Improving Mechanical Strength of YBCO Bulk Superconductors by Addition of Ag

Abstract

The widespread use of ceramic (RE)Ba 2 Cu 3 O 7 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 superconductors 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 effective in improving the mechanical properties of single grain bulk superconductors fabricated by TSMG without deleterious effects on performance. Although large single grains of GdBa 2 Cu 3 O 7 -Ag and SmBa 2 Cu 3 O 7 -Ag have been successfully and reliably grown, it has proven more difficult to grow large single grains of YBa 2 Cu 3 O 7 -Ag. We recently demonstrated the growth of single grain YBa 2 Cu 3 O 7 -Ag bulk superconductors that exhibit relatively good superconducting properties. In this work, we report the flexural stress at a number of locations within YBa 2 Cu 3 O 7 single grains grown by TSMG with and without additional liquid phase and with silver addition. In addition, we have compared the distribution of the failure stress with the pore and silver distribution.