On the incorporation of beryllium into the biotemplated synthesis ofYBa2Cu3O7−δ

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This work represents the first SQUID (superconducting quantuminterference device) magnetometry study on the effect of incorporatingberyllium into the synthesis of the high temperature superconductorYBa2Cu3O7−δ (Y123). Through a biopolymer-mediated synthetic approach, the homogeneous nature ofthe precursor sol and the preferred nucleation and growth of the Y123 phase allow for thegreatest possible yield of the superconducting phase. In contrast to a previous report,our finding, through crystallographic studies of the as-synthesized material, isthat in spite of a beryllium excess being provided in the precursor, berylliumdoes not substitute into the Y123 crystal lattice, instead forming an associatephase which comes to dominate at high doping levels, to the detriment of theY123 phase. In addition, we are able unambiguously to refute the previouslyreported increase in superconducting transition temperature at low beryllium dopinglevels.