Powder metallurgical process to enhance the critical current density and critical magnetic field in high entropy alloy superconductors

This review presents the superconducting properties of a representative high entropy alloy (HEA), namely Ta1/ 6Nb2/6Hf1/6Zr1/6Ti1/6. Since the discovery of high entropy alloy superconductor, many HEA superconductors have been reported that mostly focused on arc-melted samples. Recent investigation shows that the superconducting properties are sensitive to the synthesis conditions. Therefore, it is worth noting the superconducting properties depending upon synthesis methods, such as arc melting and powder metallurgy techniques like spark plasma sintering (SPS) and hot press (HP) sintering. This active research areas include understanding the fundamental mechanisms underlying the properties of HEAs and exploring novel compositions and processing methods to enhance their performance. This work highlights explicitly the strong correlation and strong coupling of the s-wave superconducting properties observed in the arc-melted Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 compound. The SPS-sintered Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 compound showed a notable increase in vortex pinning, enhancing critical current density. The dynamics of vortices exhibit unconventional behavior, including the occurrence of magnetic vortex avalanche effects. By comparing superconducting properties depending upon synthesis process, powder metallurgical process for HEA synthesis enhances the critical current density and vortex pinning force with maintaining high mechanical strength, which is beneficial to practical applications in superconducting magnet.