Influence of Fe/Ca substitute on fundamental properties of Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy materials

Abstract

In the present study, the role of Fe/Ca partial replacement in Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy (Bi-2223) superconducting material on the crystallinity, electrical, structural morphology and superconducting properties is studied by way of the electrical resistivity (ρ-T), powder X-ray diffraction (XRD), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) measurements. According to the experimental results, the Fe additives are effectively replaced by the Ca sites in the bulk Bi-2223 superconducting system, verified by evidenced by the ρ-T and EDX results. Further, the SEM images show that the crystallinity quality and surface morphology view undermine considerably with the enhancement in the Fe/Ca partial substitution level in the Bi-2223 system because of nonuniform surface appearance with new induced permeant structural deformations, impurity residues, misorientations of grains and systematic problems in the grain boundary couplings in the superconducting system. Additionally, the disappearance or appearance of some diffraction peaks in the XRD pattern as well as the decrease in the c-axis length and increase a-axis length provides the deviation of the Bi-2223 materials from stabilization in the system because of the degradation in the crystal structure quality. Besides, the dc electrical results represent that the electrical and fundamental superconducting characteristics decrease with the increase of Fe/Ca replacement owing to the increment of inhomogeneities in the oxidation state, structural problems and mobile hole carrier concentration in the bulk Bi-2223 materials.