Polymorphism and superconductivity in the V-Nb-Mo-Al-Ga high-entropy alloys
Open accessAbstract
High-entropy alloys (HEAs) are the focus of current research for their diverse properties, including superconductivity and structural polymorphism. However, the polymorphic transition has been observed only in non-superconducting HEAs mostly under high pressure. Here we report the discovery of the superconductivity and temperature-driven polymorphism in (V 0.5 Nb 0.5 ) 3− x Mo x Al 0.5 G 0.5 (0.2 ≤ x ≤ 1.4) HEAs, which are 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 exhibit bulk superconductivity. For the sample with x = 0.2, the bcc polymorph is not superconducting down to 1.8 K, whereas the A15 polymorph has a superconducting transition temperature T c of 10.2 K and estimated zero-temperature upper critical field B c2 (0) of 20.1 T, both of which are the highest among HEA superconductors. With increasing Mo content x , both T c and B c2 (0) of the A15-type HEAs decrease, yet the large ratio of B c2 (0)/ T c signifies a disorder-induced enhancement of the upper critical field over a wide x range. The decrease in T c is attributed to the decrease in both the electronic specific-heat coefficient and electron-phonon coupling strength. Furthermore, the valence electron count dependence of T c , which is different from both the binary A15 and other structurally different HEA superconductors, suggests that T c 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. 高熵合金具有结构多晶型性和超导性, 是当前研究的重点. 然而, 多晶型转变仅在非超导的高熵合金中被观察到, 且大多是在高压条件下. 本文报道了(V 0.5 Nb 0.5 ) 3− x Mo x Al 0.5 Ga 0.5 (0.2 ≤ x ≤ 1.4) 高熵合金中的超导和温度驱动多晶型性. 实验结果表明当 x = 0.2时铸态高熵合金具有单一的体心立方(bcc)结构, 而当 x 值更高时则为bcc和A15的混合结构. 经高温退火后, bcc结构向A15结构进行多晶型转变, 且所有高熵合金均表现出块体超导电性. 对于 x = 0.2的组分,其bcc晶型直到1.8 K仍不具备超导性, 但其A15晶型却在10.2 K表现出超导性, 估算零温上临界磁场 B c2 (0)为20.1 T, 该超导温度 ( T c )和磁场强度在已知的高熵合金超导体中均为最高. 随着Mo含量 x 的增加, A15型高熵合金的 T c 和 B c2 (0)均降低, 但 B c2 (0)/ T c 比值表明在宽的 x 范围内存在无序诱导的上临界磁场增加. T c 的降低归因于电子比热系数和电声子耦合强度的减小. 此外, 该高熵合金的 T c 对价电子数依赖关系与二元A15超导体和其他结构高熵合金超导体均不同, 且表明可以通过降低价电子数目来进一步提高 T c . 本文不仅揭示了一类新结构类型的高熵合金超导体, 而且提供了高熵合金中依赖于多晶型性超导的首个示例.
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V1.4Nb1.4Mo0.2Al0.5Ga0.5 is an A15-type HEA superconductor with Tc = 10.2 K and a disorder-enhanced μ0Hc2(0) of approximately 20 T, which are the highest recorded values among HEA superconductors under ambient conditions.
“V1.4Nb1.4Mo0.2Al0.5Ga0.5 is an A15-type HEA superconductor with T c = 10.2 K and a disorder-enhanced μ 0Hc2(0) of approximately 20 T, which are the highest recorded values among HEA superconductors under ambient conditions 57 .”
From Recent advances in high-entropy superconductors (2024) · cites this paper as [57]
The μ0Hc2(0) exceeding the Pauli paramagnetic limit was also found in BCC-type ScVTiHfNb, HCP-type Ru0.35Os0.35Mo0.12W0.1Zr0.1, A15-type (Nb0.5V0.5)3-xMoxAl0.5Ga0.5, and α-Mn-type Ru0.35Os0.35Mo0.1W0.1Zr0.1 HEA superconductors.
“The μ 0Hc2(0) exceeding the Pauli paramagnetic limit was also found in BCC-type ScVTiHfNb 21 , HCP-type Ru0.35Os0.35Mo0.12W0.1Zr0.1 89 , A15-type (Nb0.5V0.5)3x Mo x Al0.5Ga0.5 57 , and α -Mn-type Ru0.35Os0.35Mo0.1W0.1Zr0.1 HEA superconductors 89 .”
From Recent advances in high-entropy superconductors (2024) · cites this paper as [57]
Quantifying intrinsic ρN values remains challenging owing to the polycrystalline nature of high-entropy samples, where resistivity is largely influenced by grain boundary contributions.
“However, quantifying the intrinsic ρ N values remains challenging owing to the polycrystalline nature of highentropy samples, where resistivity is largely in fl uenced by grain boundary contributions 57,88 .”
From Recent advances in high-entropy superconductors (2024) · cites this paper as [57]
The Results and Discussion section reports resistivity measurements, grain-size differences, and enhanced normal-state resistivity attributed to strong disorder. It does not say that grain boundaries largely influence resistivity or make intrinsic ρN difficult to quantify. Searches for grain boundaries, polycrystalline samples, and intrinsic resistivity found no passage establishing that explanation; page numbers were unavailable. (LLM, conf=0.74)
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References 45 · Cited by 43
Research works printed but not linked: 4
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- [5]5. Braun HF, Engel N, Parthé E. Polymorphism and super- conductivity of LaIr 2 Si 2 . Phys Rev B, 1983, 28: 1389-1395
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- Authors
- Wu, J., Liu, B., Cui, Y., Zhu, Q., Xiao, G., Wang, H., Wu, S., Cao, G., & Ren, Z.
- Affiliations
- Fudan University (CN)
- Westlake University (CN)
- Hangzhou Normal University (CN)
- Zhejiang University (CN)
- Corresponding author
- Ren, Zhi
- Venue
- Science China Materials
- Published
- 2020-01-10
- Volume
- 63
- Issue
- 5
- Pages
- 823-831
- ISSN
- 2095-8226 (ISSN-L)
- 2199-4501
- OpenAlex
- W2999746809
- Semantic Scholar
- 811f1f5ef767089580df67bd9be9da4dae789d7a
- Cited by
- 43
- References
- 45
- Citations by year
- 2026: 4 · 2025: 8 · 2024: 4 · 2023: 7 · 2022: 7 · 2021: 7 · 2020: 6
- FWCI
- 3.32
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Science China Materials (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- arXiv (Cornell University)
- Topics
- Physical Sciences › Engineering › Mechanical Engineering › High Entropy Alloys Studies
- Physical Sciences › Physics and Astronomy › Condensed Matter Physics › Physics of Superconductivity and Magnetism
- Physical Sciences › Engineering › Biomedical Engineering › Superconducting Materials and Applications
- Keywords
- high-entropy alloys, superconductivity, polymorphism, A15 structure, body-centered cubic lattice, polymorphic transformation, bulk superconductivity, upper critical field, electron-phonon coupling, valence electron count, annealing
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