Investigation of the effect of ta addition to copper side of bismuth-based superconductor on superconductory properties

In this study, the effects of high-valence Ta substitution at the Cu site on the superconducting properties of the Bi₁.₆Pb₀.₄Sr₂Ca₀.₉₂₅Na₀.₀₇₅Cu₂₋ₓTaₓO₈ (x = 0, 0.05, 0.075, 0.10, 0.15, and 0.20) system, synthesized via the conventional solid-state reaction method, were investigated. X-ray diffraction (XRD) analysis revealed that the primary phase in all samples was Bi-2212, with additional diffraction peaks corresponding to minor Bi-2201 and Bi-2223 phases. Furthermore, the lattice parameters of the samples were found to decrease with Ta doping. Scanning electron microscopy (SEM) images showed randomly oriented grains with a mixture of platelet-like and needle-like morphologies. Magnetization measurements indicated that symmetrical M-H loops, characteristic of Type-II superconductors, were observed at 10 K, 20 K, and 30 K in all samples. The remanent magnetization (Mᵣ), an indicator of flux pinning ability, increased with Ta doping, and a similar trend was observed in the critical current density (Jc) values. However, the critical transition temperature (Tₛ) and the first critical magnetic field (Hc₁) decreased with increasing Ta content. These findings suggest that Ta substitution significantly influences the superconducting properties of the Bi₁.₆Pb₀.₄Sr₂Ca₀.₉₂₅Na₀.₀₇₅Cu₂₋ₓTaₓO₈ system. However, to achieve further improvements in superconducting performance, alternative synthesis techniques and more comprehensive characterization studies are required.