Enhancement of critical currents and trapped fields of melt textured ZnO doped Dy-Ba-Cu-O bulk superconductors

We investigated the effect of Zn on the superconducting properties of c-axis oriented, 30 mm in diameter, single domain Dy-Ba-Cu-O (DyBCO) bulk superconductors fabricated with a top-seeded melt growth process in air using Nd-Ba-Cu-O as a seed crystal. It was observed that the superconducting transition temperature (T-c) decreased monotonically with Zn doping compared to that of the undoped DyBCO sample. A pronounced peak effect with high critical current density (J(c)) was observed in the field range of above 1.5 T for an optimal Zn doped DyBCO sample and the peak position shifted to lower fields with increasing the Zn-content. The maximum trapped magnetic flux density (B-max) of Zn-free DyBCO bulk sample was found to be 0.77 T, and 0.83 T for an optimal Zn doped DyBCO at 77 K. These results suggest that a small amount of Zn plays an important role in enhancing both J(c) and trapped field and the peak effect is comparable to those of the LRE-Ba-Cu-O system (LRE: light rare earth element, Nd, Sm, Eu and Gd) and more pronounced than that of the YBCO system. (C) 2004 Elsevier B.V. All rights reserved.