Structural and Mechanical Dynamics of Y-358 Superconductors Influenced by Tb/Y and Zn/Cu Substitutions

The search for superconductors with superior mechanical properties has driven research into homovalent replacements. In this work, we have systematically incorporated Tb/Y and Zn/Cu dopants into Y_3-x(Tb)_xBa₅Cu₈O_18-δ and Y₃Ba₅Cu_8-x(Zn)_xO_18-δ based bulk superconductors using the sol-gel technique. Our goal was to explore the fundamental mechanisms linking dopant concentration (0–15%), substitution, processing, and mechanical performance. Understanding these mechanisms can help in designing robust and high-performance superconducting materials for various technological applications. The samples were extensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness measurements and related calculations. The hardness data were further evaluated using Meyer’s law, the proportional sample resistance (PSR) model, the elastic/plastic deformation (EPD) model, the Hays-Kendall (HK) approach, and the indentation-induced cracking (IIC) model. This study reveals the fundamental changes in the properties of Y-358 superconductors due to Tb/Y and Zn/Cu substitutions. The interpretation of the XRD study results leads to the conclusion that all samples have an orthorhombic crystal structure. XRD results confirmed that all samples maintained an orthorhombic crystal structure. However, significant XRD peaks indicated that Tb doping above 10% introduced impurities. Additionally, micromechanical studies demonstrated that hardness values in the plateau region consistently decreased as Tb and Zn doping ratios increased. A decrease in hardness values with increasing applied load, known as the indentation size effect (ISE), was also observed. Among the modeling techniques applied, the IIC model provided the best fit for the hardness test results.