第一性原理研究稀土掺杂ZnO结构的光电性质

基于密度泛函理论的第一性原理平面波超软赝势方法,运用Castep计算分析了Er, Gd两种稀土元素掺杂的ZnO结构, 对本征ZnO和掺杂晶体的能带结构、态密度以及光学性质进行了分析对比. 由掺杂前后的结果分析发现,稀土掺杂的ZnO结构引入了由稀土原子贡献的导电载流子, 增强了体系的电导率, 费米能级上移进入导带. 研究表明由于稀土元素的掺入, ZnO结构在费米能级附近出现了杂质能带, 这是由稀土的4f态电子所形成. 同时, 纯净ZnO与Er-ZnO, Gd-ZnO和(Er, Gd)-ZnO的介电函数虚部有明显的差异. 在光学性质上, 掺杂ZnO在可见光区的吸收系数和反射率都比纯净ZnO高, 能量损失峰出现红移现象. 关键词： ZnO 稀土 掺杂 第一性原理     

Raman spectra of soda-lime-silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared by the traditional melting-quenching methods. In order to reveal the effects of rare earth elements on the behavior of soda-lime-silicate glass the structures of soda-lime-silicate glasses doped with different rare earth oxides were determined using an INVIA confocal microRaman spectrometer equipped with a CCD detector, and viscosities of glass melts were measured using a rotating crucible viscometer; the melting temperature of the studied glasses was derived on the basis of the Arrhenius equation. Three expressions of the fraction of non-bridging oxygen (NBO/NBO+BO), average number of non-bridging oxygen (NBO) per tetrahedron (NBO/tetrahedron) and average number of bridging corners per tetrahedron (bridges/tetrahedron) for investigated soda-lime-silicate glasses were given, and the effect of rare earth dopants on the structure of soda-lime-silicate was characterized by the Raman shift, variation of the [SiO₄] tetrahedron structural unit Qⁿ (n=1,2,3,4), fraction of non-bridging oxygen and the average number of bridging corners per tetrahedron. The effect of doping rare earth oxides into glass on the viscosity and melting temperature was interpreted by changes in structure of soda-lime-silicate glasses doped with rare earth oxides.     

Structure and properties of soda lime silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare-earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides.     

稀土掺杂材料的上转换发光

稀土掺杂材料的上转换发光是实现光波频率转换的重要途径,也是稀土掺杂发光材料研究的重要内容。本文从介绍与上转换相关的基本概念出发,阐述了稀土离子上转换发光的发展历史;对稀土离子掺杂材料的能量传递、激发态吸收、合作敏化、合作发光、双光子吸收激发及光子吸收雪崩等上转换发光机制进行了概述,并对各机制进行了比较;对不同稀土离子掺杂体系中上转换发光的机制进行了总结;对以往研究的稀土掺杂上转换发光材料的基质,包括粉体材料、晶体材料、非晶材料进行了概括;最后对影响稀土离子上转换发光效率的因素进行了分析,提出了在上转换发光材料的设计中应重点考虑基质对泵浦光及上转换发射光的吸收、基质材料的声子能量、稀土离子的掺杂方案及泵浦途径等因素。     

Structural and magnetic property of Mn:ZnO bulk ceramic doped with rare earth (Gd/Sm) atoms

This paper reports the paramagnetic behavior of Mn doped ZnO co-doped with rare earth (Gd and Sm) atoms. The formation of secondary rare earth oxides (Gd₂O₃ and Sm₂O₃) is confirmed from the X-ray diffraction patterns. The rare earth oxides in the system forbids the grain growth and interconnection between the grains. The weak link between the grains suppresses the long range exchange interaction between the Mn ions and hence, reduces the ferromagnetic ordering. Owing to the large mismatch between ionic radii of rare earth and transition metal atoms inside the matrix, the rare earth element cannot contribute to promote ferromagnetic behavior in Mn doped ZnO, irrespective of their high individual magnetic moments.     

Valence of “divalent” rare earth metals

It is generally recognized that light rare earths change their valence from 2 to 3 when forming a bulk metal while remaining divalent at the surface. However, performed DFT calculations ultimately indicate that the higher-binding-energy peaks in photoemission spectra (like the −5.3 eV peak for Sm), characteristic of the trivalent 4fⁿ⁻¹5d¹ configuration, correspond not to the ground state, but to excited states induced by radiation. This means that the trivalent state is not inherent for the bulk of divalent rare earths, and therefore they do not become trivalent.     

Some optical properties of rare earth (Dy,Nd and Sm) activated ZnO phosphors

Some rare earth (Dy, Nd and Sm) doped ZnO electroluminors have been prepared in vacuum (1 torr) and their photo (PL) and electroluminescence (EL) spectra investigated at room temperature at different concentrations of rare earth (RE) ions. Compared to the spectra of undoped ZnO, these spectra consist of the same bands shifted either towards low or high energy side and the intensity of high energy band is decreased while that of low energy band is enhanced. In any case no additional band or line was observed. The experimental results have been explained on the basis of donor-acceptor pair model of recombination process where donor levels are due to RE ions and the acceptors are the luminescent centres of undoped ZnO electroluminors. The mechanism of excitation is of acceleration-collision type.     

不同价态稀土元素Yb掺杂ZnO的电子结构和光学性质

基于密度泛函理论, 采用第一性原理平面波超软赝势法, 对六方纤锌矿结构的ZnO晶体和Yb²⁺, Yb³⁺分别掺杂ZnO晶体进行几何优化, 并在此基础上计算得到了未掺杂ZnO晶体及不同价态Yb元素掺杂ZnO体系的空间结构、 能带、电子态密度及光学性质.结果表明: 掺杂后体系形成能减少, 稳定性增加, 并引入了Yb-4f杂质能级. 掺杂不同价态的Yb元素对能带结构产生了不同的影响, 并且都使体系的光学性质发生了明显变化.与纯ZnO相比, Yb²⁺, Yb³⁺ 分别掺杂ZnO体系的介电函数虚部在0.46 eV处均出现新峰, 静态介电函数明显增大, 吸收带边均红移, 并在0.91 eV处出现较强吸收峰, 对产生这一现象的原因给出了定性的讨论. 关键词： 掺杂 ZnO 不同价态 第一性原理     

稀土元素(Y,La)掺杂ZnO的电子结构和光学性质

采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了未掺杂ZnO和稀土(Y,La)掺杂ZnO体系的空间结构、能带、电子态密度与光学性质.结果表明,掺杂后体系的形成能减小,稳定性变强,带隙展宽,费米能级进入导带中,体系呈金属性,载流子发生简并,形成简并半导体.定性分析了掺杂后光学性质的变化. 关键词： 氧化锌 掺杂 第一性原理     

香兰素对甲苯胺希夫碱稀土配合物的红外光声光谱

研究了香兰素对甲苯胺希夫碱及其金属配合物在３８００－２００ ｃｍ＾－１范围的傅里叶变换红外光谱光谱，对主要谱带进行了经验归属。     

Magnetic property improvement of niobium doped with rare earth elements

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium.Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.     

过渡金属掺杂ZnO的电子结构和光学性质

利用基于密度泛涵理论的超软赝势法(USPP)，结合局域密度近似(LDA)，对过渡族金属离子掺杂的纤锌矿型ZnO做第一性原理计算，得到了它的平衡晶格常数、结合能、电子态密度分布、能带结构、介电函数、光学吸收系数等性质，详细讨论了掺杂后ZnO化合物的电子结构及成键情况，并结合实验结果定性分析了掺杂后光学性质的变化. 关键词： 氧化锌 掺杂 第一性原理 光学性质     

稀土掺杂BAP玻璃的制备及性能研究

采用UVPC和DSC等测试手段系统研究了稀土Sm2O3掺杂BaO-Al2O3-P2O5(BAP)激光防护玻璃的光谱性能及析晶性能。结果表明:吸收光谱的特征吸收峰强度随Sm2O3含量的增加逐步增强,吸收谱线向两端非均匀展宽,玻璃在1075nm波长处的光密度与稀土含量近似成线性关系,当Sm2O3含量达到17.5mol%时,透过率T<0.03%;随着稀土含量的增加,玻璃的析晶参数β先增后减,玻璃的析晶倾向也随之先下降而后提高,BaO/Al2O3比值的降低可使玻璃的形成能力提高。     

高压下制备的透明低阻n-ZnO陶瓷的表征

本文报道了高压烧结透明低阻ZnO陶瓷的过程,解决了常压下烧结ZnO高阻不透明的问题.在5 GPa,800℃下获得了最佳光电性能的低阻透明ZnO陶瓷,其透过率为49%左右,电阻率为0.57 Ω ·cm,禁带宽度为3.31 eV,载流子浓度为8.36×10¹⁷ cm^-3,迁移率为23 cm² ·V^-1 ·s^-1,良好的n型导电性来自于Zn_i和V_o关键词： 高压 陶瓷 n-ZnO 透明     

Binding of rare earth metal complexes with an ofloxacin derivative to bovine serum albumin and its effect on the conformation of protein

The water-soluble Pr (Ⅲ) and Nd (Ⅲ) complexes with an ofloxacin derivative have been prepared and characterized. The single-crystal X-ray diffraction showed that the Pr (III) and Nd (III) complexes have the similar molecular structure. Under physiological pH condition, the effects of [PrL(NO₃)₂(CH₃OH)](NO₃) and [NdL(NO₃)₂(CH₃OH)](NO₃) on bovine serum albumin (BSA) were examined using fluorescence spectroscopy in combination with UV-vis absorbance and circular dichroism (CD) spectra. The result reveals that the quenching mechanism of fluorescence of BSA by two complexes is a static quenching process and the number of binding sites is about 1 for both. The thermodynamic parameters (ΔH=−14.52 kJ mol⁻¹, ΔS=56.54 J mol⁻¹ K⁻¹ for [PrL(NO₃)₂(CH₃OH)](NO₃) and ΔH=−24.63 kJ mol⁻¹, ΔS=22.07 J mol⁻¹ K⁻¹ for [NdL(NO₃)₂(CH₃OH)](NO₃)) indicate that hydrophobic and electrostatic interactions are the main binding force in the complexes-BSA system. The binding average distance between complexes and BSA was obtained on the basis of Förster's theory. In addition, it was proved by the CD spectra that the BSA secondary structure was changed in the presence of complexes in an aqueous solution.     

Effect of varying lanthanide local coordination sphere on luminescence properties illustrated by selected inorganic and organic rare earth complexes synthesized in sol-gel host glasses

Inorganic and organic ligands were carefully selected to illustrate the effect of modifications in the local field environment around the rare earth lanthanide (III) on its emission properties. In this article two strategies were employed to enhance emission of lanthanides encapsulated in sol-gel glass. (i) Changing the symmetry around the lanthanide, which was diagnosed by changing the local environment around the lanthanide using different inorganic counter ions (acetate, nitrate and chloride) these ligands differ in their affinity toward the lanthanide first coordination sphere. The ligand that penetrates the lanthanide more results in more asymmetric environment and thus results in higher emission. The aim of this part was to demonstrate the change of symmetry on emission in the absence of energy transfer. Our results indicate that the acetate ion has the highest affinity toward the first coordination sphere followed by the nitrate while the chloride showed the lowest affinity. Penetration by the ligands ofthe lanthanide also results in removing OH quenchers surrounding the lanthanide and this further explains the boost in emission. (ii) A bulky organic ligand that forms a complex with the lanthanide is used. The organic ligand separates the lanthanide ion from inner O-H oscillators. In this case the chelating organic chromophore with suitable photophysical properties was employed to sensitize the lanthanide and thus energy transfer occurs via the antenna effect. The organic ligand absorbs UV light, then energy is transferred to the lanthanide and finally the lanthanide emits in the visible region. The first coordination environment surrounding europium was controlled by the ligand selection and the outer sphere was modified by doping the synthesized complexes in an optically transparent sol-gel glass host. The glass network carefully prepared by sol-gel process is effective in preventing free oxygen and water from attacking lanthanide -complexes without loss of luminescence. Emission spectroscopy measurements of the doped silica specimens confirmed the variation of Eu (III) emission depending on the first coordination sphere surrounding the europium ion. The encapsulation of the europium complexes was performed for two reasons: (i) to improve the stability of red phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (ii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light.     

脉冲强磁场下稀土材料的发光行为研究

脉冲强磁场具有峰值磁场强及扫场速度快的特点,在一个磁场脉冲内可获得从零场到最高磁场强度的全部数据,因而测量结果具有较高的精确度和对比度。稀土发光材料因具有发光谱线丰富、发光效率高的特点,在照明、显示和传感等领域有着广泛的应用。在强磁场作用下,稀土发光材料展现出发光强度和颜色可调的特征,在磁场传感、磁场标定和磁控发光器件等方面有重要应用价值。文章利用武汉国家脉冲强磁场科学中心磁光测量装置,系统地研究了铒、铕等稀土元素掺杂的发光材料在脉冲强磁场作用下的发光光谱、发光强度以及精细能级结构等特征随磁场变化的规律,初步探索了脉冲强磁场下的磁光谱在晶体结构分析、能级结构确定、磁场标定以及磁场传感等方面的应用。     

稀土合金RCo5中稀土离子的磁晶各向异性

利用单粒子点电荷模型研究了RCo5中一系列稀土离子,包括轻离子Pr3+,Nd3+和重离子Tb3+,Dy3+,Er3+的磁晶各向异性.计算分析表明过渡族元素对晶场的贡献和晶场高阶项不可忽略, 虑及过渡族元素和晶场高阶项对晶场的贡献后,得到的各稀土离子的磁晶各向异性常数及其随温度变化都与实验一致的结果,此结果还特别解释了以前不能解释的轻稀土离子Pr3+的易锥向取向.     

Rapid synthesis and luminescence of the Eu, Er codoped ZnO quantum-dot chain via chemical precipitation method

ZnO quantum-dot chains codoped with Eu³⁺ and Er³⁺ were synthesized by the chemical precipitation method and the codoping effects on the structures, morphologies and optical properties of the powders were briefly investigated. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results indicated the Eu³⁺ and Er³⁺ were incorporated into the crystal lattice of ZnO host. Transmission electron microscope (TEM) measurements showed the sizes of the ZnO quantum dots decreased with the increase of Eu³⁺ and Er³⁺ doping concentration, and the quantum-dot chains were formed by codoping with Eu³⁺ and Er³⁺. The green emissions in the photoluminescence spectra were attributed to 4f-4f of Er³⁺ inner shell ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions, and the characteristic red emissions of Eu³⁺ ions were attributed to the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, respectively. Moreover, the red emission of the Eu³⁺ ions gradually decreased with the Er³⁺ ions doping concentration increased, which may be due to the different energy storage centers in the powders.