We measured the contact resistance of a silver block with convex curvature and silver, a melt-textured Y-Ba-Cu-O sample (YBCO), and a silver-deposited YBCO sample (dAg/YBCO) to clarify the main source of the resistance. The study was performed with the development of a persistent current switch in mind. The contact resistance was largest in the Ag/YBCO contact. It decreased by increasing the thickness of the deposited-Ag layer for the Ag/dAg/YBCO contact. However, the smallest resistance of the Ag/dAg/YBCO contact was even larger than that of the Ag/Ag contact. This is probably due to the fact that the Ag/dAg/YBCO contact has two interfaces. The present result suggests that the contact area is dominant in controlling the contact resistance. A simulation study of the contact area with a finite element method (FEM) also supported this idea.
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