Influence of lead fluoride on the mechanical properties of (${\text{Cu}}_{0.5}{\text{Tl}}_{0.5}$): 1223 Phase

This work reveals the influence of lead fluoride substitution and liquid nitrogen immersion on the mechanical properties of high-temperature superconductor samples $\left({\text{Cu}}_{0.5-x}{\text{Tl}}_{0.5}{\text{Pb}}_x\right){\text{Ba}}_2{\text{Ca}}_2{\text{Cu}}_3{\text{O}}_{10-\delta -y}{\text{F}}_y$, with (0.00 ≤ x ≤ 0.10). The samples under investigation were synthesized by solid-state reaction method at normal pressure. The samples were characterized using X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The X-ray data have indicated that the partial replacement of ${\text{Cu}}^{2+}$ ions by Pb²⁺ ions and oxygen by fluorine in the reservoir layer do not alter the tetragonal structure of the samples. On the other hand, the values of the lattice parameters a and c were found to be varied with x according to the difference in the ionic radii of ${\text{Pb}}^{2+}{\text{and Cu}}^{2+}$ as well as to the oxygen content. SEM analysis has revealed that lead fluoride substitutions improve the inter-grains connectivity of the prepared samples. The values of the superconducting transition temperature ($T_{\text{c}}$) were determined using ac magnetic susceptibility measurements. Vickers microhardness $\left(H_{\text{v}}\right)$ was measured as a function of applied loads and the immersion time in liquid nitrogen (t). It was found that $H_{\text{v}}$ values have recorded enhancements after one-hour immersion in liquid nitrogen. Moreover, the variation of $H_{\text{v}}$ has shown an enhancement about 34% for x = 0.06. Furthermore, various models were employed to interpret the load dependence behavior of H_v.