Skarba Michal, Pekarčíková Marcela, Frolek Lubomír, Cuninková Eva, Necpal Martin
Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, Jána Bottu 2781/25, 917-24 Trnava, Slovakia.
Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841-04 Bratislava, Slovakia.
Materials (Basel). 2021 Feb 23;14(4):1052. doi: 10.3390/ma14041052.
We prepared overlap soldered joints of high-temperature superconducting tapes, using various materials and preparation conditions. In order to select the joints with optimal performance, we correlated their electrical properties (derived from current-voltage curves) with the microstructure of the respective joint cross-section by scanning electron microscopy. With the first group of joints, we focused on the effect of used materials on joint resistivity and critical current, and we found that the dominant role was played by the quality of the internal interfaces of the superconducting tape. Initial joint resistivities ranged in the first group from 41 to 341 nΩ·cm. The second group of joints underwent a series of thermal cyclings, upon which the initial resistivity range of 35-49 nΩ·cm broadened to 25-128 nΩ·cm. After the total of 135 thermal cycles, three out of four joints showed no signs of significant degradation. Within the limit of 100 thermal cycles, reliable soldered joints can be thus prepared, with normalized resistivity not exceeding 1.4 and with normalized critical current above the value of 0.85.
我们使用各种材料和制备条件制备了高温超导带材的重叠焊接接头。为了选择性能最佳的接头，我们通过扫描电子显微镜将其电学性能（由电流-电压曲线得出）与各个接头横截面的微观结构相关联。对于第一组接头，我们关注所用材料对接头电阻率和临界电流的影响，并且发现超导带材内部界面的质量起主导作用。第一组接头的初始电阻率范围为41至341nΩ·cm。第二组接头经历了一系列热循环，在此过程中，初始电阻率范围35 - 49nΩ·cm拓宽至25 - 128nΩ·cm。在总共135次热循环后，四个接头中有三个没有明显退化的迹象。因此，在100次热循环的限度内，可以制备出可靠的焊接接头，其归一化电阻率不超过1.4，归一化临界电流高于0.85的值。
