Effect of hot plastic deformation in oxygen on the critical currents of melt-textured Y-123/Y-211

The influence of an oxygen atmosphere present during high-temperature deformation of melt-textured Y-123/Y-211 on the current density is studied. To this purpose, Bridgman-grown Y-123/Y-211 is uniaxially deformed under compression at T = 950 degrees C with (epsilon) over dot = 2.10(-5) s(-1). Current densities are obtained from magnetization measurements applying the anisotropic Bean model for the field parallel/perpendicular to the crystallographic c-axis. For B parallel to c, the current densities of the deformed samples are lower than those of the non-deformed samples at low T and high B. For higher T and for B parallel to ab they are enhanced. TEM studies show a significant increase of dislocation density with cores in the ab plane introduced by the deformation. The suppression of j at low T is observed also after deformation in air, the enhancement at higher T is a new feature ascribed to the phase stabilizing effect of the oxygen atmosphere during deformation.