Improving Mechanical Strength of YBCO Bulk Superconductors by Addition of Ag

Abstract

The widespread use of ceramic (RE)Ba2Cu3O7 bulk superconductors (RE-123), where RE=Y, Gd or Sm, is generally hindered by their poor mechanical properties. While a large number of techniques can be used to improve the mechanical properties of conventional ceramic materials, many of these are incompatible with the growth of single grain, bulk RE-123 super- conductors using the top seeded melt growth (TSMG) process. Complications arise due to the need to minimize the degradation of the superconducting properties and produce a single-grained sample. Nonetheless, the addition of Ag to RE-Ba-Cu-O [(RE)BCO] precursor powder has been demonstrated to be effec- tive in improving the mechanical properties of single grain bulk superconductors fabricated by TSMG without deleterious effects on performance. Although large single grains of GdBa2Cu3O7-Ag and SmBa2Cu3O7-Ag have been successfully and reliably grown, it has proven more difficult to grow large single grains of YBa2Cu3O7-Ag. We recently demonstrated the growth of single grain YBa2Cu3O7-Ag bulk superconductors that exhibit relative- ly good superconducting properties. In this work, we report the flexural stress at a number of locations within YBa2Cu3O7 single grains grown by TSMG with and without additional liquid phase and with silver addition. In addition, we have compared the dis- tribution of the failure stress with the pore and silver distribu- tion.