Low Resistivity Contacts to Bulk High T sub c Superconductors.

Convenient methods for obtaining extremely-low-resistivity contacts to bulk high T sub c superconductors (rho sub c in the range of ~10 sup (-12) OMEGA-cm sup 2) are described. Three different configurations of silver contact metal in Y-Ba-Cu- O have been employed, i.e., embedded Ag wire, embedded Ag particles, and selectivity patterned Ag-clad on superconductor wire. In all three cases, the low-resistivity, metallic contacts are formed in-situ during the sintering or melt-processing of the superconductor, thus eliminating the need for separate steps of contact preparation such as vacuum deposition of contact metal and additional heat treatment. The distribution and morphology of the silver contacts will be discussed. The measured contact resistivities in the present work are the lowest reported for the high T sub c superconductors, and these methods may serve as a useful basis for important technologies needed for bulk superconductor applications.