Fe0.5Cu0.5(Ba1-xSrx)2YCu2O7+δ (x=0, 0.5, and 1) superconductors prepared by high-pressure synthesis

In this paper, the Fe-containing superconductors Fe0.5Cu0.5Ba2YCu2O7+delta, Fe0.5Cu0.5BaSrYCu2O7+delta, and Fe0.5Cu0.5Sr2YCu2O7+delta were successfully prepared by common solid-state reaction followed with a procedure of high pressure synthesis. The structural change and superconducting properties in (FexCu1-x)BaSrYCu2O7+delta (x=0-1.0) systems were also investigated. Annealing experiments indicate that the occurrence of superconductivity in Fe0.5Cu0.5(Ba1-xSrx)(2)YCu2O7+delta (x=0, 0.5, and 1) systems is mainly induced by the procedure of high-pressure synthesis, which causes the increase of oxygen content and the redistribution of Fe atoms between Cu(1) and Cu(2) sites, but not from possible secondary phase of YBa2Cu3O7-delta, YBaSrCu3O7-delta or YSr2Cu3O7-delta superconductors.