Relationships between dislocations, second phases, and pinning in Y-Ba-Cu-O

Abstract

The pinning effects and the critical current density predicted to occur in bulk YBa₂Cu₃O₇ from second phase particles and from dislocations are examined. It is shown that core or strain pinning by dislocations provides the best explanation of pinning forces, and that strain pinning by dislocations or particle pinning of individual (but not multiple) flux lines best fit the pinning energy. An experiment in which critical current is increased when particles are coarsened by long molten holding times during melt processing is correlated with increased dislocation density, despite a drop in volume fraction and increase in size of the added normal state particles. The combined aspects of these suggest that strain induced pinning from dislocations may be the dominant mechanism in high critical current bulk materials.