拉伸应变对YBCO涂层导体传输特性的影响

本文通过实验研究了拉伸应变对YBCO涂层导体的临界电流(Ic)、n值和交流损耗的影响(零场,77K),实验结果表明,随着拉伸应变的增大,YBCO涂层导体Ic的变化分为三个阶段,开始缓慢上升,然后缓慢下降,最后快速下降,Ic的上升表明带材中存在残余压缩应变,Ic的衰减是由于应变导致弱连接区域的钉扎势与晶界间临界电流密度同时减小引起的;而n值随应变增加基本上没有变化,说明沿导体长度方向的Ic分布没有变化.由于临界电流密度沿样品宽度方向分布不均匀,实验所得的交流损耗结果与采用Norris模型计算所得的结果不一致,同时,当应变超过不可逆应变、电流接近Ic时,交流损耗快速增加.

EFFECT OF TENSILE STRAIN ON THE TRANSPORT CHARACTERISTICS OF YBCO COATED CONDUCTOR

In this paper, the effect of tensile strain on the transport characteristics of YBCO coated conductor has been investigated at Ic, n value and self field and 77K. It is observed that the Ic versus strain curve can be divided into three regions. The increase of Ic in the beginning can be attributed to the residual compressive stress and the degradation of Ic thereafter is the result of the decreases of both the pinning potentials in the weak-link area and inter-grain critical current density. Meanwhile n value showing little variation in the testing range indicates that the plastic deformation has little influence on the longitudinal Ic distribution. In AC case, the experimental result is not consistent with ellipse Norris model, which can be attributed to the non-homogeneous distribution of current along the conductor width direction. When the strain exceeds the irreversible limit and the current approaches Ic, AC loss increases remarkably.