Contact characteristics for bulk superconductors

We have studied the contact characteristics of two resin-impregnated bulk superconductors in mechanical contact. In the previous work, it was confirmed that a switching phenomenon between high and low resistance range took place at a threshold current or a transfer current value in the V-I curves of YBCO contact. In this paper we found that the transfer current exceeded 30 A and the contact resistance were decreased to 40 μΩ at 77 K in the mechanical contact when the sample surfaces were carefully polished. Moreover we succeed in decreasing the contact resistance to 6 μΩ with depositing the metal on the contact surface. The present results suggest that a pair of superconducting blocks might be applicable to the mechanical persistent current switch for superconducting magnetic energy storage and other superconducting systems running in a persistent current mode.