ELECTRICAL-PROPERTIES AND CORROSION OF BI-2223 COATINGS ON SILVER WIRES DIRECTLY SYNTHESIZED FROM A BI-2223 PRECURSOR OR FROM A BI-2223 BI-2212 MIXTURE/

Superconducting wires are prepared by coating of a silver substrate, b y sintering of a slurry deposited onto the metal core and containing a grinded (Pb doped) Bi-2223 ceramic, a grinded Bi-2223/Bi-2212 mixed c eramic or a grinded mixture of the Bi-2223 precursors, and of 20% PbO in excess. The resistance-versus-temperature R(T) curves obtained for a 6 days sintering at 835 degrees C presented only one drop, with Tc0 = 108K (107K when the slurry is a mixture of the Bi-2223 precursors). When the coating is obtained from a grinded Bi-2223/Bi-2212 mixed cera mic the R(T) curves are better (higher Te and narrower Delta Tc) than the RO curves obtained with the ceramic used for preparing the wires, for which Tc0 = 34K. The role of PbO in excess is discussed.These coat ings hold rather well against corrosion by waper vapor at 90 degrees C and the Bi-2223 phase is less corroded than the Bi-2212 phase.