Contact resistance characteristics of high temperature superconducting bulk-II

We have studied the contact characteristics of two resin-impregnated Y-Ba-Cu-O (a composite of YBa₂Cu₃O₃ and Y₂BaCuO₅+10wt%Ag₂O) bulk superconductors in mechanical contact. In the previous work, fundamental characteristics of mechanical contact between twoYBCO bulks were studied. A switching phenomenon between high and low resistance range could be observed at a threshold current or a transfer current value in the V-I curves. In this paper, we found that the transfer current exceeded 30 A and the contact resistance decreased to 40 μΩ at 77 K for the mechanical contact when the sample surfaces were carefully polished. Moreover we succeeded in decreasing the contact resistance to 6 μΩ by depositing metal on the contact surface. The present results suggest that a pair of YBCO blocks might be applicable to the mechanical persistent current switch for superconducting magnetic energy storage and other superconducting systems that are run in a persistent current mode.