掺杂LiNbO3晶体的光折变性能

在LiNbO3中掺进CeO2 ,MnCO3生长Ce∶LiNbO3和Ce∶Mn∶LiNbO3晶体 ,晶体被极化和还原处理。X射线衍射仪测试晶体的晶格常数 ,采用UV -Spectrophotometer测试晶体的吸收光谱。讨论了掺杂离子对晶格常数的影响、掺杂离子在晶体中的占位及使LiNbO3晶体吸收边发生红移的机理。利用二波耦合实验测试了晶体的指数增益系数、衍射效率和响应时间 ,结果表明 :Ce∶Mn∶LiNbO3晶体的最大指数增益系数达到 2 2cm- 1 ,Ce∶LiNbO3晶体的最大指数增益系数为 17cm- 1 ;Ce∶Mn∶LiNbO3和Ce∶LiNbO3晶体的有效载流子浓度分别为 0 .4× 10 1 5cm- 3和 0 .2× 10 1 5cm- 3;最大衍射效率分别为 85 %和 72 % ;Ce∶LiNbO3和Ce∶Mn∶LiNbO3晶体的二波耦合响应时间分别为 3min和 3.5min。与Ce∶LiNbO3晶体相比 ,Ce∶Mn∶LiNbO3是性能更为优良的光折变晶体     

Ce0.8Nd0.2-xPrxO1.9固溶体的Raman光谱与阻抗谱

用溶胶-凝胶法合成了氧化铈稀土双掺杂Ce0.8Nd0.2-xPrxO1.9(x=0,0.10,0.15)固溶体。用X射线衍射(X-ray diffraction,XRD),Raman光谱和交流阻抗谱研究了固溶体的结构和导电性。XRD结果表明:经800℃焙烧所有的样品都形成了单相立方萤石结构,平均晶粒尺寸为22～32nm。X射线光电子能谱结果表明:样品中镨离子以混合价态(Pr3+和Pr4+)存在。Raman谱结果表明:Ce0.8Nd0.2-xPrxO1.9具有氧缺位的立方萤石结构,Pr离子的掺杂有利于氧缺位增加。阻抗谱表明:稀土双掺杂Ce0.8Nd0.2-xPrxO1.9(x=0.10,0.15)的电导率高于稀土单掺样品Ce0.8Nd0.2O1.9的,Ce0.8Nd0.05Pr0.15O1.9的电导率最大,在600℃时的电导率为2.63×10-2S/cm,导电活化能Ea=0.40eV(600～800℃),Ea=0.62eV(400～600℃),与Ce0.8Nd0.05Pr0.15O1.9材料内部更多的氧离子缺位和小极化子电子导电相关。     

Upconversion Luminescence and Mechanism of Cerium Doped YVO4 Crystals

在 YVO4晶体中分别掺入摩尔分数为 2%的 Ce2（CO3）3和 CeO2,在中频感应加热炉中采用提拉法生长了掺 Ce 的 Ce：YVO4晶体。用 X 射线衍射测试了这两种晶体的物相,发现两种样品都主要以 YVO4相存在。X 射线光电子能谱测试表明,在两种样品中铈离子都是以＋3、＋4 混合价态的形式出现的。光谱测试表明,两种样品的光谱特性非常相似,同时发现,两种方式掺杂的 Ce：YVO4晶体在 620 nm 的光激发下,均可发出以 450 nm 为中心的蓝色宽带荧光。分析认为,在 Ce：YVO4晶体中由 620nm 引发的上转换发光的激发过程,不可能直接起源于 Ce3＋的基态2F5/2,它起源于由特殊的“Ce–O”构型形成的电荷迁移态的基态。     

掺铁近化学计量比铌酸锂晶体的生长及其光学性能研究

在LiNbO3(LN)中掺进0．01％Fe3O3(质量分数)和10．9％K2O(摩尔分数)助熔剂，用顶部籽晶(TSSG)法生长近化学计量比掺铁铌酸锂(SLN：Fe)，以及采用Czochralski法生长同成分掺铁铌酸锂(CLN：Fe)。测试了晶体的晶格常数、吸收光谱和红外光谱。Li^ 取代反位铌(NbLi^4 )和占据锂空位，使SLN：Fe晶体的晶格常数变小。SLN：Fe晶体的吸收边相对于CLN：Fe晶体发生了紫移。SLN：Fe晶体的OH吸收峰移到3466cm^—1。利用二波耦合光路测试了晶体的指数增益系数和响应时间，计算了有效裁流子浓度。测试结果表明：SLN：Fe晶体的指数增益系数达到28cm^—1，而CLN：Fe晶体的指数增益系数为18cm^—1；SLN：Fe晶体的响应速度比CLN：Fe晶体提高了1个数量级。     

10%CeO2-ZrO2 Raman散射与t相晶格振动

为了从晶格原子振动方面进一步弄清ZrO2的t→m相变本质，测定了10％CeO2(in mole)-ZrO2(简写为10Ce)的Raman光谱。从室温到液氮温度（77K）的Raman光谱表明，降温过程中大约在153K发生了t→m相变。相变过程中，某些Raman谱峰的波数（频率）和半高宽发生了跃为：640cm^-1B1g模向低波数移动，320cm^-1B1g模和460cm^-1Eg模向高波数移动；640cm^-1B1g和320cm^-1B1g峰的半高宽亦有明显变化。实验结果表明：体现原子位移的某些Raman活性模波数跃变的实质是相变声子模的凝聚所致。另外，讨论了10Ce的t相晶格动力学，根据文献提供的Zr,O原子振动位移矢量绘制出了t相6个Raman活性模的晶格原子简正振动图像。     

Mg:Er:LiNbO3晶体的生长和抗光损伤性能

在1％(摩尔分数,下同)Er：LiNbO3中分别掺入2％,4％,6％的MgO,用提拉法生长Mg：Er：LiNbO3晶体。用X射线荧光光谱仪测试Mg：Er：LiNbO3晶体中Mg和Er的分凝系数。采用m线法研究Mg：Er：LiNbO3晶体波导基片光损伤阈值。结果表明：随着Mg^2 浓度的增加,Er^2 在LiNbO3中的分凝系数下降。6％Mg：1％Er：LiNbO3晶体波导基片光损伤阈值比1％Er：LiNbO3基片提高2个数量级以上。采用锂空位模型讨论Mg：Er：LiNbO3晶体光损伤阈值提高的机理。     

掺铈YVO_4晶体的上转换发光及其机理

在YVO4晶体中分别掺入摩尔分数为2%的Ce2(CO3)3和CeO2,在中频感应加热炉中采用提拉法生长了掺Ce的Ce:YVO4晶体。用X射线衍射测试了这两种晶体的物相,发现两种样品都主要以YVO4相存在。X射线光电子能谱测试表明,在两种样品中铈离子都是以+3、+4混合价态的形式出现的。光谱测试表明,两种样品的光谱特性非常相似,同时发现,两种方式掺杂的Ce:YVO4晶体在620 nm的光激发下,均可发出以450 nm为中心的蓝色宽带荧光。分析认为,在Ce:YVO4晶体中由620nm引发的上转换发光的激发过程,不可能直接起源于Ce3+的基态2F5/2,它起源于由特殊的"Ce-O"构型形成的电荷迁移态的基态。     

Co2+,Zn2+双掺杂铌酸锂晶体的坩埚下降法生长及其光谱特性

在LiNbO3中掺入0．1％（摩尔分数．下同）的CoO与3％,6％的ZnO,采用坩埚下降法技术生长了双掺杂的Co^2＋：Zn^2＋：LiNbO3晶体。用X射线衍射与差热分析表征了获得的晶体。测定了晶体不同部位在350～2500nm波段的吸收光谱。研究表明：Co离子位于LiNbO3晶体的崎变的氧八面体中,呈现＋2价,沿着生长方向Co^2＋在晶体中的浓度逐渐减少。ZnO的掺杂有效地抑制了Co^2＋离子在晶体中的掺入,使得Co^2＋在晶体中浓度的分布变得均匀。同时发现：ZnO的掺入使得上部晶体的熔点升高。从化学组分的角度解释了产生熔点变化的原因。观测到了750nm波长的荧光发射带。[编者按]     

无水氯化镧铈晶体的制备

用氯化铵氯化法制备出高纯无水氯化镧(铈)粉料,并以其为原料,用石英坩埚下降法生长出无色透明的掺3价铈的氯华镧(LaCl3:Ce)晶体.经测试,LaCl3:Ce样品的透过率达到80%,用137Cs发射源发射的γ射线激发LaCl3:Ce样品,得到的能量分辨率约为3.5%,晶体的光产额约为(6 510±50) photon-electrons/MeV,与碘化钠(铊)晶体(NaI:T1)相当.晶体的光学性能和闪烁性能表明:采用氯化铵氯化法制备的无水氯化镧(铈)粉料可直接用于晶体生长,而且生长出了高质量的LaCl:Ce晶体.     

Mg∶Er∶LiNbO_3晶体的生长和抗光损伤性能

在1%(摩尔分数,下同)Er∶LiNbO3中分别掺入2%,4%,6%的MgO,用提拉法生长Mg∶Er∶LiNbO3晶体。用X射线荧光光谱仪 测试Mg∶Er∶LiNbO3晶体中Mg和Er的分凝系数。采用m线法研究Mg∶Er∶LiNbO3晶体波导基片光损伤阈值。结果表明:随着Mg2+浓 度的增加,Er3+在LiNbO3中的分凝系数下降。6%Mg∶l%Er∶LiNbO3晶体波导基片光损伤阈值比l%Er∶LiNbO3基片提高2个数量级以 上。采用锂空位模型讨论Mg∶Er∶LiNbO3晶体光损伤阈值提高的机理。     

Growth and characterization of the Al-doped and Al–Sn co-doped ZnO nanostructures

In the present work, well-dispersed structures of spherical-like pure ZnO, Al doped ZnO (AZO) and Al, Sn co-doped ZnO (ATZO) nanocrystals were successfully synthesized by using zinc acetate dihydrate as the starting material and also the low temperature hydrothermal process without any additional surfactant or catalytic agent. The ZnO structures were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The XRD results revealed that ZnO powders have a hexagonal crystal structure and the TEM indicated that the nanoparticles self-aggregate. An X-ray photoelectron spectroscopy (XPS) study confirmed the substitution of Zn²⁺ by Sn and Al ions. Optical properties of the ZnO structures were investigated by Raman spectroscopy and room-temperature photoluminescence (PL) spectroscopy. The Raman spectroscopy results demonstrated that the doped ZnO nanoparticles had a higher crystalline quality than that of pure ZnO. Room-temperature PL spectra of these structures showed a strong UV emission peak and a relative weak green emission peak, and the UV peak of the doped ZnO nanoparticles was blue-shifted with respect to that of the undoped ZnO nanoparticles.     

X-Ray, Micro-Raman, Optical Absorption/Emission Studies of ErNbO4 Grown by Vapor Transport Equilibration

Vapor transport equilibration (VTE) treatments were performed on a Y-cut bulk Er (1.6 mol%)-doped congruent LiNbO₃ crystal and an X-cut pure congruent crystal, on one surface of which a 40 nm-thick film of erbium metal was coated before the VTE treatment. Scanning electron microscope, powder or single-crystal X-ray diffraction (XRD), polarized infrared absorption/emission of Er³⁺ as well as micro-Raman spectroscopy were used to study the two VTE crystals. The results are discussed in comparison with a corresponding as-grown bulk Er-doped crystal, calcined ErNbO₄ powder, and a locally Er-doped congruent LiNbO₃ crystal prepared by using the standard Er-diffusion technique. The experimental results show that the VTE treatment induces the formation of micrometer-sized ErNbO₄ precipitates with the crystallographic morphology of a flat polyhedron not only on the surfaces of both crystals but also in the bulk of the homogeneously Er-doped one. The optical absorption and emission studies show that the formation of the precipitates results in substantial spectral changes in both the 0.98 and 1.5 μm regions. The micro-Raman studies allow to resolve four additional Raman peaks around 800 cm⁻¹ in the E(TO) spectra of the two VTE crystals. These additional Raman peaks are associated with the characteristic vibrations with respect to the NbO₄³⁻ group. Characteristic XRD, optical absorption, and emission and Raman peaks for identifying the ErNbO₄ phase are proposed. Finally, the formation mechanism and light-scattering effect of the precipitates are discussed.     

Electrospun ferric ceria nanofibers blended with MWCNTs for high-performance electrochemical detection of uric acid

In this work, ferric ceria nanofibers (FC NFs) with different iron contents were successfully fabricated through electrospinning followed by calcination at 550 °C. The resultant FC NFs were blended with multi-walled carbon nanotubes (MWCNT@FC) and utilized to modify the glassy carbon electrode (GCE) for uric acid (UA) detection. The XRD patterns revealed that FCs NFs have cubic lattice structure. The Raman and X-ray photoelectron spectroscopy (XPS) were confirmed the presence of oxygen vacancies with Fe(II)/Fe(III) and Ce(III)/Ce(IV) chemical states of the surface ions. The surface morphology was investigated through scanning electron microscopy (SEM) and particle size analysis was performed using transmissions electron microscopy (TEM). The electrochemical properties of MWCNT@FC NFs were evaluated through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods under varied conditions. The results demonstrated the crucial effects of Ce/Fe molar ratio on the electrocatalytic performance due to the sufficient oxygen vacancies originating from the incorporation of Fe³⁺ ions into ceria (CeO₂). Furthermore, blending with 70 wt% MWCNT (MWCNT70@FC) gave rise to a significant improvement on the electrical conductivity. The MWCNT70@FC-2 modified GCE composite with Ce/Fe molar ratio of 1:1 displayed high performance towards UA detection at 6.0 pH.The detection limit of 0.3 μM was achived with wide linear range from 0.5 μM to 500 μM. The MWCNT70@FC-2 demonstartedadequate stability and reproducibility for urice acid detection. The high selectivity and accuracy was further established for prepared MWCNT@FC-2 composite sensor by detecting UA in real biological samples. The obtained results were precise and reproducible.     

Comment on an article by Gonzaga et al. J Am Ceram Soc. 2020;103:6280-6288

I argue that the authors’ interpretation of X-ray photoelectron spectroscopy (XPS) Ce3d spectra of their materials is untenable because it largely neglects the electronic structure of cerium ions and spin-orbit interaction of the Ce3d subshell. I conclude that at %Ce³⁺ values the authors derived from their Ce3d spectra offer an inaccurate account of the cerium chemistry of their materials.     

Helical nanocoiled and microcoiled carbon fibers as effective catalyst supports for electrooxidation of methanol

We have demonstrated a new synthesis of twist-shaped nanocoiled and herringbone-type double microcoiled carbon fibers via catalytic chemical vapor deposition of acetylene over NiCuMgAl-layered double hydroxides. The materials were characterized by power X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and N₂ adsorption-desorption experiments. For the first time, the use of electrodes modified with platinum particles supported on as-grown helical carbon fibers was studied for electrocatalytic oxidation of methanol. Especially, the electrode supported on herringbone-type double microcoiled carbon fiber showed much larger Pt active surface area than that supported on commercial carbon black. Furthermore, such electrocatalyst has exhibited about fourfold enhancement of activity and excellent anti-poisoning ability, which is believed to be attributed to the combined beneficial effects of novel microstructure and special composition of as-grown helical carbon fibers.     

N,Al共掺杂TiO_2纳米材料的制备及其可见光降解葛根素

采用固相反应法合成了Al掺杂TiO2(Al-TiO2)及N与Al共掺杂TiO2(N-Al-TiO2)纳米材料,采用XRD、SEM、UV-Vis DRS、XPS、Raman以及N2吸附-脱附等手段对材料进行了物相结构表征。同时考察了可见光辐照下催化剂对葛根素降解性能。N-Al-TiO2纳米材料的微观形貌为短棒形;氮以阴离子(N3-)形式取代氧进入TiO2晶格,形成N—Ti键,Al3+以同晶取代方式占据TiO2晶格中Ti的位置;其表面N、Al、Ti及O的原子百分比组成(%)分别为7.8、3.6、32.7和55.9;并对葛根素显示出很高的可见光降解活性,2 h对葛根素的降解率达92.7%。3种材料对葛根素的吸附容量与其对葛根素的可见光降解能力一致,依次为N-Al-TiO2>纯TiO2>Al-TiO。     

Optimization of Gallium concentration to improve the performance of ZnO nanopowders for nanophotonic applications

This study reports the effects of gallium concentration on the properties of doped zinc oxide nanopowders. Both pure and gallium doped zinc oxide (GZO) nanoparticles were prepared via a simple and effective sol-gel method. The structural, morphological and optical properties of synthesized GZO nanopowders were investigated using different characterization methods such as X-ray diffraction, Raman, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, UV–Vis diffuse reflectance spectroscopy, Transmission electron microscopy, Photoluminescence spectroscopy, X-ray and ion-beam-induced luminescence (IBIL) measurements. Firstly, in the presence of Ga ions in the host the purity of synthesized sample was evaluated by X-ray diffraction analysis. X-ray photoelectron spectroscopy confirmed the presence of bonding states of Zn, O, and Ga on the surface of powders. Raman spectroscopy analysis showed that the increase of Ga content upper than 1 at.% leads to an increase in the number of defects in the ZnO lattice. Field emission scanning electron microscopy (FESEM) confirmed that the uniform integration of spherical and hexagonal rod shape particles can be found in the doped samples. According to FESEM images, the particle size of prepared nanopowders increased from 101 to 200 nm by increasing in the Ga doping concentration. The photoluminescence, X-ray and ion beam induced luminescence results of the pure and doped ZnO powders revealed novel blue-green emission band from 400 up to 550 nm at room temperature. Optical and structural studies confirmed the optimized Ga concentration is 1 at.%.     

Defect induced magnetic transition in Co doped CeO2 sputtered thin films

Cobalt-doped cerium dioxide thin films exhibit room temperature ferromagnetism due to high oxygen mobility in doped CeO₂ lattice. CeO₂ is an excellent doping matrix as there is a possibility of it losing oxygen while retaining its structure. This leads to increased oxygen mobility within the fluorite CeO₂ lattice, leading to formation of Ce³⁺ and Ce⁴⁺ species. Magnetic ceria materials are important in several applications from magnetic data storage devices to magnetically recoverable catalysts. In this paper, the room temperature ferromagnetism of rf sputtered Co doped CeO₂ thin films is reported whereas undoped CeO₂ thin films exhibit paramagnetic behavior. The ferromagnetic properties of the Co doped films were explained based on oxygen vacancies created by Co ions in Ce sites. This is further supported by X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman. Change in surface morphology due to Co doping of the samples were analyzed using atomic force microscopy (AFM).     

SDS对甲烷水合物生成动力学和微观结构的影响

表面活性剂是促进水合物生成的有效手段之一。在高压反应釜中研究了十二烷基硫酸钠（SDS）对水合物生成过程的动力学影响,利用XRD和拉曼光谱探究了SDS存在条件下水合物的微观结构。宏观结果表明SDS缩短了诱导时间,加快了水合物生长速率。微观结果表明SDS没有影响sI型水合物的晶型结构,晶面间距与理想sI型水合物及纯水甲烷对比误差在千分之几。水合物中甲烷在大笼小笼中的拉曼位移分别为2904和2915 cm^-1,SDS没有改变大笼小笼结构。大笼绝对占有率（q_L）接近饱和时,SDS可以进一步提高小笼绝对占有率（q_S）,从微观角度证明了SDS可以减少水合数,提高储气率。     

Wet-Chemical Synthesis and Electrochemical Properties of Ce-Doped FeVO4 for Use as New Anode Material in Li-ion Batteries

Ce-doped FeVO₄ nanocomposites were successfully synthesized using reverse micro-emulsion route. Thermal and microstructural characteristics were comprehensively investigated by simultaneous thermal analysis, X-ray diffraction (XRD), scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and laser particle size analyzer. Moreover, as the anode material of lithium-ion batteries, the electrochemical properties were studied by galvanostatic charge and discharge tests and electrochemical impedance spectroscopy. The thermal analysis illustrated that the triclinic crystal structure of FeVO₄ nanoparticles is formed at about 520 °C, which is confirmed by XRD and FT-IR results. Furthermore, the microstructural analyses revealed more regular particles and high specific surface area for wet-chemical derived FeVO₄:Ce, which decreases the diffusion pathway of the lithium ions during the insertion/extraction process. The electrochemical measurements indicated that the electrode cycling performance and rate retention ability of Ce-doped FeVO₄ are better than those of pure FeVO₄ due to the expansion of the crystal lattice, which provided more lattice space for lithium intercalation and de-intercalation. Consequently, the as-prepared Ce-doped FeVO₄ with relatively high specific and reversible capacity, thermal stability and satisfactory cycling performance is a promising candidate for use as a lithium batteries anode material.