Dependence of critical current (Ic) on weak links in metal/metal oxide added Bi-2212

The presence of weak links in high Tc superconductors is a major drawback in achieving high critical current densities. The present study deals with the effect of additives (Ag, Ag2O and BaBiO3) on the weak link behaviour of Bi-2212 in bulk form. It is observed that the addition of Ag up to 6 mole% improves the proximity between the grains and thereby enhances the current carrying capability even at temperatures very close to Tc. De Gennes and Clarke models have been invoked to establish that insulating additives (BaBiO3 and Ag2O) show a superconductor-insulator-superconductor (S-I-S) behaviour and thereby enhance the weak link network whereas metallic Ag shows a superconductor-normal metal-superconductor (S-N-S) behaviour and is therefore a potential candidate for large scale applications. Further support to this data is obtained from ac susceptibility studies carried out at various fields (0.1-4 Oe). (author)