Interface pinning in high T-c-high J(c) Nd1+xBa2-xCu3Oy directionally solidified in air

Single domain bars of NdBa2Cu3O7/Nd4Ba2Cu2O10 (Nd123/422) superconducting composites have been fabricated in air by using a directional solidification technique. T-c values of 96.5 K can be obtained after an Ar heat treatment and further oxygenation thus showing that reduced oxygen partial pressure during solidification is not a fundamental requirement to prepare high-T-c Nd123 bulk superconductors. The temperature dependence of the critical currents point to a limited efficiency of the Nd123/422 interfaces to pin vortices. High resolution electron microscopy observations clearly reveal smooth Nd123/422 interfaces thus suggesting that interface pinning may not be as relevant as compared to Y123/211 composites. (C) 1997 American Institute of Physics.