Structural, superconducting and vortex pinning properties of Nb-substituted Bi-2212 ceramic superconductor

Abstract

In this research, we have deeply focused to investigate the effects of Niobium (Nb) substitution for the Ca site in the Bi2Sr2Ca1−xNbxCu2O8+y superconductors with x = 0.00, 0.05, 0.10, 0.20, 0.30, and 0.40. The materials were synthesized via well-known solid state reaction method. We have performed X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and dc magnetization measurements in order to understand the effects of Nb-content. XRD results exhibit that the Bi-2212 phase is a major phase for pure sample. On the other hand, the volume fraction of Bi-2212 declines with increasing Nb substitution and relocates with low-Tc phase, namely Bi-2201. The maximum pinning force, FPmax, values of x = 0.05 and 0.10 Nb-substituted samples are improved in comparison to the pure sample. These values are found as 5.18 × 107 and 5.21 × 107 Oe A/cm2 at T = 10 K for x = 0.05 and 0.10 Nb-substituted sample, respectively, which are higher than the 4.92 × 107 Oe A/cm2 value of the pure sample.