Processing and grain boundary effects in Nd1-xBa2-x Cu3O7+d superconductors

Nd_1-xBa_2-xCu₃O_7+d samples have been prepared with sharp superconducting transitions, with careful attention given to the details of sample preparation. Two causes for broad samples have been observed. The first is sample inhomogeneity, which is more difficult to eliminate than in the YBa₂Cu₃ O₇ case, and the second appears to be associated with site disorder within a homogeneous sample. Very reasonable intragranular critical currents have been obtained in a sample with a small amount of Nd substituted on the Ba sites, but it is not clear if the Nd plays a direct role in flux pinning. Intergranular critical currents are still quite low due to the large grain size in the high-temperature-processed material and the Nd-deficient layer on the grain boundaries