Achieving Superconductivity Through Reductive Treatments of YSr_2(Cu_(1-x)Fe_x)_3O_y

摘要

In order to obtain massive Fe nano clustering coexisting with superconductivity, the dependence of the structural, magnetic, and superconductive properties of YSr_2(Cu_(1-x)Fe_x)_3O_y (x = 0.13 or x = 0.167) on annealing conditions is explored. Materials are initially prepared by conventional solid state technique with an annealing for two days at T = 1000K and is termed oxygenating preparation (OP). The materials treated by OP method show no signs of superconductivity above 5K. Subsequently, Gd getter annealing is used to control reductions at T = 1000K for four days followed by reoxidation at 800K for 1 h and is termed reducing preparation (RP). For x = 0.13, the RP treatment results in the development of superconductivity with T_(c-onset) = 40K. For x = 0.167, a T_(c-onset) = 30K is achieved. A local thermodynamic model based on the stabilities of various Fe cluster arrangements is used to explain the effect of the thermal treatments.