Bi~(3+)掺杂对Y_2WO_6:Nd~(3+)/Yb~(3+)的近红外发光的敏化

采用高温固相法合成了Y_2WO_6:Nd~(3+)/Yb~(3+)及Y_2WO_6:Nd~(3+)/Yb~(3+),Bi~(3+)系列近红外发光材料,研究了其晶体结构、发光性能、荧光寿命,并讨论了Bi~(3+)的掺入对其近红外发光的敏化作用。Bi~(3+)的掺入不仅显著增强了样品中Nd~(3+)/Yb~(3+)的特征近红外发光强度,还使Y_2WO_6:Nd~(3+)/Yb~(3+)的激发光谱红移。随着Nd~(3+)/Yb~(3+)浓度的升高,Bi~(3+)的荧光寿命逐渐变短,表明样品中存在Bi~(3+)到Nd~(3+)/Yb~(3+)的能量转移。Nd~(3+)和Yb~(3+)的浓度为9%时,能量传递效率分别为85%,88%。根据Inokuti-Hirayama(I-H)理论模型分析表明Bi~(3+)到Nd~(3+)/Yb~(3+)的能量传递为电偶极矩-电偶极矩相互作用。因此,Y_2WO_6:Nd~(3+)/Yb~(3+),Bi~(3+)可作为一种光谱转换材料,有望提高硅太阳能电池的光电转换效率。     

Yb~(3+)共掺杂La_2Sn_2O_7:Er~(3+)上转换发光材料的水热合成与性能

利用水热法合成Yb~(3+)共掺杂La_2Sn_2O_7:Er~(3+)上转换发光材料,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、紫外可见漫反射光谱(UV-Vis)和上转换发光光谱(UPL)对Yb~(3+)掺杂量对合成样品的上转换性能及反应体系pH对合成样品的物相结构进行分析。结果表明,反应体系的pH和Yb~(3+)掺杂量分别影响着所制备样品的物相结构和上转换性能。反应体系pH为13的水热环境下制备的样品为单一相烧绿石结构的La_2Sn_2O_7样品。上转换图谱分析结果表明,所制备的Yb~(3+)共掺杂La_2Sn_2O_7:7%(原子分数)Er~(3+)在980 nm的近红外光激发下在529, 550和665 nm处分别出现了Er~(3+)的上转换发射特征峰,并对Yb~(3+)共掺杂La_2Sn_2O_7:7%Er~(3+)样品的上转换敏化发光机制进行了分析,其中位于529 nm处的绿色光发射属于双光子吸收发光机制,且当Yb~(3+)掺杂量高于14%时观察到浓度猝灭现象。     

NaYF_4:Yb~(3+)/Sm~(3+)的水热合成及980 nm激发下的光致发热

本文利用简单的水热法制备了NaYF_4:Yb~(3+)/Sm~(3+)光加热器,并基于可靠的上转换发光温度计研究了它在980 nm辐射下的光热转换特性.为了克服激光辐射所引起的热效应,间断的光谱扫描方式用来研究NaYF_4:Yb~(3+)/Sm~(3+)光热转换与泵浦功率密度的关系.结果显示,激光辐射点的温度与泵浦功率密度线性相关.更有趣的是,我们注意到光热响应度依赖于Yb~(3+)掺杂浓度.95%Yb~(3+)掺杂在低功率密度下显示最强的光致发热量,但60%Yb~(3+)掺杂对应最大的光热响应度(373(K mm~2)/W).可能的原因在于高浓度Yb~(3+)掺杂有利于980 nm光子的吸收,但Yb~(3+)之间长距离的能量转移抑制Yb~(3+)到Sm~(3+)的能量传递,进而降低了光热响应度.     

Yb~(3+)-Tb~(3+)共掺杂β-NaYF_4纳米晶的上转换发光特性研究

采用水热合成法,以油酸作乳化剂成功制备了Yb~(3+)-Tb~(3+)共掺杂β-NaYF_4纳米晶。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和荧光光谱仪对所制备的样品进行表征。在980 nm红外半导体激光器的激发下,不仅观察到Yb~(3+)/Tb~(3+)共掺杂NaYF_4纳米晶对应于Tb~(3+)离子5D3→7FI(I=6,5和4)和5D4→7FI(I=6,5,4和3)能级跃迁从红色到紫外的上转换荧光,同时还观察到了杂质离子Er~(3+)的发光。实验发现随着Yb~(3+)浓度的相对减小和Er~(3+)浓度的相对增大,489 nm对应于Tb~(3+)离子5D4→7F6能级跃迁的上转换蓝光得到增强。在Yb~(3+)-Tb~(3+)-Er~(3+)系统中,简要地讨论了从Yb~(3+)到Er~(3+)再到Tb~(3+)的能量传递过程。     

Yb~(3+)/Er~(3+)共掺Gd_2Mo_3O_(12)的强绿色上转换发光及温度传感特性

采用固相反应法合成了Gd_2Mo_3O_(12):x%Yb~(3+)/1%Er~(3+)(x=0,2,5,10,20)荧光粉。当Yb~(3+)浓度超过5%,Yb~(3+)-MoO_4~(2-)二聚体形成并发挥敏化作用;当Yb~(3+)浓度达20%,二聚体敏化主导上转换发光。由于二聚体敏化抑制红光发射,成功获得高强度的绿色上转换发光。结合反射谱、拉曼谱、下转换谱、上转换功率关系、二聚体模型和三能级模型,详细讨论了这种和Yb~(3+)浓度有关的上转换发光。另外,基于两个绿光发射带的相对强度比,探究了最佳样品在300~500K范围内的温度传感特性,证实Gd_2Mo_3O_(12):Yb~(3+)/Er~(3+)在温度传感方面具有潜在应用价值。     

GdAlO_3:Er~(3+)/Yb~(3+)/Tm~(3+)上转换荧光粉的制备与发光性能表征

采用NH4HCO3共沉淀法合成了单相的钙钛矿(Gd AlO 3:Er~(3+)/Yb~(3+)/Tm~(3+))纳米荧光粉体,并用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱仪(FR-IR)、荧光发射光谱对荧光粉体(Gd AlO 3:Er~(3+)/Yb~(3+)/Tm~(3+))进行表征。结果表明:使用NH4HCO3共沉淀法比传统的固相法制备发光体系所需的煅烧温度更低,而且能够得到分散均匀的、颗粒大小一致的纳米荧光粉。在980 nm波长激发下,掺杂Er~(3+)/Yb~(3+)的Gd AlO 3荧光粉体系得到524,546(绿光)与659 nm(红光)的上转换发射光谱,且红光比例随着Er~(3+)和Yb~(3+)的掺杂浓度增加而不断增加,并对其能量传递机制进行了分析;最后,通过添加Tm~(3+)离子,在荧光粉(Gd AlO ~(3+)3:Er~(3+)/Yb~(3+)/Tm)体系中调节三种稀土离子的掺杂浓度,得到了较理想的复合白光。     

稀土离子水解聚合作用的研究(Ⅳ) Yb~(3+)的水解聚合作用

稀土离子的水解和聚合作用是稀土元素的重要性质之一,与其分离、分析及应用有密切的关系。我们已对Pr~(3+)、Sm~(3+)、Gd~(3+)、Eu~(3+)等离子的水解聚合作用进行了研究,得到一些新的结果。等认为Yb~(3+)水解只生成单核离子Yb(OH)~(2+)。等发现Yb~(3+)可聚合生成Yb_2(OH)_2~(4+)。本研究发现,除上述两种离子外,还有     

NaGd(WO_4)_2:Yb~(3+),Ho~(3+),Nd~(3+)纳米晶的水热合成及发光性质研究

采用水热法制备了Yb~(3+),Ho~(3+),Nd~(3+)离子共掺杂的钨酸钆钠纳米晶(NaGd(WO_4)_2:Yb~(3+),Ho~(3+),Nd~(3+)),并在800℃进行了热处理。分别采用X射线衍射(XRD)、场发射扫描电镜(SEM)和荧光光谱仪(PL)对纳米晶的晶体结构、微观形貌和上转换发光性质进行了表征。XRD结果显示样品属于四方晶系、白钨矿结构。SEM图谱表明所得纳米晶具有较好的分散性,颗粒大小约为50 nm。在980 nm激光激发下,NaGd(WO_4)_2:Yb~(3+),Ho~(3+),Nd~(3+)纳米晶发出546 nm的绿光与660 nm红光,分别对应Ho~(3+)离子的~5F_4,~5S_2→~5I_8和~5F_5→~5I_8能级跃迁。当Nd~(3+)离子掺杂浓度为0.5%(摩尔分数)时,纳米晶的发光强度最大。随着Nd~(3+)离子掺杂量的增加,红光与绿光的相对强度比逐渐减小,纳米晶的光谱由橙色光向黄色光区域变化。本文对NaGd(WO_4)_2:Yb~(3+),Ho~(3+),Nd~(3+)纳米晶的光谱调控和上转换发光机制进行了研究。     

水热合成LuF_3∶Yb~(3+),Er~(3+)微晶及其上转换发射与温度传感特性（英文）

通过在不同pH值下的简易水热法合成不同Yb~(3+)离子(n_(Yb~(3+))/n_(Lu~(3+))=5%~15%)和Er~(3+)离子(n_(Er~(3+))/n_(Lu~(3+))=1%~5%)掺杂浓度的LuF_3∶Yb~(3+),Er~(3+)微晶荧光粉。发现pH值对正交相LuF_3∶Yb~(3+),Er~(3+)的合成起着关键作用。在980nm激发下,LuF_3∶Yb~(3+),Er~(3+)荧光体呈现出以523nm(~2H_(11/2)→~4I_(15/2))和539nm(~4S_(3/2)→~4I_(15/2))为中心的强绿光上转换(UC)发射以及以660nm(~4F_(9/2)→~4I_(15/2))为中心弱红光上转换发射。通过使用X射线衍射(XRD)和光致发光(PL)分析测定了最强发射强度的Er~(3+)和Yb~(3+)的最佳掺杂浓度。浓度依赖性研究表明,达到最强的绿光上转换发光时最佳掺杂浓度为10%Yb~(3+),2%Er~(3+)。通过改变泵浦功率来研究LuF_3∶Yb~(3+),Er~(3+)荧光粉UC发光机制。通过980nm二极管激光器在293~573K的范围内研究了在523和539nm处的2个绿光UC发射带的荧光强度比(FIR)的温度依赖性,发现在490K得到最大灵敏度约为15.3×10~(-4)K~(-1)。这表明LuF_3∶Yb~(3+),Er~(3+)荧光体可应用于具有高灵敏度的光学温度传感器。     

Er~(3+)-Yb~(3+)掺杂SiO_2-SrO-NaF玻璃陶瓷的制备及表征

采用熔融晶化法制备了主晶相为SrF_2的Er~(3+)-Yb~(3+)共掺透明氟氧化物玻璃陶瓷,利用DSC、XRD、SEM、UV-Vis-NIR和荧光光谱对样品的结构、形貌、发光性能进行了测试与表征。研究表明:该体系玻璃最佳热处理温度为620℃,最佳热处理时间为2h,并讨论了Yb~(3+)不同掺杂浓度对Er~(3+)-Yb~(3+)共掺玻璃陶瓷样品上转换发光性能的影响,确定Er~(3+)-Yb~(3+)最佳掺杂浓度比为1∶7,同时观察到了明亮的绿光(522,540 nm)和较弱的红光(656 nm),对Er~(3+)和Yb~(3+)之间的能量传递过程进行了讨论。     

静电纺丝技术制备Y_2O_3∶Yb~(3+),Er~(3+)上转换纳米纤维及其表征

采用静电纺丝技术制备了PVA/[Y(NO3)3+Yb(NO3)3+Er(NO3)3]复合纳米纤维,将其在适当的温度下进行热处理,得到Y2O3∶Yb3+,Er3+上转换纳米纤维.XRD分析表明,复合纳米纤维为无定形,Y2O3∶Yb3+,Er3+上转换纳米纤维属于体心立方晶系,空间群为Ia3.SEM分析表明,复合纳米纤维的平均直径约为150nm;随着焙烧温度的升高,纤维直径逐渐减小.经过600℃焙烧后,获得了直径约60nm的Y2O3∶Yb3+,Er3+上转换纳米纤维.TG-DTA分析表明,当焙烧温度高于600℃时,复合纳米纤维中水分、有机物和硝酸盐分解挥发完毕,样品不再失重,总失重率为83%.FTIR分析表明,复合纳米纤维与纯PVA的红外光谱一致,当焙烧温度高于600℃时,生成了Y2O3∶Yb3+,Er3+上转换纳米纤维.该纤维在980nm的半导体激光器激发下发射出中心波长为521,562nm的绿色和656nm的红色上转换荧光,分别对应于Er3+离子的2H11/2/4S3/2→4Il5/2跃迁和4F9/2→4Il5/2跃迁.对Y2O3∶Yb3+,Er3+上转换纳米纤维的形成机理进行了讨论.     

Bi3+掺杂对YVO4:Yb3+近红外发光的敏化作用

用主温固相法合成了Yb³⁺、Bi³⁺共掺的YVO₄,研究了Bi³⁺的掺入对YVO₄:Yb³⁺发光光谱的影响和近红外发光的敏化作用.X射线衍射图谱研究表明:掺入Yb³⁺、Bi³⁺之后,基质YVO₄的晶格结构没有发生明显变化.Bi³⁺的掺入不仅显著增强了样品中Yb³⁺的特征远红外发光强度,还使YVO₄:Yb³⁺激发光谱的范围红移,当Bi³⁺掺入的摩尔分数从0增加到0.05时,样品的最强激发峰位置从335nm红移至352 nm,激发光谱范围由300-360 nm扩宽至300-430 nm.优化的Bi³⁺掺入量为0.03.初步讨论了VO₄^3-,Bi³⁺Yb³⁺间的能量传递机理.结果表明Bi^3-的共掺使YVO₄:Yb³⁺样品对长波紫外光的响应性能大大改善,作为一种基于量子剪裁的光谱转换材料,可以更好地匹配太阳光的能量谱,有助于提高硅太阳能电池的光电转换效率.     

Shape Control,Crystalline Conversion and Pseudocapacitance Properties of Mn_3O_4: Effects of Yb~(3+) Doping

We report a facile method for the synthesis of manganese oxide(Mn_3O_4) nanorods via the direct reaction of MnCl2 and H_2 O2 by doping Yb~(3+) ions at room temperature and air atmosphere. The Mn_3O_4:Yb~(3+) samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), cyclic voltammetry(CVs), electrochemical impedance spectroscopy(EIS), and charging-discharging test(CD). The results show that trace Yb~(3+) doping(6 at%) could effectively induce crystalline transformation of Mn_3O_4 from cubic system(space group Fd-3 m) to tetragonal system(space group I41/amd) and incite the morphology changing from irregular particles to uniform nanorods. When Yb~(3+) doping amount is 3%, the capacitance of Mn_3O_4 reaches the maximum, 246 F/g, which is related to the morphology change and the corresponding decrease of impedance.     

Optical Spectroscopic Properties of Yb~(3+)-Doped MgMoO_4 Crystal Grown by the TSSG Method

This paper reports the growth and spectral assessments of Yb~(3+) ion doped MgMoO_4(Yb~(3+):MgMoO_4) crystal grown by the TSSG method. Polarized spectral properties of Yb~(3+):MgMoO_4 crystal, including absorption and emission cross-sections, absorption FWHM and fluorescence lifetime, have been investigated. The laser performance parameters bmin, Isat and Iminhave also been evaluated. All the investigated results show the Yb~(3+)-doped MgMoO_4 crystal is expected as a promising candidate for ultrashort pulse and tunable lasers.     

Color-tunable Upconversion Properties of Tb~(3+)/Er~(3+)/Yb~(3+) Tri-doped Na_5Gd(WO_4)_4 Crystals

In this work, novel phosphors Na5Gd(WO4)4: Tb^3+/Yb^3+ and Na5Gd(WO4)4: Tb^3+/Er^3+/Yb^3+ phosphors were synthesized by the solid state reaction method. The photoluminescence properties were investigated. The introduction of Er^3+ to NGW: Tb^3+/Yb^3+ was used to modify the chromaticity coordinates, then providing a good color tunable property. The change in the chromaticity coordinates induces the shift of emission color from yellow-green to blue-green for NGW: Tb^3+/Er^3+/Yb^3+ as the temperature increases. All the results indicate that the NGW: Er^3+/Tb^3+/Yb^3+ phosphors may be used as optical temperature sensing materials.     

Efficient Near-infrared Down-conversion Phosphor of Ce~(3+)/Yb~(3+) Co-doped La_3Ga_5SiO_(14) and Its Spectral Structural Modulation

A series of near-infrared(NIR) down-conversion phosphors of La_3 Ga_5 SiO_(14)(LGS):Ce~(3+)/Yb~(3+)were synthesized via high-temperature solid-state reaction. Under excitation at 345 nm, the phosphors show strong NIR emission around 978 nm, which matches well with the optimal spectral response of crystalline silicon(c-Si)solar cells. The emission spectra and decay curves were used to demonstrate the energy transfer from Ce~(3+) to Yb~(3+).The energy transfer mechanism was discussed in detail, indicating that the energy transfer from Ce~(3+) to Yb3+ is dominated by a single photon process, and the energy transfer efficiency is up to 51%. In addition, La3 Ga5-zAlzSiO_(14)(z = 0, 1, 2, 3):Ce3+/Yb~(3+) were also synthesized. The NIR emission intensity of La3 Ga2 Al3 SiO14:1%Ce~(3+)/5%Yb~(3+) is 4.6 times that of LGS:1%Ce~(3+)/5%Yb~(3+), and the thermal relaxation was used to explain this phenomenon. The results show that La_3 Ga_(5-z)AlzSiO_(14)(z = 0, 1, 2, 3):1%Ce~(3+)/5%Yb~(3+) phosphors have the potential to increase the conversion efficiency of c-Si solar cells.     

Spectroscopy and Energy Transfer in Yb3＋ and Tm3＋ Co-doped Gd3Ga5O12 Crystal

Yb3+/Tm3+ co-doped Gd3Ga5O12 single crystal with a dimension of Φ30mm×20mm was grown successfully by Czochralski method.The absorption spectrum was recorded at room temperature and used to calculate the absorption cross-section.Based on the Judd-Ofelt(J-O) theory,we obtained the three intensity parameters and spectral parameters of this crystal,such as the line strengths,oscillator strengths,radiative probabilities and radiative lifetimes as well as the fluorescent branching ratios.Room temperature fluorescence spectra and luminescence decay curves were recorded.The energy transfer between Yb3+-Tm3+ was observed and the mechanism was discussed.The stimulated emission cross-section of the 3F4→3H6 transition was calculated by the Füchtbauer-Ladenburg(F-L) equation.The potential laser gains for this transition were also investigated.This crystal is promising as a tunable infrared laser crystal at 2.0 μm.     

A Mixed Metal Phosphate Containing Two Types of Phosphoric Anionic Groups: Cs_2Ga_4(P_2O_7)_2(P_4O_(13))

A new mixed metal phosphate of Cs2Ga4P8O(27), which also can be written as Cs2Ga4(P2O7)2(P4O(13)), was synthesized by high temperature solid state syntheses and structurally characterized by X-ray single-crystal diffraction for the first time. The title compound crystallizes in monoclinic system with space group P21/c(No.14), and features a 3D framework which can be considered as alternating layers of {Ga2(P4O(13))}n and {Ga2(P2O7)2}n^2n- parallel to the bc plane further connected by Ga-O-P linkages, where Cs^+ cations are located in the free space between two adjacent layers to charge the valence. The Ga³⁺ cations in the compound contain two kinds of coordination models(4 and 6). Furthermore, the title compound coexists of two phospho-ric anionic groups which are non-condensed horseshoe-shaped(P4O(13)) and two(P2O7) with different symmetries. The density functional theory calculations indicate that Cs2Ga4P8O(27) is a direct band gap insulator with flat valence and dispersive conduction bands and a band gap of 4.13 eV.     

Emission analysis of Sm(3+) and Dy(3+):MgLaLiSi(2)O(7) powder phosphors

This paper reports on the structural and emission properties of newly synthesized Sm(3+) and Dy(3+):MgLaLiSi(2)O(7) powder phosphors based on the measurement of their XRD, SEM, FTIR and photoluminescence spectra. Emission spectra of the Sm(3+):MgLaLiSi(2)O(7) phosphors with lambda(exci)=402 nm ((6)H(5/2)-->(4)F(7/2)) and Dy(3+):MgLaLiSi(2)O(7) phosphors with lambda(exci)=385 nm ((6)H(15/2)-->(4)I(13/2)) have been analyzed. Emission mechanisms of these phosphors have also been explained.     

980 nm LD激发下稀土掺杂Gd_2Ti_2O_7粉末上转换发光

用高温固相法分别合成了Er~(3+)/Yb~(3+),Ho~(3+)/Yb~(3+),Tm~(3+)/Yb~(3+)离子共掺杂的Gd_2Ti_2O_7粉末,X射线衍射结果表明所制备的粉体为立方相烧绿石结构,TEM电镜照片显示其颗粒平均粒径为3μm.该粉末在980 nm LD激发下,分别发射出中心波长为553 nm绿色和662 nm红色(掺Er~(3+)样品)、545 nm绿色和652 nm红色(掺Ho~(3+)样品)、482 nm蓝色和653 nm红色(掺Tm~(3+)样品)的上转换荧光.上转换发光强度和激发功率的关系研究表明,能量传递和激发态吸收是上转换发光的主要机制.同时对Yb~(3+)-Er~(3+),Yb~(3+)-Tm~(3+)共掺体系的上转换发光强度"过饱和"现象进行了分析,认为是样品的被激发点的温度升高导致了荧光猝灭现象.