Stress- and field-dependence of critical current in Ba sub 2 YCu sub 3 O sub (7 - delta).

Superconductors in practical applications are subjected to large stresses such as caused by coil winding, thermal contraction, and the Lorentz force generated by magnetic field. In this paper, the stress and field dependence of the critical current density (J sub c) of the high-temperature superconductor Ba sub 2 YCu sub 3 O sub (7-delta) has been investigated. It has been found that the J sub c value is essentially independent of the applied stress, tensile or compressive, up to the level of fracture stress. This observation suggests that the grain boundary stress concentration is not likely to be one of the major causes of the "weak links" responsible for the relatively poor J sub c values in polycrystalline Ba sub 2 YCu sub 3 O sub (7-delta). The rapid deterioration of J sub c in applied magnetic field does not seem to be affected by the co-presence of applied stress.