Effect of cobalt-diffusion on mechanical, superconducting and structural properties of Bi-2212 superconducting ceramics produced by conventional solid-state reaction technique

The main aim of this thesis is to determine the effect of Co diffused Bi-2212 superconducting systems on the microstructural, electrical, mechanical and superconducting properties of prepared samples with bulk density, X-ray diffraction (XRD), Dc resistivity (ρ-T), Vickers microhardness and transport critical current density (Jc) experimental methods. Further, the samples for this work are prepared by the conventional solid state reaction technique at the constant temperature of 850 °C for the annealing duration of 24 h. Moreover, all the experimental findings display that the microstructural, mechanical, electrical and superconducting properties suppress with the increment of the Co level in the Bi-2212 superconducting matrix up to Co-2 material. Besides, starting from this level, the crucial characteristics diminish rapidly due to not only the deformation between the Bi-2212 layers and grain boundaries but also the disorder and localization (filling) problem in the crystal structure with the enhancement of Co concentration level. This statement simply illustrate the fact that excess Co penetration on the Bi-2212 superconducting system damages the basic characteristics of the material as mentioned before. Consequently, Co-2 superconducting sample is determined as the best sample between the samples produced due to having the greatest superconducting performance, highest critical current density, largest grain size, best crystallinity and connectivity between superconducting grains.