Magnetic characterisation of large grain, bulk Y-Ba-Cu-O superconductor-soft ferromagnetic alloy hybrid structures

Large grain, bulk Y-Ba-Cu-O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell's algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the superconductor alone below this saturation level, and especially when the applied field is removed. The results of the study show further that the beneficial effects on the trapped field are enhanced when the ferromagnet covers the entire surface of the superconductor for different ferromagnetic components of various shapes and fixed volume. © 2014 Elsevier B.V. All rights reserved.

复杂无机离子晶体晶格能的研究

对于简单二元晶体（I-VII，II-VI，III-V族晶体），我们发现了它们的晶格能、德拜温度、等离子体能量、体变模量间的一些简单关系，分析发现了德拜模型的局限性，得到离子品体晶格能最小可能值为546kjmol-1，也发现碱金属卤化物的晶格能与格波的纵、横光学支的波数都呈线性关系，相同阳离子及相同阴离子的碱金属卤化物的LEELS、HEELS，ORS的谱峰能量值也与晶格能呈线性关系，说明这些量都与离子间的｛妾合强度有一定的关系。基于复杂靛．体化学键介电理论，并考虑到晶格能和键性的关系，我们发展了一种新的经验地计算晶．格能的方法，晶格能被视为是由各类键贡献的，对于每类键，其对晶格能的贡献被分为离子性和共价性两部分，复杂离子晶体被分解后得到的各类键可做相似处理。我们又基于Born理论模型，考虑到离子晶体中离子间主要作用是库仑作用及电子壳层的排斥作用，发展了另一种简单的计算晶格能的方法。对于很多静电键为主的功能材料（如巨磁阻材料、超导体等），用这两种方法计算的晶格能值与实验值及他人的计算结果相当接近，它们可以作为复杂离子晶体晶格能可信I均估算方法。我们还计算了YBCO体系的晶格能，并得到其与氧浓度的函数关系。

铜（III）及相关化合物的合成和性质的研究，稀土复合氟化物电性、氧敏和氢敏性质

本论文包括两部分内容。第一部分为“Cu(III)及相关化合物的合成和性质的研究”；第二部分为“稀土复合氟化物的电性、氧敏和氢敏性质”。第一部分的主要内容有：1.制备了Na_4H[Cu(H_2TeO_6)_2]·17H_2O和Na_4K[Cu(HIO_6)_2]·12H_2O的Cu(III)单晶配合物。2.在比较相应的Cu(II)化合物的条件下，详细地研究了这二个Cu(III)配合物的电子光谱和Cu2p光电子能谱，由于价态升高，场强参数增大，Cu(III)化合物的d-d跃迁相对于Cu(II)化合物d-d跃迁，发生“蓝移”。3.成功地实现了用O_3和电化学方法对强碱溶液中Cu(II)配合物的氧化，获得了二个新的Cu(III)固态配合物Ba_4K[Cu(H_2TeO_6)_2] (OH)_4·6H_2O和Ba_3K[Cu(HIO_6)_2] (KOH)_(0.5)(OH)_2·8H_2O利用化学分析、磁学性质、电子光谱和Cu2p XPS，对这二个化合物进行了表征。4.对BaCuO_(2.5)的合成、电学性质、磁学性质、Cu(III) ESR和Cu2p XPS进行了研究。5.以Na_4K[Cu(HIO_6)_2]·12H_2O和BaCuO_(2.5)为参照物，用电子光谱和Cu2p XPS，确认了YBa_2Cu_3O_(7-5)中的高价态的铜。6.考察了以Cu（III）化合物作为Cu部分原料所合成的YBCO系超导材料的电学性质。第二部分的主要内容有：1.测试了元件“BiF_3(Bi)/Ce_(0.95)Ca_(0.05)F_(2.95)/Pt”的氧敏、氢敏等性能。从室温到130 ℃，元件的氧敏机理为“双电子反应”，电动势（EMF）与氧分压遵循Nernst关系式。室温时，元件对空气中100Pa或1000Pa氢气的响应时间仅为15秒或短于5秒；氢分压在16Pa～1000Pa范围内，EMF与氢分压的对数呈线性关系，斜率为-116mV/decade, 敏感机理表现为“混合电极电势”。元件具有良好的氢敏性能，并有一定的选择性。2.合成并测试了La_(1-x)Pb_xF_(3-x)(X = 0.00 ～ 0.15)的电导率，La_(0.95)Pb_(0.05)F_(2.95)的电导率最高，比LaF_3高约一个数量级。以La_(0.95)Pb_(0.05)F_(2.95)为固体电解质材料，Pd或Pt为敏感电极，BiF_3(Bi)或PbF_2(Pb)为参比电极，制成了四个元件。其中，“BiF_3(Bi)/La_(0.95)Pb_(0.05)F_(2.95)/Pt”具有最好的氧敏、氢敏性能。从室温到150 ℃，元件的EMF与1gPo_2附合Nernst关系式。150 ℃时，元件对氧气的响应时间仅为80秒。室温下，元件对空气中100Pa或1000Pa氢气的响应时间仅为75秒或15秒，元件的电动势EMF与氢分压的关系可表示为“E=E_o-96lgP_(H2)(mV)”。元件对CO有较差的敏感性能，而对空气中甲烷、乙烷或乙炔（≤1000Pa）不具敏感性能。3.合成并测试了Ln_(1-x)Pb_xF_(3-x)(Ln=Ce、Pr、Nd和Gd、Dy、Ho、Yb)的电性。前四个系列为离子导体材料，后三个系列可能为P型半导体。随着Ln原子序数增大，LnF_3导电性能变差；La~(3+)、Ce~(3+)、Pr~(3+)、Nd~(3+)与Pb~(2+)离子半径差异较小，LnF_3和PbF_2可以形成固溶体；而Gd~(3+)、Dy~(3+)、Ho~(3+)、Yb~(3+)与Pb~(2+)离子半径差异较大，LnF_3和PbF_2难以形成固溶体。

OXYGEN ANALYSES IN HIGH-TC SUPERCONDUCTING FILMS BY MEV PROTON ELASTIC BACKSCATTERING

A technique for analysis of total oxygen contents in high-T(c) superconducting films is demonstrated. It uses elastic backscattering (EBS) of 1.5-2.5 MeV protons. By comparing the H EBS spectra from substrate materials, the absolute oxygen content in the films can be easily calculated. It is estimated that the analysis can be accurate to better than 5% for YBCO films with thicknesses from several hundred angstroms to several microns. Comparisons with RBS are given and advantages of this technique are shown.

Y-Ba-Gu-Nb-O的性质(英文)

在Y-Ba-Cu-Nb-O系统中,当Nb的含量较低时(x≤0.3),没有发现其晶格常数和超导转变温度Tc有明显变化,掺Nb能形成YBa_2NbO_6,BaNbO_3等;YBa_2NbO_6的新相比YBCO优先形成。当Nb含量x≥0.3时,少量的Nb进入123相的晶格,这种情况使b-轴变短,斜方变形加大,且Tc降低。

Y_(1—x)Ag_xBa_2Cu_3O_(7—y)的结构及超导电性

研究了Y_(1-x)Ag_xBa_2Cu_3O_(7-y)体系的结构。当x≤0.15时.该体系是固溶体.当0.150.5时,体系失去超导电性。在固溶体范围,Ag的置换改善了纯的YBCO脆性,增加了材料的机械强度,改善了颗粒弱连接.使体系的Jc从94.6A/cm~2提高到362A/cm~2。

A technique for mapping three-dimensional number densities of species in laser produced plumes

The potential of a diagnostic technique to provide quantitative three-dimensional (3D) density distributions of species in a low temperature laser-produced plume is shown. An expanded, short pulse, tunable dye laser is used to probe the plume at a set time during the expansion. Simultaneous recording of two-dimensional in-line absorbance maps and orthogonal recording of laser induced fluorescence permits the 3D density mapping by scanning the dye laser frequency. Preliminary data, supported by a simple model, is presented for the case of Ba II ions in a YBCO plume heated by a KrF laser. (C) 1996 American Institute of Physics.

THE ROLE OF GAS-PHASE OXIDATION AND COMBINATION DURING LASER DEPOSITION OF YBA2CU3O7-X IN AMBIENT OXYGEN

Spectroscopic absorption and emission measurements have been used to study laser deposition of YBCO films. They show that >95% of the monatomic Y and Ba initially ablated from the target undergo gas-phase chemical combination before film deposition. In contrast, considerable monatomic Cu persists into the deposition region. in this region, equilibrated gas temperatures are of the order of 2700 K. It is suggested that this high temperature facilitates film crystallization and epitaxial growth. The survival of monatomic Cu in the plume to the site of deposition is a manifestation of its endothermic reaction with O-2.

Temporal and Spatial Behavior of Electron Density and Temperature in a Laser-Produced Plasma from YBa2Cu3O7

Spectroscopic studies of laser -induced plasma from a high-temperature superconducting material, viz., YBa2Cu3O7 (YBCO), have been carried out. Electron temperature and electron density measurements were made from spectral data. The Stark broad ening of emission lines was used to determine the electron density, and the ratio of line in tensities was exploited for the determination of electron temperature. An initial electron temperature of 2.35 eV and electron density of 2.5 3 1017 cm2 3 were observed. The dependence on electron temperature and density on different experimental parameters such as distance from the target, delay time after the in itiation of the plasm a, and laser irradiance is also discussed in detail. Index Headings: Laser -plasma spectroscopy; Plasma diagnostics; Emission spectroscop y; YBa2Cu3O7.

Studies On Preparation And Characterization Of Hts Current Leads Using Multifilamentary Ag And Ag-Alloy Sheathed (Bi,Pb)-2223 Superconducting Tapes

The application vistas of superconductors have widened very much since the discovery of high TC superconductors (HTS) as many of the applications can be realised at 77 K rather than going down to 4.2 K, the liquid He temperature. One such application is the HTS current lead which is used to connect a superconducting system with a room temperature power source. Minimising heat leak to the cryogenic environment is the main advantage of introducing current leads into superconducting systems. The properties of HTSS likes zero resistance (avoiding joule heating) and very low thermal conductivity (minimized conductive heat transfer) make them ideal candidates to be used as current leads. There are two forms of HTS current leads. (i) bulk form (tube or rod) prepared either from YBCO or BSCCO and (ii) tape form prepared from Bi-2223 multifilamentary tapes. The tape form of current leads has many advantages with respect to the mechanical and thermal stability related criteria. Crucial information on various aspects of HTS current lead development are not available in the literature as those are kept proprietary by various companies around the world. The present work has been undertaken to tailor the properties of multifilamentary tapes for the current lead application and to optimise the processing parameters of the same for enhanced critical current density and field tolerance. Also it is the aim of the present investigation is to prepare prototype current leads engineered for operation in conduction cooled mode and test them for operational stability

Arranjo de antenas de microfita com substrato anisotrópico com patch supercondutor e aplicações em nanotecnologia

The main objective in this work is the analysis of resonance frequency microstrip structures with glass fiber and electromagnetic band gap (EBG/PBG) substrate and analysis of microstrip antennas with rectangular patch of superconductor of high critical temperature (HTS). In this work was used the superconductors YBCO (critical temperature of 90K), SnBaCaCuOy (critical temperature of 160K), and Sn5InCa2Ba4Cu10Oy (critical temperature of 212K) with results in Gigahertz and Terahertz. Was used microstrip antennas arrays planar and linear phase and linear phase planar with patch with superconductor. It presents a study of the major theories that explain superconductivity. In phase arrays were obtained the factors arrays for such configurations, and the criteria of phase and spacing between the elements compound in the array, which were examined in order to get a main lobe with high directivity and high gain. In the analysis we used the method of Transverse Transmission Line (TTL) used in domain of the Fourier Transform (FTD). The LTT is a full wave method, which obtains the electromagnetic field in terms of the components transverse of the structure. The addition of superconductive patch is made using the boundary condition resistive complex. Results are obtained resonance frequency as a function of the parameters of the antenna, radiation patterns of the E and H Planes, for the phase antenna arrays in linear and planar configurations, for different values of the phase and the spacing between elements

Heat-treatment effects on the magnetic response of superconducting mesoscopic samples

The use of chemical methods in the synthesis of high-quality and small-size polycrystalline samples has been increased in recent years. In this work, a chemical route based on an aqueous precursor solution of metals followed by the addition of a water-soluble polymer formed by ethylenediaminetetraacetic acid (EDTA) and ethylene glycol (EG) was tested to produce superconducting mesoscopic YBa(2)Cu(3)O(7-gamma) samples. Different conditions of heat treatments and the effects of argon and oxygen atmospheres during the calcination steps were traced using X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetic measurements. (C) 2008 Elsevier B. V. All rights reserved.

Oxygen dynamics and the effects of heat treatments in SBCO samples investigated by mechanical spectroscopy

The compound SmBa(2)Cu(3)O(7-delta) (SBCO)-obtained by substituting rare-earth Sm for Y in the well-known and most studied YBa(2)Cu(3)O(6+delta) (YBCO)-is potentially attractive to study in order to understand the superconductivity mechanism in physics and in electronic device applications. For SBCO, the possibility of variable stoichiometry and the high mobility of oxygen in CuO(x) planes give rise to a rich phase diagram. This study reports on the effect of heat treatments in an oxygen atmosphere on the anelastic properties of this oxide, in which relaxation processes were observed, attributed to oxygen atom jumps present in the Cu-O planes during the orthorhombic phase.

Analysis of the E-J Curve of HTS Tapes Under DC and AC Magnetic Fields at 77 K

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chelating agent effects in the synthesis of mesoscopic-size superconducting particles

Several routes and procedures have been used in these last years as an effort to achieve single-phase mesoscopic-size superconducting samples. In this paper, the effects of using citric acid (CA), tartaric acid (TA) and ethylenediaminetetraacetic acid (EDTA) as chelating agents and ethylene-glycol (EG) as polyhydroxy alcohol were studied in order to establish conditions to avoid the occurrence of BaCO(3) undesirable secondary phase in YBa(2)Cu(3)O(7-delta) (YBCO). Thermal evolution of intermediate compounds formed during the calcinations process by the use of different chelating agents was traced using thermogravimetric and spectroscopic methods. The obtained results indicated that the polymer breakdown of samples prepared using EDTA occurs at higher temperatures than others chelating agents and also reduces the occurrence of BaCO(3) secondary phase as studied by X-ray diffraction measurements. Furthermore, the magnetic response of the mesoscopic-size YBCO specimens obtained was verified showing that samples present different superconducting response.