The influence of silver (Ag) nanopowder incorporation on the electrical resistivity, flux-pinning ability, structural, crystal quality, surface morphology, superconducting properties, and mechanical performance of Bi2.1-xAgxSr2.0Ca1.1Cu2.0Oy (Bi-2212) ceramics was systematically investigated. Electrical transport (ρ-T) measurements revealed an optimal doping level at x = 0.03, where resistivity was minimized, hole-carrier concentration was maximized, and the onset (85.54 K) and offset (84.40 K) critical transitions were enhanced due to improved crystallinity, grain connectivity, and interlayer connection. Powder X-ray diffraction (XRD) and density analyses confirmed that this composition stabilizes the Bi-2223 high-Tc superconducting phase, increases bulk density (6.11 g cm−3), and reduces porosity (3.02%). Scanning electron microscopy (SEM) investigations indicated that in the presence of optimum Ag ions in the Bi-2212 system enhances homogeneous appearance, platelet stacking, particle size, and well-oriented grains, hence improving lattice coherence, grain boundary connection, and microstructural compactness. Beyond this level, excessive Ag incorporation induced impurity phases, lattice distortions, porous structure, and microcracks, resulting in degraded crystallinity, suppressed superconductivity, and reduced densification. Energy-dispersive X-ray spectroscopy (EDX) studies confirmed that Ag successfully entered the main matrix, with NanoAg-2 exhibiting the highest Cu content and the most homogeneous elemental distribution, correlating with optimized microstructure and superconducting pathways. Flux-pinning was markedly enhanced at the optimum doping level, leading to an increase in the critical current density (Jc) from 58 to 71 A cm−2 under self-field conditions at 77 K. The increase in Jc value suggests improved current-carrying capability that may be associated with enhanced flux-pinning effectiveness and/or improved grain connectivity. Mechanical assessments further revealed that at x = 0.03, Bi-2212 ceramics exhibit enhanced microhardness, fracture toughness, and load-carrying ability, primarily due to stabilized tetragonal phase formation, and increased resistance to deformation under applied loads, as confirmed by Vickers hardness profiles and SEM observations of dense platelet-like morphologies and reduced porous structure. In contrast, overdoping (x ≥ 0.07) weakened intergranular bonding and diminished resistance to indentation stresses. Collectively, these results display that controlled Ag nanopowder incorporation (x = 0.03) optimizes the structural integrity, flux-pinning ability, superconducting efficiency, and mechanical strength of Bi-2212 ceramics, while excessive doping compromises phase stability and performance. Consequently, optimizing Ag impurity in the Bi-2212 superconducting matrix is expected to facilitate enhanced performance, thereby advancing its potential for real-world technological applications.

Synergistic effects of Ag nanopowder doping on fundamental performance properties of Bi-2212 ceramics

期刊论文
发表日期：

2026年7月17日

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N. B. Uca,
A. T. Ulgen,
B. Akkurt,
A. S. Erturk,
U. Erdem,
G. Yildirim,
C. Terzioglu

摘要

The influence of silver (Ag) nanopowder incorporation on the electrical resistivity, flux-pinning ability, structural, crystal quality, surface morphology, superconducting properties, and mechanical performance of Bi_2.1-xAg_xSr_2.0Ca_1.1Cu_2.0O_y (Bi-2212) ceramics was systematically investigated. Electrical transport (ρ-T) measurements revealed an optimal doping level at x = 0.03, where resistivity was minimized, hole-carrier concentration was maximized, and the onset (85.54 K) and offset (84.40 K) critical transitions were enhanced due to improved crystallinity, grain connectivity, and interlayer connection. Powder X-ray diffraction (XRD) and density analyses confirmed that this composition stabilizes the Bi-2223 high-T_c superconducting phase, increases bulk density (6.11 g cm⁻³), and reduces porosity (3.02%). Scanning electron microscopy (SEM) investigations indicated that in the presence of optimum Ag ions in the Bi-2212 system enhances homogeneous appearance, platelet stacking, particle size, and well-oriented grains, hence improving lattice coherence, grain boundary connection, and microstructural compactness. Beyond this level, excessive Ag incorporation induced impurity phases, lattice distortions, porous structure, and microcracks, resulting in degraded crystallinity, suppressed superconductivity, and reduced densification. Energy-dispersive X-ray spectroscopy (EDX) studies confirmed that Ag successfully entered the main matrix, with NanoAg-2 exhibiting the highest Cu content and the most homogeneous elemental distribution, correlating with optimized microstructure and superconducting pathways. Flux-pinning was markedly enhanced at the optimum doping level, leading to an increase in the critical current density (J_c) from 58 to 71 A cm⁻² under self-field conditions at 77 K. The increase in J_c value suggests improved current-carrying capability that may be associated with enhanced flux-pinning effectiveness and/or improved grain connectivity. Mechanical assessments further revealed that at x = 0.03, Bi-2212 ceramics exhibit enhanced microhardness, fracture toughness, and load-carrying ability, primarily due to stabilized tetragonal phase formation, and increased resistance to deformation under applied loads, as confirmed by Vickers hardness profiles and SEM observations of dense platelet-like morphologies and reduced porous structure. In contrast, overdoping (x ≥ 0.07) weakened intergranular bonding and diminished resistance to indentation stresses. Collectively, these results display that controlled Ag nanopowder incorporation (x = 0.03) optimizes the structural integrity, flux-pinning ability, superconducting efficiency, and mechanical strength of Bi-2212 ceramics, while excessive doping compromises phase stability and performance. Consequently, optimizing Ag impurity in the Bi-2212 superconducting matrix is expected to facilitate enhanced performance, thereby advancing its potential for real-world technological applications.