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Microstructure and critical current density in Bi(2223) superconductors prepared by solid-state electrolysis method

固态电解法制备Bi(2223)超导体的微观结构和临界电流密度

基本信息

批准号：
04650265
负责人：
OOTA Akio
金额：
$ 1.28万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Solid-state electrolysis method (SSEM) is effective particularly for purification of transition-metals with high melting points, where a DC current is passed through the sample during heat treatments at temperatures just below the melting point and impurity ions with positive or negative charges are moved away from the main part of the sample to the electrodes by the DC electric field. We applied this method for producing high critical currents I_c in high-T_c Bi(2223) superconductors.The co-precipitation powder was used as the starting material for sample preparation. It was packed with Ag coaxial cylindrical tubes consisting of the pipe and rod. The composite was swaged into 2.5 mm in diameter and sintered at 830 ﾟC in air for 100h and re-swaged into 2.2 mm in diameter. After Ag leads were attached to the pipe as electrodes, the sample was sintered again at 820-840ﾟC in air for 150h. During second sintering, we supplied DC current (5-15A) through ceramics part for 10-30h at the last stage of this sintering. The microstructure and critical current I_c of the samples were investigated.We prepared a large number of the samples with SSEM, and investigated the relation between the microstructures and the I_c values. There is no difference in microstructural factors between the samples with and without SSEM.However, the I_c histogram for the sample number shows that the sample with SSEM exhibits a peak around I_c=15-20A, while the sample without SSEM shows a monotonic decrease with I_c. This fact shows that the SSEM is effective for reproducing high I_c values well above 10 A in the Bi(2223) superconducting wires.

固态电解法(SSEM)对于高熔点过渡金属的提纯特别有效，在低于熔点的温度下进行热处理时，直流电流通过样品，带有正负电荷的杂质离子在直流电场的作用下从样品的主体部分移到电极上。我们将这种方法应用于高T_c超导体中产生高临界电流I_c的实验。它由管子和棒组成的银同轴圆柱管填充。该复合材料被锻造成直径2.5 mm，在830ﾟC的空气中烧结100h，然后再锻造成直径2.2 mm。将银导线作为电极连接到管子上后，在820-840ﾟC的空气中再次烧结150h。在二次烧结过程中，在此烧结的最后阶段，通过陶瓷部分提供直流电流(5-15A)，持续10-30h。研究了样品的微观结构和临界电流Ic，并用SSEM方法制备了大量样品，研究了样品的微观结构与临界电流Ic的关系。但样品数的I_c直方图显示，添加SSEM的样品在I_c=15-20A附近出现一个峰值，而未加SSEM的样品随着I_c的增加而单调下降。这一事实表明，SSEM能有效地再现远高于10A的高I_c值。