A method to improve grain boundary current-carrying capability in melt-textured YBa2Cu3O7-δ

A major impediment for many applications of bulk high-Tc superconductors is the extremely low current-carrying capability due to grain boundary weak links. A method has been developed to eliminate secondary phases and reduce microcracks at the grain boundaries in YBCO superconductor by removing a fraction of the liquid phase formed during melt texturing. Samples fabricated using this method consist of large domains containing several grains of oriented platelets with grain boundaries free of secondary phases and microcracks. The processing conditions have been tailored to obtain domains extending over a length of 15 to 20 mm, a width of 8 to 10 mm and a thickness of up to 5 mm. The grain boundary misorientation is characterized by optical microscopy as well as X-ray pole figure analysis. These grain boundaries, though having large misorientation angles up to 27.80 degrees, are found to carry high currents at 77 K, both in self-field and in an applied magnetic field of 1.5 T. These results give promise of the manufacture of polycrystalline YBCO superconductors with high current-carrying capability. (author)