2 and 5)and(Lu1-yScy)_(2)O_(3):5 at%Eu(y=0,20 at%,50 at%and 70 at%)single crystals were grown by floating zone(FZ)method in air atmosphere.The structures of as-grown crystals were determined by X-ray diffraction(XRD).The scintillation,photoluminescence properties and carrier trap states were investigated through afterglow,X-ray excitation luminescence(XEL),transmittance,photoluminescence excitation(PLE)and photoluminescence(PL),PL decay and thermal stimulated luminescence(TSL)curves.It is found that with the increase of Pr^(3+)concentration,the afterglow level of the system decreases at the expense of scintillation luminescence efficiency.Meanwhile,although Sc_(2)O_(3):Eu presents much lower afterglow intensity than Lu_(2)O_(3):Eu,the addition of Sc_(2)O_(3)will just increase the afterglow level of the(Lu1-yScy)_(2)O_(3):5 at%Eu single crystal system.Possible mechanisms for above phenomena are discussed based on experimental results.

Y/Eu co-doped TiO_2: synthesis and photocatalytic activities under UV-light

Y and Eu co-doped nano-TiO2 photocatalysts were successfully prepared via a sol-gel method and characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, ultraviolet-visible spectrophotometry（UV-vis）, photoluminescence（PL） and Fourier transform infrared（FT-IR） spectra. Experimental results indicated that Y and Eu doping inhibited the growth of crystalline size and the transformation from anatase to rutile phase and had the function of reducing particle reunion. At the same time, co-doping could also enhance the absorption in visible region and then narrowed the band gap. The photocatalytic activities of the samples were evaluated by the degradation of methylene blue（MB） under ultraviolet（UV） light irradiation, which showed much enhanced photocatalytic activities over un-doped TiO2. The degradation rate of 1.5% Y/Eu-TiO2 of methylene blue was 86%, which was about 5 times of that of un-doped TiO2, and the possible reasons for the improvement of photocatalytic activities were analyzed. In this experiment, the dopant amount of rare earth was 1.5% and the ratio of Y：Eu was 2：3 for the maximum photocatalytic degradation, and the sample calcined at 500℃ showed the best reactivity. For the best samples above, the removal rate of phenol under visble light was 53% whthin 2 h.

Eu2+- Mn2+共掺T相硅酸盐荧光粉的制备与发光性能

荧光粉是新一代照明器件的重要组成部分, T相碱土金属硅酸盐荧光粉具有独特的晶体结构,表现出优良的抗发光热猝灭性能。将Mn^2+引入具有青绿色发光的(Ba0.7Ca0.29Eu0.01)2SiO4荧光粉,通过Eu^2+-Mn2+能量传递可以实现Mn^2+的红光发射。通过高温固相反应法制备了具有不同Mn含量的T相碱土金属硅酸盐荧光粉(Ba0.7Ca0.29-zEu0.01Mnz)2SiO4。X射线衍射(XRD)图谱表明,所合成的样品都为纯相,晶格常数随Mn2+含量增多而减小。通过稳态荧光发射光谱、激发光谱和荧光衰减曲线研究Eu^2+-Mn^2+能量传递过程,确认其机制为电多极作用,临界距离为3.433 nm。T相(Ba0.7Ca0.29-zEu0.01Mnz)2SiO4荧光粉在200℃时的发光强度仍可保持室温时的67%~80%,抗发光热猝灭性能优异。通过改变Mn的含量,可以调控Eu^2+的蓝光峰与Mn^2+的红光峰之间的相对比例,从而实现从冷白光到暖白光的单一基质白光发射。