Enhanced flux pinning in (Bi, Pb)-2223 superconductor by Nd addition

Bi1.8Pb0.35Sr2.0Ca2.1Cu3.1NdxOy (x = 0.00, 0.010, 0.020 and 0.030) superconductors were prepared in bulk form. Phase analysis by XRD, microstructural examination by SEM, superconductivity measurements at 77 K, etc were carried out to evaluate the relative performance of the samples. Both the self-field J(C) and J(C) in the presence of an applied magnetic field of the Nd-added samples are found to be much better than those of the undoped one. Also the peak value of the bulk pinning force density, F-p max, of Nd-added samples get shifted towards higher magnetic fields, indicative of enhanced flux pinning strength in these samples. For sample with Nd = 0.030, small fractions of (Bi, Pb)-2212 were found even after the last stage of sintering. Accordingly the microstructure of this sample shows considerable difference from the other samples, wherein the natural layered growth mechanism of (Bi, Pb)-2223 is disrupted by grain growth and coarsening in random directions. It is likely that Nd ions are substituting at the Ca site, and the point defects thus created act as flux pinners, enhancing the self-field J(C) as well as the J(C)-B characteristics of the Nd-added samples.