Y(1-x)ho(x)ba(2-y)nd(y)cu(3)o(7-δ) süperiletken malzemelerin mekanik ve süperiletkenlik özelliklerinin deneysel ve teorik metotlarla incelenmesi

This comprehensive study reports the effect of the Ho, Nd and co-doping inclusions on the microstructural, electrical, mechanical and superconducting characteristics of YBa2Cu3O7-δ ceramic superconductors with the aid of standard characterization methods including the bulk density, dc resistivity, transport critical current density, X-ray diffraction, electron dispersive spectroscopy, scanning electron microscopy and vickers microhardness investigations. The experimental results such as the degree of granularity, hole localization effect, room temperature resistivity, critical transition temperature, degree of the broadening, thermodynamic fluctuations, crystallinity, crystal plane alignments, crystal structure, grain size, phase purity and lattice parameters, appearance of flux pinning centers, grain boundary weak-links, surface morphologies, real microhardness values, elemental compositions and distributions belonging to the pure, Y-site Ho and Ba-site Nd substituted Y-123 superconducting samples are discussed in detail for the first time. Moreover, mechanical characterization enables us to theoretically determine the elastic modulus and yield strength being in charge of the potential mechanical applications. Additionally, the load dependent microhardness values of the samples have not been modeled by the available theoretical methods (Hays–Kendall and indentation-induced cracking approach) up to the present. All the experimental findings show that the microstructural, electrical, mechanical and superconducting properties improve regularly with the increment in the Ho concentration level at the Y-site in the YHo, in the Nd concentration level at the Ba-site in the YNd and in the Nd concentration level at the Ba-site and in the HcN (Ho constant+Nd changeble) until a certain value of x=0,100,y=0,250 and y=0,100, respectively,beyond which and with the increment in the Ho concentration level at the Y-site in the NcH (Nd constant+Ho changeble), the characteristics tend to retrograde rapidly. This is attributed to the fact that excess penetration of the Ho and Nd damages the crucial properties given above. Furthermore, all the samples exhibit the typical reverse indentation size effect behavior under the applied indentation test load. The vickers microhardness measurement evidences also declare that the plastic deformation is superior to the elastic deformation. Based on the results, the IIC model is superior to HK approach for the description of the real microhardness values belonging to all the superconducting samples.