On the incorporation of beryllium into the biotemplated synthesis of YBa2Cu3O7-delta

This work represents the first SQUID (superconducting quantum interference device) magnetometry study on the effect of incorporating beryllium into the synthesis of the high temperature superconductor YBa2Cu3O7-delta (Y123). Through a biopolymer-mediated synthetic approach, the homogeneous nature of the precursor sol and the preferred nucleation and growth of the Y123 phase allow for the greatest possible yield of the superconducting phase. In contrast to a previous report, our finding, through crystallographic studies of the as-synthesized material, is that in spite of a beryllium excess being provided in the precursor, beryllium does not substitute into the Y123 crystal lattice, instead forming an associate phase which comes to dominate at high doping levels, to the detriment of the Y123 phase. In addition, we are able unambiguously to refute the previously reported increase in superconducting transition temperature at low beryllium doping levels.