Structural,Magnetic and Optical Properties of Rh2☎ Centres in NaCl Lattices: An Explanation

A method for exploring Jahn—Teller systems in the framework of Density Functional Theory is described in the present work. Using such a method the properties of the Rh^2? centre in NaCl with remote charge compensation are studied. The calculations support the existence of a strong Jahn—Teller effect and account reasonably for the main features of EPR and optical spectra. The onset of charge transfer excitations is calculated to be at about 3.7 eV a fact which concurs with available experimental data. The elongated geometry is found to be about 200cm^?1 more stable than the compressed one in agreement with experiments.     

Persistent Luminescence of Eu2☎ and Na☎ Doped Alkaline Earth Aluminates

The luminescence and afterglow properties of the Eu^2? and Na^? doped alkaline earth aluminales, stoichiometric and non-stoichiometric (M_x Al₂O₄:Eu^2?, Na^?; M = Ca or Sr, x = 0.97, 1.00 or 1.03, X_Na, = 0.02), were studied. Broad band luminescence and afterglow of the Eu^2? ion were observed in the blue (λ_max = 440nm) and green (λ_max = 520nm) region for the calcium and strontium aluminates, respectively. Both Na^? co-doping and strontium excess quenched the afterglow efficiently. The results supported the mechanism of the persistent luminescence where the cation vacancies act as traps. The results for the calcium aluminates were ambiguous, probably due to the slightly larger ionic radius of the Na^? with respect to that of Ca^2?. The sodium ions may not fit into the calcium sites and thus form (an) independent compound(s).     

Characterization of the electrical properties of Y2O3-doped CeO2-rich CeO2–ZrO2 solid solutions

Electrical properties of Y₂O₃-doped CeO₂-rich ZrO₂–CeO₂ system were characterized with a view point of its point-defect structural scheme. Theoretical calculation of partial electronic and ionic conductivity from total conductivity was done to investigate the combined homovalent and aliovalent doping effect on the overall electrolytic property. According to our study, combined homovalent and aliovalent doping can be one of the key solutions to overcome the fatal disadvantage of limited electrolytic stability of doped ceria system by which properly enhances the ionic conductivity and suppresses the electronic conductivity all at once. Feasibility and limitation of Y₂O₃-doped CeO₂-rich ZrO₂–CeO₂ system as a potential alternative electrolyte material for low or intermediate temperature SOFC were discussed.     

Explanation of Effect of Added Water on Dye-Sensitized Nanocrystalline TiO2 Solar Cell： Correlation between Performance and Carrier Relaxation Kinetics

Time-resolved mid-IR transient absorption spectroscopy is employed to explore the mechanism of improving the performance of dye-sensitized TiO2 solar cell （DSSC） when a certain amount of H2 0 is added into the electrolyte. The relaxation kinetics of dye-sensitized TiO2 nanocrystalline film and the corresponding DSSC performance are investigated under different conditions. It is found that the interracial charge recombination is retarded and electron injection efficiency is increased in the water vapour and in the electrolyte when D20 is added. The values of open-circuit photovoltage Voc and the short-circuit photocarrent Jsc of the cells are linearly correlated to the product of the two decay time constants. We also observed that Voc well correlates with electron injection efficiency. It provides a preliminary microscopic account for the function of the added water in improving the performance of DSSCs.     

EPR Study of Nd3☎ Ions in β-BaB2O4 Single Crystals

An Electron Paramagnetic Resonance (EPR) study of Nd^3? ions in single crystals of the low-temperature phase of barium borate (β-BaB₂O₄ or BBO) is presented. The EPR spectra show the existence of a minimum of three different Nd^3? centres. The g-matrices for three of the centres have been determined from the analysis of the angular dependencies of the spectrum in two planes of the crystal. This study allows us to conclude that neodymium is incorporated in the low-symmetry Ba^2? site. Possible reasons for the appearance of various Nd^3? centres are discussed.     

Spectroscopic and Structural Properties of Ca1-xSrxAl2O4:Eu2☎, RE3☎ Persistent Luminescence Materials

The preparation, structure and luminescence of the Ca_1-xSr_xAl₂O₄:Eu^2?, RE^3? system were studied. Monoclinic CaAl₂O₄ was the major phase when the strontium content x was from 0 to 0.6, but hexagonal SrAl₂O₄ was obtained when x was 0.8 and monoclinic SrAl₂O₄ when x was 1. Only slight Ca/Sr cation solid solubility was observed. The strontium ions dissolved better into the CaAl₂O₄ phase than vice versa. Two luminescence bands were observed for mixed compositions, peaking at 440 and 530 nm, corresponding to those of the monoclinic CaAl₂O₄:Eu^2? and hexagonal SrAl₂O₄:Eu^2? ones. The persistent luminescence was enhanced by the Ca/Sr replacement. This observation supports the mechanisms where the lattice defects act as traps.     

蓝宝石衬底上Gd2O3掺杂CeO2氧离子导体电解质薄膜的生长及电学性能

采用反应磁控溅射方法,在(0001)蓝宝石单晶衬底上,制备了纳米多晶Gd2O3掺杂CeO2(GDC)氧离子导体电解质薄膜,采用X射线衍射仪(XRD)、原子力显微镜(AFM)对薄膜物相、结构、粗糙度、表面形貌等生长特性进行了表征,利用交流阻抗谱仪测试了GDC薄膜不同温度下的电学性能;实验结果表明,GDC薄膜为面心立方结构,在所研究的衬底温度范围内,均呈强(111)织构生长;薄膜表面形貌随衬底温度发生阶段性变化:衬底温度由室温升高到300℃时,对应球形生长岛到棱形生长岛的转变,当完全为棱形岛生长时(300℃),生长岛尺寸显著增大;从400℃开始,则发生棱形生长岛到密集球形生长岛的转变,球形生长岛尺寸明显减小.生长形貌的转变反映着薄膜生长初期不同的成核机理,很可能与蓝宝石(13001)面的表面结构随温度变化有关;GDC多晶电解质薄膜的复平面交流阻抗谱主要源于晶界的贡献,根据Arrhenius图求得电导活化能Ea在1.2-1.5 ev范围内,接近于晶界电导的活化能值,并且随衬底温度升高Ea减小(Ea300 > Ea400> Ea600 );电导活化能以及晶粒尺寸不同,导致GDC薄膜电导率随测试温度的变化规律不同.     

Comparative Studies of Er3☎ Ions in LiNbO3 Waveguides Produced by Different Methods

We compare the optical properties of Er^3? in LiNbO₃ waveguides produced by different techniques and find by confocal luminescence microscopy characteristic differences in the excitation and emission transitions. Besides a small redistribution among the regular defect sites, essentially no direct Er^3?—Ti^4? interaction can be observed in Ti^4? diffused waveguides. However a significant shift in transition energies is found, which increases with Ti^4?concentration. Based on earlier results we associate this shift with a decrease in the intrinsic electric field. In addition to a similar shift, we find in Zn^2? diffused waveguides new defect types which suggest a change in direct environment. Finally, in annealed proton exchange waveguides we find no interaction effects at all.     

Photoluminescence Enhancement Effect of CeO2 in Rare Earth Composites MM′O3/CeO2 and MM′O3/CeO2: Pr3+ (M = Ca, Sr; M′ = Ti, Zr)

In the context, a modified sol-gel technology was afford to the synthesis of rare earth composite ceramic phosphors MM′O₃/CeO₂ and MM′O₃/CeO₂: Pr³⁺ (M = Ca, Sr; M′ = Ti, Zr) with multicomponent hybrid precursors were composed. The micromorphology, particle size and photoluminescence properties were studied with XRD, SEM and luminescent spectroscopy in detail. Both XRD and SEM indicated the particle sizes were in the submicrometer range of 100 ∼ 300 nm. The photoluminescence for these ceramic phosphors were studied in details with the different component of host (molecular ratio of Sr, Ca and Ti, Zr), presenting a broad spectral band in the visible blue-violet region with the maximum excitation peak at 449 nm and a wide emission range with a maximum peak at 619 nm, which was ascribed to be the characteristic transition of Pr³⁺ (¹D₂ → ³H₄). These phosphors can be expected for visible light conversion (blue → red) materials. Especially it can be found that the introduction of CeO₂ can enhance the luminescence intensity of MM′O₃ and MM′O₃: Pr³⁺.     

The Measurements of Photostimulated Luminescence in Alkali Doped BaFBr:Eu2☎ at Liquid Nitrogen Temperature

Considerable increase of the photostimulated luminescence (PSL) intensity and red shift of the excitation spectrum was obtained by alkali doping of BaFBr:Eu^2? crystals [1]. The band of the F_A(Br^?) centers about 0.1 eV shifted to low energy side against the “normal” F(Br^?) centers. The F_A(Br^?) centers are destroyed after heating to 330 K.     

Attenuation of Nuclear Orientation of 127In in Gd and the InGd Korringa Spin–Lattice Relaxation Time Constant

The nuclear spin–lattice relaxation of ¹²⁷In implanted into pure gadolinium metal has been measured using the method of integral attenuation of on-line nuclear orientation. The Korringa constant is determined to be C_K (¹²⁷InGd, B_pol = 0.5 T) = 0.133(18) sK. The result is compared with relaxation of In nuclei inFe.     

Gd2O3:Eu3+溶胶-凝胶薄膜发光特性研究

以无机稀土氧化物为原料制备了Gd2O3:Eu3 溶胶-凝胶薄膜,通过对不同Eu3 离子掺杂浓度、不同烧结温度薄膜发光强度的研究,得出Gd2O3薄膜中Eu3 离子的最佳掺杂浓度为10%、最佳热处理工艺为800℃下烧结2h;由薄膜和粉末激发谱的比较发现:薄膜中存在着比粉末更有效的能量传递,从而更有利于高能射线激发发光;首次观察到薄膜经过1000℃烧结2h后发光消失,并通过SEM和XRD的实验分析对这一现象进行了解释。     

Structural Transition of Gd2O3：Eu Induced by High Pressure

The structural transition of bulk and uano-size Gd2O3：Eu are studied by high pressure energy disperse x-ray diffraction （XRD） and high pressure photoluminescence. Our results show that in spite of different size of Gd2O3 particles, the cubic structure turns into a possible hexagonal one above 13.4 GPa. When the pressure is released, the sample reverses to the monoclinic structure. No cubic structure presents in the released samples. That is to say, the compression and relaxation of the sample leads to the cubic Gd2O3：Eu then turns into the monoclinic one.     

CeO2:Eu3+反蛋白石的制备与性质研究

以自组装法制备的面心立方结构的聚甲基丙烯酸甲酯(PMMA)蛋白石为模板,采用溶胶凝胶法制备二氧化铈(CeO2)掺杂铕离子(Eu3+)的反蛋白石结构光子晶体.利用XRD,SEM,UV-Vis等测量手段研究了光子禁带特性,样品在低温下的发光特性也被研究.结果表明CeO2:Eu3+反蛋白石的光子禁带是413nm,PMMA蛋白石的光子禁带是612nm,与理论计算结果十分吻合.且随着温度的降低,Eu3+离子所处晶体场的对称性下降.     

纳米Gd2 O3:Eu3+中Judd-Ofelt参数的实验确定

报道用Judd-Ofelt理论研究立方相纳米晶Gd2o3:Eu3+材料在77K下的光谱性质.以几乎不受周围晶场环境影响的5D0→7F1跃迁为参考,利用5D0→7F2和5D0→7F4跃迁,从实验上确定强度参数Ωλ(λ=2,4).发现纳米Gd2O3:Eu3+材料晶场强度参数Ωλ随纳米晶粒径的变化而改变,与体材料相比有显著的不同.随微晶粒径减小,发射能级5D0的寿命变短、量子效率降低.这是因为微晶粒径越小,量子限域效应越强,表体比越大,在无序体调制的表面上表面缺陷作用增强而引起的.对电荷(Eu3+-O2-)迁移态和多声子过程另外两种无辐射通道也进行讨论.     

Misfit Stress Relaxation in α-Ga2O3/α-Al2O3 Heterostructures via Formation of Misfit Dislocations

Physics of the Solid State - A theoretical model of misfit stress relaxation in film/substrate α-Ga2O3/α-Al2O3 heterostructures with allowance for lattice anisotropy of heterostructure...     

Point Spectrum and SULE for Time-Periodic Perturbations of Discrete 1D Schrödinger Operators with Electric Fields

We use the KAM technique to present a proof of pure point spectrum for the quasi-energy operator and a version of the SULE condition for suitable small time-periodic perturbations of discrete one-dimensional Schrödinger operators with uniform electric fields.     

Relaxation structure analysis of Li inserted γ-Fe2O3

γ-Fe₂O₃ has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe₂O₃, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe₂O₃ (x = 0.66, 1.1, 1.5 in terms of Li_XFe₂O₃), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe₂O₃ with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically.     

八面体结构纳米CeO2:Er^3+;的合成及发光性质

采用水热合成法制备了八面体结构纳米CeO2∶Er^3+,并研究了稀土Er^3+离子掺杂对CeO2纳米晶的结构以及发光特性的影响。所合成的CeO2纳米晶具有八面体结构,结晶完好,粒度均匀。XRD和拉曼光谱测试结果表明所制备的CeO2纳米晶为面心立方萤石结构,稀土Er^3+离子的掺杂在基质晶格中产生了氧空位缺陷,并产生了晶格畸变。在980 nm激光激发下产生了稀土Er^3+离子绿色(2H11/2,4S3/2→4I15/2)、红色(4F9/2→4I15/2)和近红外(4I11/2,4I13/2→4I15/2)发光。随着稀土Er^3+离子掺杂浓度的变化,样品的发光光谱在可见光和近红外光范围产生了不同的猝灭浓度,这是由于掺杂浓度变化对Er^3+-Er^3+之间的交叉驰豫过程产生了影响,Er^3+的能级布居变化引起了发光特性的改变。