Microstructural and excess conductivity properties of Y-123: effect of organic polymer chitosan inclusion

This research investigated the effect of chitosan as fine nucleation for the interactions among surface microstructure, secondary phases, and thermodynamic fluctuations of superconducting parameters during the superconducting transitions in YBa₂Cu₃O_7-δ (Y-123) system. The study involved incorporating various low concentrations (0.0100 wt.% ≤ x ≤ 0.6000 wt.%) of chitosan (CHI) extracted from marine waste into the Y-123 matrix through a thermal treatment method annealed in an oxygen atmosphere. XRD results showed that all specimens crystallized into orthorhombic Y-123 as the main phase, with non-superconducting phases such as Y-211 and BaCuO₂. These additions introduced different trends in grain degradation and appearance of nano-entities within the Y-123 matrix system. Investigations into the excess conductivity through DC resistivity measurements of these bulk granular specimens revealed a complete reduction in inter-layer coupling while preserving oxygen content and grain size. Furthermore, superconducting transition temperatures (T_c-onset, T_c-offset), superconducting transition width (ΔT_c), and intergranular current density at zero temperature (J_c(0)) experienced significant improvements at lower concentrations, reaching an optimum at 0.0100 wt.%. The J_c(0) reached its peak value at 8.17 × 10⁶ A/m² for the specimen with 0.0100 wt.% CHI addition annealed in an oxygen atmosphere. This research underscores the potential of a sustainable approach involving the incorporation of low-concentration organic polymer (CHI), aligning with the principles of green materials and the advancement of superconductivity.