Thermal-driven gigantic enhancement in critical current density of high-entropy alloy superconductors

The high-entropy alloy (HEA) superconductor, Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 (Ta-Nb-Hf-Zr-Ti), is systematically studied to examine changes in superconducting critical properties, critical temperature (T-c), critical current density (J(c)), and upper critical field (H-c2), concerning thermal treatment conditions. Annealing condition affects J(c) more significantly than T-c and H-c2, with a large improvement of flux pinning force density (F-p). The J(c) of bare sample is reduced to 10 A cm(-2) at an applied magnetic field of approximately 1.5 T, whereas the sample annealed at 550 degree celsius for 12 h exhibits J(c) > 100 kA cm(-2) up to around 4 T. Furthermore, the Vickers hardness (HVIT) of the Ta-Nb-Hf-Zr-Ti HEA superconductor notably increases from similar to 384 to 528 HVIT following a 24-h annealing at 500 degree celsius. These results demonstrate that thermal annealing is a powerful process to optimize both the superconducting and mechanical properties of high-entropy alloy superconductors. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.