The effect of Ag-doping on the magnetic behaviour of Bi–(Pb)–Sr–Ca–Cu–O ceramic superconductors

Abstract

AC susceptibility χ′( T, H ac) and χ″( T, H ac) measurements have been carried out on rectangular bar shaped high-temperature superconductors with nominal composition of Bi 1.6Pb 0.4Sr 2Ca 3Cu 4− x Ag x O 12 ( x=0–1.0) prepared by the solid state reaction method. The effect of Ag-doping on the Bi–(Pb)–Sr–Ca–Cu–O system has been investigated in terms of an AC susceptibility study. It was found that as the amount of Ag doping increases, the critical current density decreases. We also qualitatively discuss experimental results in the framework of the critical state model (CSM). Comparison of the observations and the results of the CSM suggests the Bean like dependence of the intergrain (matrix) depinning critical current density j cm on the magnetic flux density B in the low field range studied. The temperature dependence of the pinning strength parameter α( T) obtained from AC dissipation is in good agreement with the relation α= α 0(1− T/ T c) 2.37 for undoped Bi–(Pb)–Sr–Ca–Cu–O.