The effect of very high barium content in the precursor on the properties of GdBCO single grain bulk superconductors

A new melt processing route for the fabrication of large grain Gd-Ba-Cu-O (GdBCO) bulk superconductors has been developed based on the use of novel GdBa₄Cu₃O_8−δ (Gd-143) and GdBa₆Cu₃O_10−δ (Gd-163) precursor compositions. The new processing route enables the fabrication of large single grains from precursor powders that contain high concentrations of Ba. The superconducting properties and microstructures of GdBCO single grains with extra Ba fabricated via this new processing route are reported. Most importantly, the possible formation of a new form of Gd_1+xBa_2−xCu₃O_7−δ solid solution (Gd-123ss) with x < 0 in single grains fabricated from the Ba-rich precursor are discussed for the first time based on the superconducting, chemical, and structural properties of the large GdBCO grains.