Weak links in ceramic In-doped Bi-Pb-Sr-Ca-Cu-O

The effect of In doping on the superconductivity and weak links in Bi-Pb-Sr-Ca-Cu-O is investigated. The volume fraction of the 2223 phase decreases with In concentration. The dependence of the resistive transition curve rho (T) on the applied magnetic field is measured. The nature of the temperature derivative of the resistivity curves indicates the presence of a superconducting transition between grains, coupled by weak links with a distribution of critical temperatures, and the superconducting transition within grains. The intergranular transition is suppressed with the application of magnetic field in the samples with weak coupling strength between grains while the intragranular transition shifts slightly upwards. The width of the intragranular transition also increases with magnetic field due to dissipation.