Current distribution and microstructure studies of isolated filaments extracted from Ag-sheathed Bi(2223) tapes
Current distribution and microstructure studies of isolated filaments extracted from Ag-sheathed Bi(2223) tapes
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Ag护套Bi(2223)带中提取的孤立细丝的电流分布和微观结构研究
DOI：
10.1088/0953-2048/13/10/312
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发表时间：
2000
影响因子：
3.6
通讯作者：
G. Grasso
中科院分区：
文献类型：
--
作者：
G. Strano;A. Siri;G. Grasso
通过管内氧化物粉末技术制备的银包套（Bi，Pb）₂Sr₂Ca₂Cu₃O₁₀₊ₓ带材中提取出的所有细丝，已通过对银基体进行化学蚀刻而分离出来，并通过追踪它们在导体内部的位置进行了单独表征。对每根细丝都进行了不同类型的测量：通过超导量子干涉仪磁强计测量磁化磁滞回线和零场冷却直流磁化率；通过四探针法测量电阻率；通过X射线衍射分析相纯度和织构；通过扫描电子显微镜/能量色散X射线分析化学计量比。根据磁化磁滞回线计算出了每根细丝的临界电流密度\(j_{c}\)。在77K时发现，最里面的细丝的\(j_{c}\)为53kA/cm²，即比外层所有细丝的\(j_{c}\)（\(j_{c}\)在25到40kA/cm²之间）大得多。这些结果与在相同样品上观察到的室温电阻率变化是一致的。在某种程度上，观察到的电流分布可归因于细丝所经历的不同冷加工量。另一方面，我们发现中心细丝的平均化学计量比与初始前驱体粉末的化学计量比匹配良好，而在外层细丝中观察到Pb有持续的损失。外层细丝的氧含量也较低。
All the filaments extracted from an Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3O10+x tape, prepared by the oxide-powder-in-tube technique, have been isolated by chemical etching of the silver matrix, and individually characterized by keeping track of their position inside the conductor. Different types of measurements have been performed on each filament: magnetization hysteresis loops and zero-field cooled DC susceptibility by SQUID magnetometry; electrical resistivity by the four-probe method; phase purity and texture by x-ray diffraction analysis; and stoichiometry by scanning electron microscopy/energy dispersive x-ray analysis. The critical-current density jc of every filament has been calculated from the magnetization hysteresis loops. At 77 K it has been found that the innermost filament carries a jc of 53 kA cm-2, i.e. much larger than for all the filaments of the outer shell (with jc ranging between 25 and 40 kA cm-2). These results are consistent with the variation in room temperature electrical resistivity observed on the same samples. To some extent the observed current distribution can be imputed to the different amount of cold working experienced by the filaments. On the other hand, we have found that the average stoichiometry of the central filament matches well with that of the initial precursor powders, while in the filaments of the outer shell a consistent loss of Pb has been observed. The outer filaments also present a lower oxygen content.