Structural and superconducting properties of Bi-Sr-Ca-Cu superconductors studied by Fe doping

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Abstract
1.5% of Fe has been substituted for Cu in several ‘‘2212’’ and ‘‘2223’’ Bi‐Sr‐Ca‐Cu superconductors. All of the samples show a reduction of Tc by about 13 K due to the Fe impurities. Mössbauer measurements at room temperature reveal structural characteristics such as stacking faults and intergrowth of different phases in these Bi‐based compounds on the microscopic scale. The suppression of Tc due to Fe doping in the Bi ‘‘2212’’ or ‘‘ 2223’’ system is comparable to that of the ‘‘123’’ system, but much smaller than that of the ‘‘214’’ system. The interplanar correlation existing in the ‘‘123’’ and the Bi ‘‘2212’’ and ‘‘2223’’systems seems to play an important role in sustaining the high‐temperature superconductivity and weakening the detrimental effect of impurity elements on superconductivity in these two systems.