Superconductivity in reduced and then reoxidized Nd1.05Ba1.95(Cu1−xFex)3O7−δ

The system Nd 1.05 Ba 1.95 (Cu 1− x Fe x ) 3 O 7− δ (NdFe-123) was studied. Substitution of Fe for Cu suppresses superconducting transition temperature T c more rapidly in the NdFe-123 system than in the comparable YBa 2 (Cu 1− x Fe x ) 3 O 7− δ (YFe-123) system. Samples reduced in argon and then reoxidized in oxygen at 400°C show considerable increases in T c . However, the T c of these reoxidized samples still fall below those of similar YFe-123. Microstructural investigation by electron microscopy, structure from X-ray diffraction and their relationships to superconductivity are developed. Possible mechanisms for the T c variations are discussed.