Effect of Yb addition on the superconducting properties of (Bi,Pb)-2212 superconductor

Abstract

The effects of Yb addition on the phase evolution and superconducting properties of (Bi,Pb)-2212 superconductor prepared by solid state synthesis in the polycrystalline form were studied. Yb content of the samples was varied ( x = 0–0.5) on a general stoichiometry of Bi 1.7Pb 0.4Sr 2.0Ca 1.1Cu 2.1Yb x O y . Phase analysis by XRD, microstructural examination by SEM, measurements of density and superconducting properties were done to evaluate the relative performance of the samples. A Yb containing secondary phase could be distinguished from XRD analysis from Yb > 0.3 in the stoichiometric level. Microstructural examination showed clear and distinct morphological variation with Yb stoichiometry and a secondary phase with round edged grains was observed in the microstructure of Yb added samples. The critical current density ( J C) and superconducting transition temperature ( T C) of all the Yb added samples were found to be higher than that of the pure sample. A maximum T C-onset of 94.5 K and a maximum J C 688 A/cm 2 has been observed for the sample with Yb = 0.2 in the stoichiometric level. Above this level T C and J C began to reduce, may be due to secondary phase formation.