Intrinsic Properties of Nano-CdS-Added YBa₂Cu₃O_y and (Bi,Pb)₂Sr₂Ca₂Cu₃O_δ Superconductors

Abstract

The effect of cadmium sulfide (CdS) nanoparticles synthesized by hydrothermal method on the structural properties and on the excess conductivity of yttrium-based compound (YBa₂Cu₃O_y) and bismuth-based compound ((Bi,Pb)₂Sr₂Ca₂Cu₃O_δ) was reported. The electrical resistivity versus temperature, $\rho (T)$, in the paraconductive region, was analyzed using the Aslamazov–Larkin model. Different fluctuation regions indicated by the short-wave region, mean-field region, and critical region were identified. The coherence length ${\xi }_{c}(0)$, the effective layer thickness $d$, the penetration depth ${\lambda }_{c}(0)$, the lower and upper critical magnetic fields, ${B}_{c1}\left(0\right)$ and ${B}_{c2}\left(0\right)$, the critical current densities ${J}_{c}\left(0\right)$, and numerous other superconducting parameters are determined. It was found that the intrinsic properties are much more improved in the CdS-added samples, which suggests that the addition of CdS nanoparticles in the superconducting matrix leads to the enhancement of the grain connectivity, the formation of strong pinning centers contributing to the reduction of magnetic vortex motion and therefore, the improvement of the conduction properties in the yttrium- and bismuth-based materials.