E. Preisler et al., ELECTRICAL CONTACTS ON BISMUTH-BASED BULK HIGH-TEMPERATURE SUPERCONDUCTORS IN HIGH-CURRENT APPLICATIONS, Superconductor science and technology, 7(6), 1994, pp. 389-396
High-current applications of high-temperature superconductor form part
s (e.g. plates, rods, tubes) need connections to conventional (copper)
current leads of resistivities below 10 muOMEGA cm2. Bismuth-based DS
CCO 2212 parts can be contacted by two different methods: (i) the conv
entional covering of the surface with gold or silver by sputtering or
by vapour deposition, which always needs a post-deposition thermal tre
atment, and (ii) applying silver sheet to the superconductor part duri
ng its fabrication by a melt casting process. In both cases resistivit
ies of 1-3 muOMEGA cm2 at 77 K could be achieved. Experiments and theo
retical considerations to localize the partial resistances within the
connection demonstrate that the interfacial resistivity of melt proces
sed contacts, as well as sputtered or vapour deposited contacts after
heat treatment, are lower by about one order of magnitude than the res
istivity of the total connection.