Samaryumun ile bizmut yer değişiminin bi-2223 süperiletken seramiklerinin transport ve magnetoresistans özellikleri üzerine etkisi

The aim of this study is to examine the effects of Sm subsititution with Bi on the structural and superconducting properties of Bi-2223 ceramics with the aid of the DC electrical resistivity, critical current density, XRD, and SEM measurements. One of the most important progresses has been achieved in enhancing the transport properties of this high-Tc superconductor with DC electrical resistivity since the discovery of Bi-2223 superconductor. Besides the measurements of XRD are used to understand both lattice parameters and phase composition. The images of scanning electron microscopy (SEM) are used for microstructure examination. The substitution of Sm with Bi on Bi-2223 is performed with changing the concentration of Sm as x = 0, 0.01, 0.03, 0.05 0.07, 0.1 and 0.3. The superconducting samples were synthesized by the solid state reaction method to obtain information about the growth techniques. Solid state reaction method is the conventional method to prepare superconductors. The critical temperature was increased until the concentration of Sm x=0.3. The samples studied in this study are prepared by conventional solid-state reaction method at the annealing temperature of 840°C for 48h. For the potential technological and industrial applications, the important characteristics such as the normal state resistivity, density, porosity, critical (onset and offset) transition temperature, variation of critical temperature, self field critical current density, crystallinity, phase purity, lattice parameter, texturing, surface morphology, Vickers microhardness and elastic modulus values are obtained for the pure and Sm substituted samples and compared with each other. At the same time, the Vickers microhardness values indicate that the samples (towards optimally doped state) exhibit Reverse Indentation Size Effect (RISE) behavior. As for SEM images, similar to the XRD investigations, the former sample has the best crystallinity, texturing, grain connectivity, lowest porosity and largest grain size while the worst surface morphology is observed for the latter sample. Additionally, the bulk porosity analyses for the samples demonstrate that the bulk porosity decreases monotonously with the Sm content in the Bi-2223 system up to x=0.1 after which the porosity starts to increase regularly towards to maximum value, leading to the degradation of the grain connectivity.