Comparative Study of Superconducting Properties for YBa2Cu3O7-δ Added Ca-Compounds Synthesized Under Different Annealing Conditions

Abstract

This comparative investigation is focused on producing bulk YBa₂Cu₃O_7-d (Y-123) through thermal treatment method, employing two distinct annealing conditions: oxygen flow and ambient conditions. This research explored the potential of using chicken eggshells as a source of calcium compounds (CaO, CaCO₃ and Ca(OH)₂) for Y-123 synthesis, incorporating deficient Ca-compound (CaES) concentrations, such as 0.0100 wt.%. The XRD results showed that the structure of all the samples is orthorhombic. The inclusion of deficient Ca compounds suggested an altered pattern of grain degradation within the Y-123 matrix system, accompanied by the emergence of other non-superconducting phases. The superconducting properties, including electrical resistivity, were examined through electrical resistance measurements.  Unexpectedly, the superconducting characteristics improved upon introducing deficient Ca compounds into the Y-123 system, particularly enhancing the rapidity of annealing at ambient conditions. The hole concentration, p increased in the added CaES samples compared to the non-added Y-123. This increase was observed alongside the narrowest superconducting transition width, approximately DT_c = 2.95 K and DT_c^MF-zero = 1.46 K, specifically for the added CaES at 0.0100 wt.% annealed in ambient conditions, in contrast to CaES annealed in oxygen flow. Additionally, the residual resistivity (r_o) was lowest at 336 µΩcm among all samples. This enhancement improves the superconducting properties, emphasizing the potential for cost savings compared to oxygen flow costs.