在工频外磁场下高温超导体的交流损耗

在工频外磁场条件下，研究了不同工艺的Bi-2223/Ag带和Cu位元素替代的YBa₂Cu_3-xSn_xO_y超导体的交流损耗.实验结果表明：在单芯Bi-2223/Ag带中，热处理时间、温度及超导芯厚度的增加都将增加Bi-2223相的含量，因而导致磁滞损耗增加.将单芯带细分成19芯Bi-2223/Ag带能减少磁滞损耗，但另一方面，超导芯间的耦合增加了银基体的涡流损耗，因此19芯带的损耗只比单芯带减少20%左右.在YBa关键词：

STUDY ON AC LOSSES OF HIGH Tc SUPERCONDUCTORS IN 50Hz APPLIED MAGNETIC FIELD

AC losses of Bi-2223/Ag tapes prepared by different processes and YBa₂Cu_3-xSn_xO_y bulk materials substituted partially by Sn for Cu have been investigated in a sinusoidal magnetic field H(t) with the frequency of 50 Hz at 77K. The experimental results showed that the appropriate decrease of temperature and time of the heat treatment can reduce AC losses in the monofilamentary tape.The reduction of thickness can also reduce AC losses.The subdivision of monofilamentary tape into multifilamentary tape will suppress the hysteresis loss.On the other hand, the coupling of interfilaments will increase the eddy current loss in Ag matrix.So the AC losses of the tape with 19 filaments are only about 20% less than the monofilamentary tape. The AC loss of Sn-added sample is lower than that of YBa₂Cu₃O_y.The content of Sn influences the dissipation characteristics of the YBa₂Cu_3-xSn_xO_y. The AC loss of YBa₂Cu_2.95Sn_0.05O_y is lower than that of YBa₂Cu_2.94Sn_0.06O_y.The addition of Sn has an important effect on the microstructure of the Y-system superconductor.The partial substitution of Sn for Cu can reduce the average size of Y₂BaCuO₅(211)particles and increase the boundaries between 211 and 123 phase. In addition,Sn can also lower the melting temperature of the Y-system superconductor.All of these lead to the increase of pinning-force and J_c hence the AC loss is decreased.