Decoupling Intergranular Weak-Links and Intragranular Flux Pinning in Bulk Bi-2212 Superconductors: A Two-Component Exponential Model Approach
DOI:
https://doi.org/10.61326/jaasci.v5i1.495Keywords:
Bi-2212 superconductors, Critical current density, Flux pinning, Intergranular - intragranular Jc , Two-component exponential modelAbstract
In this study, the influence of sintering time on the structural, microstructural and magneto-transport properties of bulk Bi2Sr2CaCu2O8+d (Bi-2212) HTc superconductors synthesized by the solid-state reaction method was investigated using Two-Component Exponential Model. The samples prepared were heat treated at 840 oC for two different sintering durations: 60 h (S60) and 120 h (S120). XRD analyses showed that both samples have tetragonal symmetry and increasing the sintering duration to 120 h markedly reduced secondary impurity phases, such as BiSr3O5.4 and Bi2Ca2O5, thereby enhancing phase purity and crystallographic order. Furthermore, thermally activated oxygen desorption during prolonged heat treatment caused an expansion of the c-axis lattice parameter (from 30.62 Å to 30.68 Å), indicating a transition from the overdoped regime to the optimally doped region. The average crystallite size, estimated using the Scherrer method, increased from 38 nm to 45 nm, while Williamson–Hall analysis revealed a significant reduction in internal strain and defect density. SEM micrographs demonstrated the formation of characteristic platelet-like grain morphology and improved grain interlocking resulting from anisotropic grain growth. Analysis of the transport mechanism based on a semi empirical Two-Component Exponential Model showed that the 120 h sintering protocol not only enhanced the Josephson current transport capability ( ) at the macroscopic level through grain-boundary purification, but also improved the stability of flux pinning centers ( ) at the microscopic level by optimizing nanoscale intragrain defects and oxygen stoichiometry, thereby yielding a dual improvement in high-field magnetic performance.
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