Influence of Ni0.5Zn0.5Fe2O4 nanoparticles on the superconducting properties and AC susceptibility of Bi1.6Pb0.7Sr2CaCu2O8 superconductor

The effects of nano-sized Ni_0.5Zn_0.5Fe₂O₄ (NZFO) addition on the superconducting properties of Bi_1.6Pb_0.4Sr₂CaCu₂O₈ (Bi-2212) were investigated. Samples were prepared using the solid-state reaction method with NZFO addition of 0 to 0.5 wt%. The structural, electrical, and magnetic properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistance measurements, and AC susceptibility analysis. All samples exhibited normal metallic characteristics above onset transition temperature, T_c−onset. The resistance versus temperature measurements showed T_c−onset and zero transition temperature, T_c−zero for all samples ranging between 72 and 82 K, and 55 and 70 K, respectively. Scanning electron microscopy (SEM) revealed noticeable microstructural changes with higher additions of nano-sized NZFO. Despite these changes, the addition of nano-sized NZFO did not significantly suppress the intra- and intergrain characteristics of the Bi-2212 phase. The x = 0.06–0.08 wt% samples showed the highest intergrain peak temperatures, Josephson current and Josephson coupling energy even though the transition temperatures and Bi-2212 phase volume fraction were suppressed. This work showed that the appropriate addition of nano-sized NZFO could significantly enhance grain connectivity and critical current density, highlighting its potential as an effective flux pinning center for Bi-based superconductors.