Resistive measurements of the inter- and intragranular critical current properties in YBa2Cu3O7−δ/Fe

Abstract

Abstract YBa 2 Cu 3 O 7−δ and Fe- (for Cu) substituted bulk samples were prepared by different methods, i.e. the direct and indirect powder metallurgical method and the citrate method. The samples were characterized by magnetization measurements, X-ray diffraction, TEM, SEM and EDX. Four-probe resistive measurements were executed on the ceramic samples in order to obtain the superconducting transition temperature, T c , as well as the critical current density, J c . These data show the presence of two ‘superconducting’ phases, which can be shown to correspond to the inter- and intragranular properties of the samples. The resistive measurements yield a lower limit of the J c values and, therefore, complement magnetization data reported in the literature. Furthermore, the critical current density, J c , is related to the underlying microstructure and the chemical homogeneity of the sample, which both strongly depend on the preparation method and parameters. In the Y-Ba cuprate superconductors larger critical currents are obtained upon the substitution of Cu by Fe and by the application of the citrate method, which guarantees an extremely homogeneous stoichiometry.