Electrical and Thermo-Physical Properties of Ni-Alloy Reinforced Bi-2223 Conductors

The improved mechanical properties of the Ni-alloy reinforced Bi2-xPbxSr2Ca2Cu3O10-x(Bi-2223) - released on 2016 by the Sumitomo Electric Industries, Osaka, Japan , (HT-NX type) - renewed the interest on this material for high-field applications. Whether Bi-2223 can be preferred to other high-temperature superconductors for very-high-field magnets depends also on the solutions found to protect the coil in the case of quenches. A comprehensive study of the quench propagation requires information about the temperature and field dependence of the critical current (I_C) , the thermal conductivity ( κ ) of the conductor, and the electrical resistivity of the normal matrix ( ρ norm ). Most of these data are unavailable in the literature for the HT-NX tape. This paper intends to fill this gap, reporting the results of an extensive measurement campaign of its electrical and thermo-physical properties. We have found that I_C decreases linearly with T in the investigated range of fields 1–19 T. The well-known magnetic hysteresis of I_C(B) has been examined in detail. We have observed that the value of I_C at a given field varies upon repeated I–V measurements, with a consequent reduction of the hysteresis amplitude. The longitudinal κ has been investigated in magnetic fields up to 19 T. ρ_norm has been measured between 4.2 K and 300 K and a residual resistivity ratio of ∼40 has been found. The experimental study of the I_C(T,B) surface, of the thermal conduction properties κ (T,B), and of the matrix electrical resistivity ρ_norm provides fundamental elements for a quench propagation study, which is critical in view of high-field applications of this conductor.