RELATIONSHIPS BETWEEN DISLOCATIONS, 2ND-PHASE, AND PINNING IN Y-BA-CU-O

The pinning effects and the critical current density predicted to occu r in bulk YBa2Cu3O from second phase particles and from dislocations a re examined. It is shown that core or strain pinning by dislocations p rovides the best explanation of pinning forces, and that strain pinnin g by dislocations or particle pinning of individual (but not multiple) flux lines best fit the pinning energy. An experiment in which critic al current is increased when particles are coarsened by long molten ho lding times during melt processing is correlated with increased disloc ation density, despite a drop in volume fraction and increase in size of the added normal state particles. The combined aspects of these sug gest that strain induced pinning from dislocations may be the dominant mechanism in high critical current bulk materials.