Improvement of pinning in Bi2212-based materials by hot plastic deformation

Hot plastic deformation of bulk Bi2212 strongly improves pinning by introducing strong pinning centres accompanied by the formation of a high degree of texture. This is proved by an increase in critical current density and mean effective activation energy obtained from relaxation measurements, as well as from a large shift of the irreversibility line. The analysis shows that a simple interpretation of the U(J)-relation in terms of collective creep theory is not possible. Admixture of MgO particles gives similar, but less good results.