Structural evolution and superconductivity tuned by valence electron concentration in the Nb-Mo-Re-Ru-Rh high-entropy alloys. (20th September 2021)

• Record Type: Journal Article
• Authors: Liu, Bin; Wu, Jifeng; Cui, Yanwei; Zhu, Qinqing; Xiao, Guorui; Wu, Siqi; Cao, Guang-han; Ren, Zhi
• Is Part Of: Journal of materials science & technology. Volume 85(2021)
• Page Start: 11
• Page End: 17
• Publication Date: 2021-09-20
• Subjects: High-entropy alloys -- Hcp to α-Mn structural evolution -- Superconducting properties -- Valence electron concentration -- Electronegativity difference; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.02.002
• Languages: English
• ISSNs: 1005-0302

Abstract

Abstract: The crystal structure and physical properties of Nb25 Mo5+ x Re35 Ru25 -x Rh10 (0 ≤ x ≤ 10) and Nb5 Mo35 -y Re15+ y Ru35 Rh10 (0 ≤ y ≤ 15) high-entropy alloys (HEAs) have been studied by X-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. The results show that the former HEAs with valence electron concentration (VEC) values of 6.7–6.9 crystallize in a noncentrosymmetric cubic α-Mn structure, while the latter ones with VEC values of 7.1–7.25 adopt a centrosymmetric hexagonal close-packed (hcp) structure. Despite different structures, both series of HEAs are found to be bulk superconductors with a full energy gap, and the superconducting transition temperature T c tends to decrease with the increase of VEC. Nevertheless, the T c values of the hcp-type HEAs are higher than those of the α-Mn-type ones, likely due to a stronger electron phonon coupling. Furthermore, we show that VEC and electronegativity difference are two key parameters to control the stability of α-Mn and hcp-type HEAs. These results not only are helpful for the design of such HEAs, but also represent the first realization of structurally different HEA superconductors without changing the constituent elements.