Superconductivity in thermally annealed Ta-Nb-Hf-Zr-Ti high-entropy alloys

Vrtnik, S.; Koželj, Primož; Meden, Anton; Maiti, Soumyadipta; Steurer, Walter; Feuerbacher, M.; Dolinšek, J.

doi:10.1016/j.jallcom.2016.11.417

Cited by 109 publications

(69 citation statements)

References 16 publications

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“…These measurements have shown that the coefficient γ of the electronic contribution to LTSH, which is proportional to dressed DOS at E F , N γ (E F ) structural change obey the Dynes-Varma correlation [58] which seems valid for all disordered transition metal alloys, both crystalline (e.g., [21,23]) and amorphous [43]. As already noted in [24], since N γ (E F ) is enhanced by the electron-phonon interaction, it cannot be used to prove that the changes in figure 4 for x > 0.35 are due to change in N 0 (E F ).…”

Section: Resultsmentioning

confidence: 93%

“…However, present research of HEAs seems somewhat uneven, with the main effort invested in the development of new structural materials, thus focused on their mechanical properties, microstructure and thermal stability (e.g., [5,14,17]). Meanwhile, the research aimed at their electronic structures and properties, both experimental [5,18,19,20,21,22,23,24] and theoretical [5,25,26,27,28,29], is in spite of their potential as functional materials [5] still insufficient. The lack of insight into their electronic structure which in metallic systems determines almost all their properties (e.g., [30,31]) hinders the conceptual understanding of both crystalline (c-) and amorphous (a-) HEAs [19,24].…”

Section: Introductionmentioning

confidence: 99%

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Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)1−xNi alloys

Kuveždić

Tafra

Basletić

et al. 2020

Journal of Non-Crystalline Solids

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We present results of comprehensive study of electronic properties of (TiZrNbCu) 1−x Ni x metallic glasses performed in broad composition range x encompassing both, high entropy (HE) range, and conventional Ni-base alloy concentration range, x ≥ 0.35. The electronic structure studied by photoemission spectroscopy and low temperature specific heat (LTSH) reveal a split-band structure of density of states inside valence band with d-electrons of Ti, Zr, Nb and also Ni present at Fermi level N (E F ), whereas LTSH and magnetoresistivity results show that variation of N (E F ) with x changes in Ni-base regime. The variation of superconducting transition temperatures with x closely follows that of N (E F ). The electrical resistivities of all alloys are high and decreasewith increasing temperature over most of explored temperature range, and their temperature dependence seems dominated by weak localization effects over a broad temperature range (10 − 300 K). The preliminary study of Hall

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)1−xNi alloys

Kuveždić

Tafra

Basletić

et al. 2020

Journal of Non-Crystalline Solids

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“…High-temperature synthesis methods, such as arc-melting, are commonly used for the preparation of HEA superconductors. These methods are prone to form intermetallic phases instead of randomly mixed lattice sites of HEA [22]. Hence, very high melting temperatures and high quenching rates have to be employed for the preparation of single phase HEAs, which correspondingly lead to a low crystallinity of the samples.…”

Section: Resultsmentioning

confidence: 99%

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Zhang

Winter

Witteveen

et al. 2020

Phys. Rev. Research

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We report on the preparation and the physical properties of superconducting (TaNb) 1− (ZrHfTi) high-entropy alloy films. The films were prepared by means of magnetron sputtering at room temperature, with ranging from 0 to 1 with an average thickness of 600 -950 nm. All films crystallize in a pseudo body-centered cubic (BCC) structure. For samples with < 0.65, the normal-state properties are metallic, while for ≥ 0.65 the films are weakly insulating. The transition from metallic to weakly insulating occurs right at the near-equimolar stoichiometry. We find all films, except for = 0 or 1, to become superconducting at low temperatures, and we interpret their superconducting properties within the Bardeen-Cooper-Schrieffer (BCS) framework. The highest transition temperature Tc = 6.9 K of the solid solution is observed for ~0.43. The highest upper-critical field Bc2(0) = 11.05 T is found for the near-equimolar ratio ~0.65, where the mixing entropy is the largest. The superconducting parameters derived for all the films from transport measurements are found to be close to those that are reported for amorphous superconductors. Our results indicate that these films of high-entropy alloys are promising candidates for superconducting device fabrication.

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“…In this respect, a polymorphic transition may occur for some x value upon proper thermal treatment. It is worth noting that, even for the Al-free Ta-Nb-Zr-Hf-Ti HEAs, the bcc structure can be unstable against annealing, though no other polymorph has been observed [31]. This suggests that the occurrence of structure polymorphism in HEAs is closely related to their constituent elements.…”

Section: Resultsmentioning

confidence: 99%

Polymorphism and superconductivity in the V-Nb-Mo-Al-Ga high-entropy alloys

Liu

Cui

et al. 2020

Sci. China Mater.

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High-entropy alloys (HEAs) are at the focus of current research for their diverse properties, including superconductivity and structural polymorphism. However, the polymorphic transition has been observed only in nonsuperconducting HEAs and mostly under high pressure.Here we report the discovery of superconductivity and temperature-driven polymorphism in the (V0.5Nb0.5)3−xMoxAl0.5Ga0.5 (0.2 ≤ x ≤ 1.4) HEAs. It is found that the as-cast HEA is of a single body-centered cubic (bcc) structure for x = 0.2 and a mixture of the bcc and A15 structures for higher x values. Upon annealing, the bcc structure undergoes a polymorphic transformation to the A15 one and all HEAs exhibits bulk superconductivity. For x = 0.2, whereas the bcc polymorph is not superconducting down to 1.8 K, the A15 polymorph has a superconducting transition temperature Tc of 10.2 K and and estimated zero-temperature upper critical field Bc2(0) of 20.1 T, both of which are the highest among HEA superconductors. With increasing Mo content x, both Tc and Bc2(0) of the A15-type HEAs decrease, yet the large ratio of Bc2(0)/Tc signifies a disorder-induced enhancement of the upper critical field over a wide x range. The decrease in Tc is attributed to the decrease in both the electronic specific-heat coefficient and electron-phonon coupling strength. Furthermore, the valence electron count dependence of Tc, which is different from both the binary A15 and other structurally different HEA superconductors, suggests that Tc may be increased further by reducing the number of valence electrons. Our results not only uncover HEA superconductors of a new structural type, but also provide the first example of polymorphism dependent superconductivity in HEAs. PACS numbers:

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Superconductivity in thermally annealed Ta-Nb-Hf-Zr-Ti high-entropy alloys

Cited by 109 publications

References 16 publications

Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)1−xNi alloys

Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)1−xNi alloys

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Polymorphism and superconductivity in the V-Nb-Mo-Al-Ga high-entropy alloys

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