Effect of CoFe2O4 Addition in the Superconducting and Hardness Characteristics of Bi-2223 Ceramics

This study investigates the influence of CoFe2O4 (CFO) content variation (x = 0.000 to 0.010) on the mechanical, structural and superconducting properties of Bi-2223. Vickers microhardness measurements show a clear decrease in hardness with increasing CFO content. This decrease is linked to grain boundary weakening, structural defects, and impurity phases. Multiple hardness models are applied to analyze the indentation size effect (ISE). The Hays-Kendall model provided the closest fit to plateau region. SEM analysis reveals that higher CFO doping leads to increased grain fragmentation, irregular grain shapes, and reduced grain connectivity. Magnetization versus temperature (M–T) measurements are performed. The critical onset temperature (Tc) decreasing from 109.8 K (CFO-0) to 93.4 K (CFO-5) due to enhanced structural disorder and increased magnetic scattering. In summary, the study reveals that adding CFO leads to a decline in both mechanical and superconducting performance of the Bi-2223 samples. This is mainly because of increased grain boundary defects and magnetic scattering.