Superconducting High Entropy Alloy under High Pressures

High-entropy alloys (HEAs) are a class of multi-element materials that exhibit unique structural and functional properties. This study reports the synthesis and characterization of a superconducting HEA, (NbTa)_0.55(HfTiZr)_0.45 fabricated using vacuum arc melting. X-ray diffraction (XRD) analysis revealed a single-phase body-centered cubic (BCC) crystal structure. This HEA superconductor was investigated by XRD at HPCAT, Advanced Photon Source and the BCC phase was stable to the highest pressure of 50 GPa. Superconductivity was characterized by four-probe resistivity measurements in a Quantum Design physical property measurement system (PPMS), yielding a superconducting transition temperature (T_c​) of 7.2 K. The upper critical field (Hc₂) was determined to be 9.5 T. Further investigations into the pressure-dependent superconducting behavior were conducted in the pressure range of 1 GPa to 24 GPa. The results demonstrated increased T_c​ with pressure, reaching a maximum of 10.1 K at the highest applied pressure of 24 GPa. In addition to its superconducting properties, the mechanical performance of (NbTa)_0.55(HfTiZr)_0.45 was evaluated through nanoindentation measurements, revealing a mean hardness of 6.4 GPa and a mean Young's modulus of 132 GPa. The combination of high structural stability, enhanced superconducting performance under pressure, and superior mechanical properties highlights (NbTa)_0.55(HfTiZr)_0.45 ​ as a promising superconductor under extreme environments.