Identification of grain boundary effects in current-voltage curves of polycrystalline high-T-c superconductors

Dissipation and critical current densities in high-T-c superconductors can depend on both intragranular flux creep and intergranular weak links. Separating these effects in polycrystals can be a formidable task. We present current-voltage data which can in some cases identify weak-link behavior, and verify it by using ion irradiation to greatly diminish the contribution from flux creep. We conclude that the occurrence of significant weak links in series with so-called strongly-coupled current paths may be more common than previously deduced.