Microstructure, irreversibility line and flux dynamics in plastically deformed directionally solidified YBa₂Cu₃O₇

The microstructure and superconducting properties of directionally solidified YBa2Cu3O7/Y2BaCuO5 composites made to creep at 930°C, have been investigated using transmission electron microscopy, and dc and ac magnetic measurements. It is found that the plastic deformation of high critical current samples induces a shift of the irreversibility line toward lower fields and temperatures as a result of a decrease of the activation energy for flux motion. Such a superconducting behaviour is directly correlated with the observed microstructure, which is dominated by microcracks and large stacking faults that decrease the vortex correlation along the c axis.