Speaker
Description
High Entropy Alloys (HEAs) are solid solutions of five or more elements mixed in non-negligible proportions. Their unique and very promising physical properties have attracted much attention since their discovery in $2004$. HEAs form well-defined, close-packed structures (BCC, FCC, HCP). Due to their structural features, HEAs are known for exceptional mechanical properties, thermal stability, and corrosion resistance. These materials have enormous potential for various applications, especially if their high durability is combined with more sophisticated phenomena, such as magnetic ordering and superconductivity. Superconductivity in HEAs was discovered in $2014$. Superconducting HEAs are the new category of disordered superconductors that exhibit substantial robustness against environmental perturbations, i.e., great stability in high pressures and at extreme temperatures. Such properties make them a perfect candidate for high-field magnets in LHC, ITER, or NMR applications.
We present the first results of the synthesis, structural and physical characterization of two new refractory Ti-rich HEA superconductors with Y-addition: Ti$_{0.50}$(YNbTaHf)$_{0.50}$ and Ti$_{0.50}$(ZrNbYHf)$_{0.50}$, possessing a high upper critical field $H_{c_2}$. The alloys were prepared by the arc melting method. The structure of alloys was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDXS). Superconductivity was investigated via electrical resistivity, AC susceptibility, DC magnetization, and specific heat measurements. Additionally, computational calculations within density-functional theory (DFT) were performed. The effect of yttrium on the microstructure and superconducting properties was examined and compared to our previous work on first Ti-rich HEA superconductors [1]. The results showed that both alloys crystallize in a dual-phase structure, dominated by BCC, with a small fraction of HCP. The determined superconducting transition temperatures $T_c$ for Ti$_{0.50}$(YNbTaHf)$_{0.50}$ and Ti$_{0.50}$(ZrNbYHf)$_{0.50}$ are $7$ K and $5$ K, respectively. The relatively high upper critical field of both alloys ($H_{c_2}>13$ T) makes them a new group of potential candidates for high-field magnet applications.
References
[1] P. Sobota et al., “New type of Ti-rich HEA superconductors with high upper critical field,” Acta Materialia, vol. 285. Elsevier BV, p. 120666, Feb. 2025. https://doi.org/10.1016/j.actamat.2024.120666
