Grain orientation studies in YBCO superconductors by molten salt synthesis

The molten salt or the flux method is utilized in this study to fabricate a grainoriented YBa₂Cu₃O_7−x superconductor. The formation of YBa₂Cu₃O_7−x in the presence of molten salts of Na, K, Li belonging to chloride and iodide systems does not appear feasible due to the instability of the superconducting phase in these salt systems. Studies using the “green phase,” Y₂BaCuO₅, as seed crystals suggest a two-stage approach in the formation of YBa₂Cu₃O_7−x . The process uses Y₂BaCuO₅ formed by molten salt synthesis which has been observed to be stable in water and against most of the salts. The 211 crystals can be mixed with oxides and converted to 123. Analysis of X-ray data and SEM micrographs indicates a certain degree of grain orientation, which can be further enhanced by tape-casting or not-forging.     

Coupling Across an Intimate Ceprate-Manganite Interface

Electronic and magnetic coupling across the interface between a ferromagnetic La_2-xBa_xMnO₄ (“ colossal magnetoresistance” CMR) layer and a La_1.85Ba_0.15CuO₄ (high-temperature superconductor) layer are studied in a self-consistent virtual crystal approximation using the local spin density functional approach. The manganite material dopes the first cuprate layer, with holes ifx = 2/3 and with electrons if x = 0. Forx near the CMR regime the ferromagnetic manganite slab should be half-metallic. Such multilayer systems may be useful as magnetic field-controlled current switches, or as a relatively high-temperature superconducting material with small critical field.     

高温超导YBa2Cu3O7薄膜的颗粒,杂相生长机制研究

ＹＢａ２Ｃｕ３Ｏ７（ＹＢＣＯ）高温超导薄膜是重要的超导电子器件应用的材料，它们的质量对器件的运行性能至关重要。薄膜表面的颗粒使表面微波性能变坏，但有些生长在ＹＢＣＯ薄膜基体内部的小颗粒，会使薄膜的临界电流密度升高。     

Effects of precursor solution concentration on the properties and morphology of YBCO films deposited by TFA-MOD method

1 IntroductionMetal organic deposition using trifluoroacetates(TFA-MOD) process has been extensively investi-gated for the fabrication of YBa2Cu3O7-x(YBCO)films [1-3]. Compared with popular physical vapordeposition, TFA-MOD process has many advantages[4-5…     

各向异性衬底上的高温超导(HTS)微带天线

分析了各向异性衬底上的高温超导微带天线特性.选取两种典型的高温超导各向异性介质--GaNdAlO3和SrLaAlO4作为高温超导微带天线的衬底,采用各向异性媒质中的谱域矩量法,对微带天线的输入阻抗和辐射效率进行了计算.计算和分析结果表明,高温超导衬底的各向异性特性会影响高温超导微带天线的性能,而且这种影响因衬底而异,同时,衬底特性随温度的变化也将影响天线的性能.     

Bi-2223/Ag超导多芯带材的内切轧制研究

研究了Bi 2 2 2 3 /Ag超导多芯带材在一种新的加工方式—内切轧制过程中性能和组织的变化规律 ,采用XRD和SEM等测试方法对带材结构和组织进行了分析 ,并结合传统平辊轧制进行了对比。研究表明 ,相对于平辊轧制 ,内切轧制内辊和平辊轧制辊径相同时 ,采用内切轧制可以有效改善超导带材的组织结构 ,使得超导芯结构更加均匀 ,并增加超导芯的致密度 ,还可以有效改善带材内的银超界面状态 ,提高超导带材的电流传输性能。     

Surface resistance of superconducting leads at 6.5 GHz

The quality factor (Q value) of a cylindrical TEO11 mode lead cavity has been measured at 6.5 GHz in the temperature range 1.4–4.2 K. Lead was electroplated on a copper substrate. The temperature dependence of the surface resistance derived from the Q measurements has been compared with the semi-empirical formula of Pippard and the microscopic formula of Abrikosov, Gorkov and Khalatnikov (AGK). The plot fit is better with AGK. In this way, the normalized residual resistance (5.0 ± 0.2) × 10^?4 and the energy gap Δ(0) = (4.30 ± 0.05)kT_c was obtained.     

零电阻温度高于127KT1－2223超导体制备

本文采用初始成分为Ｔｌ＿１．８Ｃａ＿２．６Ｂａ＿２．０Ｃｕ＿３．０Ｏ＿ｙ，研究了一步合成和二步合成的短时间高温烧结及真空封闭较低温长时间热处理的Ｔｌ－２２２３制备工艺。用上述２种工艺均合成出单相性（２２２３）好的样品，其超导转变的起始温度Ｔｃ＿（ｏｎｓｅｔ）、零电阻温度Ｔｃｏ以及转变宽度△Ｔｃ分别为：一步合成样品Ｔｃ＿（ｏｎｓｅｔ）＝１３５Ｋ，Ｔｃｏ＝１２７．５Ｋ，△Ｔｃ＝５．０Ｋ，二步合成样品Ｔｃ＿（ｏｎｓｅｔ）＝１４０Ｋ，Ｔｃ。＝１２８．７Ｋ，△Ｔｃ＝７．５Ｋ。从制备工艺方面对提高Ｔｌ－２２２３的Ｔｃ进行了讨论     

高场超导磁体研究进展及其应用

高磁场对科学技术的发展具有极其重要的作用,它孕育着许多重大的科学发现和新技术的产生。超高磁场的产生和应用研究对极端条件科学设施、生物医学工程、国防特种装备、高精度的科学仪器以及农业应用都具有重要的意义。目前世界上许多研究机构和实验室开展了基于高温超导带材绕制高场直流超导磁体的项目。本文以高场超导磁体领域几个主要的研究机构为对象,主要介绍其在全超导高场磁体方面进行的研究工作,包括设计方案、技术特点和最新的研究进展,并对高场超导磁体的主要应用进行简要介绍。     

用于制备YBCO薄膜的光辅助MOCVD反应器内流动现象的数值研究

对一种制备YBCO薄膜的光辅助MOCVD反应器内的流动现象进行了三维数值模拟研究.在模拟计算中,分别改变基座与进口的相对角度(Φ)、反应器顶壁倾斜角度(Ψ),得出反应器中流场的相应变化.根据对模拟结果的分析,发现当基座平面与进气口轴线之间的夹角Φ=22.5°及反应器顶壁倾角ψ=30°时,基片表面气流速度大小合适,分布均...