Field dependence of critical currents in polycrystalline Bi-Pb-Sr-Ca-Cu-O superconductors

The field dependence of Jc in partial‐melt‐processed Bi1.6Pb0.3Sb0.1Sr2Ca2Cu3Ox has been investigated. The samples have a dense, polycrystalline microstructure of the (2223) phase with no significant crystallographic texture, and exhibit Tc(χ)∼105 K and transport Jc(H=0)∼104 A/cm2 at 4.2 K. In high magnetic fields (e.g., H=5 T), the transport Jc is somewhat reduced but is still of substantial value. While the high‐angle grain boundaries in the present, partial‐melt‐processed samples are by no means weakly coupled, the field dependence of the critical current density [Jc(0)/Jc(5 T)∼10] is somewhat stronger than in c‐axis textured samples [Jc(0)/Jc(5 T)∼3]. The grain boundaries in the present polycrystalline samples may thus be viewed, on the average, as ‘‘mild’’ weak links. These results clearly indicate the necessity for grain texturing if the full Jc capability of the BSCCO‐type superconductors is to be exploited.