Synthesis and characterization of Eu- and La-doped CuS nanoparticles and their effects on the electrical properties of (Bi,Pb)₂Sr₂Ca₂Cu₃O_δ superconductor

Abstract

Undoped, Eu- and La-doped CuS nanoparticles stabilized by l-cysteine were synthesized by a low-temperature soft aqueous route. Their structural properties were investigated by X-ray powder diffraction, their morphological properties were scrutinized using scanning electron microscopy, their microstructural properties were carried out using transmission electron microscopy, their optical properties were examined using ultraviolet–visible spectroscopy, and their electrical properties were studied using complex impedance spectroscopy. It was found that Cu_0.99La_0.01S nanoparticles exhibit the smallest particle size, the highest optical bandgap, the highest values of electrical conductivity and dielectric constant, and the lowest values of dielectric loss tangent when compared with CuS and Cu_0.99Eu_0.01S nanoparticles. To investigate the effect of the as-synthesized nanoparticles on the superconducting properties of bismuth-based compound ((Bi,Pb)₂Sr₂Ca₂Cu₃O_δ), its structural properties were examined by X-ray powder diffraction, its transport properties were analyzed by the standard four-probe technique, its intrinsic properties were investigated using the Aslamazov–Larkin approach and its pinning properties were studied using the thermally activated flux flow model. It was found that Cu_0.99La_0.01S added sample exhibits the highest Bi-2223 phase concentration, the lowest residual resistivity, the highest critical transition temperature, the lowest value of coherence length, the highest values of penetration depth, upper critical magnetic field and critical current density, the narrowest shift of the zero-resistivity temperature, the highest effective pinning energies and the highest global critical current densities, when compared with pure, CuS and Cu_0.99Eu_0.01S added samples.