Akademik Veri Yönetim Sistemi
Journal of Materials Science: Materials in Electronics, cilt.37, sa.6, 2026 (SCI-Expanded, Scopus)
This work examines the structural, electrical, and magnetic behaviour of Bi-2212 superconductors co-doped with sodium and lithium, prepared by the conventional solid-state reaction method. Bulk ceramic samples with fixed sodium substitution at the calcium site (y = 0.05) and varying lithium content at the copper site (x = 0.00–0.20) were produced and analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), DC resistivity, and magnetic techniques. XRD analysis confirmed the dominance of the Bi-2212 phase with minor Bi-2201 and Bi-2223 traces, while Li incorporation promoted the growth of (00 l) planes and induced a slight monotonic expansion of the lattice parameters and crystallite size. SEM observations revealed that Na–Li co-doping enhanced grain growth and reduced porosity, leading to improved intergranular connectivity. EDS analysis confirmed the preservation of the Bi-2212 phase composition and revealed a slight decrease in oxygen concentration in Li-doped samples, indicating oxygen deficiency, in agreement with previous reports and the observed c-axis elongation from XRD analysis. Resistivity measurements indicated that optimal doping (Na05–Li10) resulted in the lowest residual resistivity (1.59 mΩ·cm) and the highest superconducting transition temperatures (Tconset = 85.4 K, Tcoffset = 75.28 K). Magnetoresistance data analysed within the thermally activated flux flow (TAFF) framework showed increased vortex activation energies and improved flux pinning with co-doping. Both the irreversibility field Hirr(0) and the upper critical field Hc2(0) were significantly enhanced, reaching 25.94 T and 48.55 T, respectively, for the Na05–Li10 composition. Magnetic measurements showed enhanced remanent magnetization, increased critical current density (Jc), and stronger flux pinning force, consistent with improved vortex immobilization in the Na–Li co-doped Bi-2212 system. These results indicate that sodium–lithium co-doping significantly enhances the microstructural and superconducting characteristics of Bi-2212, thereby extending its suitability for high-field applications.