Investigation of the mechanical and structural performance of Bi1.6Sr2.0Ca1.1Cu2.1YxO8+& crystalline structures

In this thesis, the main properties of the superconducting crystal systems obtained by adding varying amounts of Y2O3 to the Bi-2212 crystal parent structure were investigated in detail by structural and mechanical analysis. The characteristic structural analysis of the samples was investigated by X-Ray Diffraction (XRD) measurements while the mechanical properties were investigated by Vickers microhardness measurements. The structural analysis for all samples clearly showed that the Bi-2212 high temperature superconducting phase is more dominant than the other superconducting phases. In addition, it was observed that the lattice parameters obtained from X-ray analysis were similar to the lattice parameters of the Bi-2212 main structure. The mechanical parameters such as E, Y, KIC, C11, B and D, which are necessary for industrial and technological applications, were determined by load-dependent Vickers microhardness measurements. Moreover, it was determined that the microhardness values of all samples gradually increased with the amount of indentation test load applied and showed the Reverse Indentation Size Effect (RISE) behavior. Furthermore, Vickers microhardness measurements and six different theoretical approaches such as Meyer's law, Proportional Specimen Resistance (PSR) model, Modified Proportional Specimen Resistance (MPSR) model, Elastic/Plastic Deformation (EPD) model, Hays-Kendall (HK) model and Indenter Induced Cracking (IIC) model were used to calculate the load-independent microhardness of the specimens and compared with experimental microhardness measurements. As a result, it was observed that the Indenter Induced Cracking (IIC) approach is the most suitable theoretical approach for determining the load-independent microhardness values of the samples for all the samples prepared within the scope of this thesis.