Electrical resistivity in Bi 2Sr 2CaCu 2O 8± δ compounds synthesized via melt-casting

Abstract

We performed detailed measurements of electrical resistivity ϱ versus temperature T in superconducting Bi 2Sr 2CaCu 2O 8± δ compounds prepared by melt-casting followed by recrystallization at higher temperatures under v conditions. Differential thermal analysis (DTA) suggests that the recrystallization process starts near 460°C, and that the superconducting phase starts developing near 780°C. The porosity of the annealed materials depends strongly on the annealing temperature, time, and heat-up rate. Typically a sharp drop in ϱ at the onset of superconductivity is followed at lower T by either a shoulder-like feature, a tail-like feature, or both. The ϱ versus T data, SEM, and porosity analysis suggest that weak links with narrow or broad distribution of sustaining critical current densities J c are responsible for the latter behaviors, respectively.