Materials

Research

13 pages, 3063 KiB

Open AccessArticle

Thermal Expansion and Rattling Behavior of Gd-Filled Co₄Sb₁₂ Skutterudite Determined by High-Resolution Synchrotron X-ray Diffraction

by João E. F. S. Rodrigues, Javier Gainza, Federico Serrano-Sánchez, Romualdo S. Silva, Jr., Catherine Dejoie, Norbert M. Nemes, Oscar J. Dura, José L. Martínez and José Antonio Alonso

Materials 2023, 16(1), 370; https://doi.org/10.3390/ma16010370 - 30 Dec 2022

Cited by 3 | Viewed by 1041

Abstract

In this work, Gd-filled skutterudite Gd_xCo₄Sb₁₂ was prepared using one step method under high pressure in a piston-cylinder-based press at 3.5 GPa and moderate temperature of 800 °C. A detailed structural characterization was performed using synchrotron X-ray diffraction [...] Read more.

In this work, Gd-filled skutterudite Gd_xCo₄Sb₁₂ was prepared using one step method under high pressure in a piston-cylinder-based press at 3.5 GPa and moderate temperature of 800 °C. A detailed structural characterization was performed using synchrotron X-ray diffraction (SXRD), revealing a filling fraction of x = 0.033(2) and an average <Gd–Sb> bond length of 3.3499(3) Å. The lattice thermal expansion accessed via temperature-dependent SXRD led to a precise determination of a Debye temperature of 322(3) K, from the fitting of the unit-cell volume expansion using the second order Grüneisen approximation. This parameter, when evaluated through the mean square displacements of Co and Sb, displayed a value of 265(2) K, meaning that the application of the harmonic Debye theory underestimates the Debye temperature in skutterudites. Regarding the Gd atom, its intrinsic disorder value was ~5× and ~25× higher than those of the Co and Sb, respectively, denoting that Gd has a strong rattling behavior with an Einstein temperature of

θ_{E}

= 67(2) K. As a result, an ultra-low thermal conductivity of 0.89 W/m·K at 773 K was obtained, leading to a thermoelectric efficiency zT of 0.5 at 673 K. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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10 pages, 4109 KiB

Open AccessArticle

Pressure-Tuning Superconductivity in Noncentrosymmetric Topological Materials ZrRuAs

by Changhua Li, Yunlong Su, Cuiwei Zhang, Cuiying Pei, Weizheng Cao, Qi Wang, Yi Zhao, Lingling Gao, Shihao Zhu, Mingxin Zhang, Yulin Chen, Youguo Shi, Gang Li and Yanpeng Qi

Materials 2022, 15(21), 7694; https://doi.org/10.3390/ma15217694 - 01 Nov 2022

Cited by 1 | Viewed by 1338

Abstract

Recently, the hexagonal phase of ternary transition metal pnictides TT’X (T = Zr, Hf; T’ = Ru; X = P, As), which are well-known noncentrosymmetric superconductors, were predicted to host nontrivial bulk topology. In this work, we systematically investigate the electronic responses of [...] Read more.

Recently, the hexagonal phase of ternary transition metal pnictides TT’X (T = Zr, Hf; T’ = Ru; X = P, As), which are well-known noncentrosymmetric superconductors, were predicted to host nontrivial bulk topology. In this work, we systematically investigate the electronic responses of ZrRuAs to external pressure. At ambient pressure, ZrRuAs show superconductivity with T_c ~ 7.74 K, while a large upper critical field ~ 13.03 T is obtained for ZrRuAs, which is comparable to the weak-coupling Pauli limit. The resistivity of ZrRuAs exhibits a non-monotonic evolution with increasing pressure. The superconducting transition temperature T_c increases with applied pressure and reaches a maximum value of 7.93 K at 2.1 GPa, followed by a decrease. The nontrivial topology is robust and persists up to the high-pressure regime. Considering both robust superconductivity and intriguing topology in this material, our results could contribute to studies of the interplay between topological electronic states and superconductivity. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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8 pages, 2708 KiB

Open AccessArticle

Crystal Structures and Electronic Properties of BaAu Compound under High Pressure

by Bingtan Li, Jianyun Wang, Shuai Sun and Hanyu Liu

Materials 2022, 15(20), 7381; https://doi.org/10.3390/ma15207381 - 21 Oct 2022

Viewed by 1025

Abstract

The investigations of Au-bearing alloy materials have been of broad research interest as their relevant features exhibit significant advantages compared with pure Au. Here, we extensively investigate the compression behaviors of BaAu compounds via first-principles calculations and find that a high-pressure cubic phase [...] Read more.

The investigations of Au-bearing alloy materials have been of broad research interest as their relevant features exhibit significant advantages compared with pure Au. Here, we extensively investigate the compression behaviors of BaAu compounds via first-principles calculations and find that a high-pressure cubic phase is calculated to be stable above 12 GPa. Further electronic calculations indicate that despite the low electronegativity of Ba, Fd-3m-structured BaAu exhibits metallic characteristics, which is different from those of semiconducting alkali metal aurides that possess slight characteristics of an ionic compound. These findings provide a step toward a further understanding of the electronic properties of BaAu compounds and provide key insight for exploring the other Au-bearing alloy materials under extreme conditions. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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11 pages, 1712 KiB

Open AccessEditor’s ChoiceArticle

Destabilization of the Charge Density Wave and the Absence of Superconductivity in ScV₆Sn₆ under High Pressures up to 11 GPa

by Xiaoxiao Zhang, Jun Hou, Wei Xia, Zhian Xu, Pengtao Yang, Anqi Wang, Ziyi Liu, Jie Shen, Hua Zhang, Xiaoli Dong, Yoshiya Uwatoko, Jianping Sun, Bosen Wang, Yanfeng Guo and Jinguang Cheng

Materials 2022, 15(20), 7372; https://doi.org/10.3390/ma15207372 - 21 Oct 2022

Cited by 20 | Viewed by 3217

Abstract

RV₆Sn₆ (R = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as AV₃Sb₅ (A = K, Rb, Cs) compounds. Unlike AV [...] Read more.

RV₆Sn₆ (R = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as AV₃Sb₅ (A = K, Rb, Cs) compounds. Unlike AV₃Sb₅, ScV₆Sn₆ is the only compound among the series of RV₆Sn₆ that displays a charge density wave (CDW) order at ambient pressure, yet it shows no superconductivity (SC) at low temperatures. Here, we perform a high-pressure transport study on the ScV₆Sn₆ single crystal to track the evolutions of the CDW transition and to explore possible SC. In contrast to AV₃Sb₅ compounds, the CDW order of ScV₆Sn₆ can be suppressed completely by a pressure of about 2.4 GPa, but no SC is detected down to 40 mK at 2.35 GPa and 1.5 K up to 11 GPa. Moreover, we observed that the resistivity anomaly around the CDW transition undergoes an obvious change at ~2.04 GPa before it vanishes completely. The present work highlights a distinct relationship between CDW and SC in ScV₆Sn₆ in comparison with the well-studied AV₃Sb₅. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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10 pages, 2026 KiB

Open AccessEditor’s ChoiceArticle

Pressure-Induced Superconductivity of the Quasi-One-Dimensional Organic Conductor (TMTTF)₂TaF₆

by Miho Itoi, Toshikazu Nakamura and Yoshiya Uwatoko

Materials 2022, 15(13), 4638; https://doi.org/10.3390/ma15134638 - 01 Jul 2022

Cited by 2 | Viewed by 1682

Abstract

We investigated the superconductivity of (TMTTF)₂TaF₆ (TMTTF: tetramethyl-tetrathiafulvalene) by conducting resistivity measurements under high pressure up to 8 GPa. A cubic anvil cell (CAC) pressure generator, which can produce hydrostatic high-pressure, was used for this study. Since the generalized temperature-pressure [...] Read more.

We investigated the superconductivity of (TMTTF)₂TaF₆ (TMTTF: tetramethyl-tetrathiafulvalene) by conducting resistivity measurements under high pressure up to 8 GPa. A cubic anvil cell (CAC) pressure generator, which can produce hydrostatic high-pressure, was used for this study. Since the generalized temperature-pressure (T-P) diagram of (TMTCF)₂X (C = Se, S, X: monovalent anion) based on (TMTTF)₂PF₆ (T_CO = 70 K and spin-Peierls: SP, T_SP = 15 K) was proposed by Jérome, exploring superconductivity states using high-pressure measurement beyond 4 GPa has been required to confirm the universality of the electron-correlation variation under pressure in (TMTTF)₂X (TMTTF)₂TaF₆, which has the largest octahedral-symmetry counter anion TaF₆ in the (TMTTF)₂X series, possesses the highest charge-ordering (CO) transition temperature (T_CO = 175 K) in (TMTTF)₂X and demonstrates an anti-ferromagnetic transition (T_AF = 9 K) at ambient pressure. A superconducting state in (TMTTF)₂TaF₆ emerged after a metal-insulator transition was suppressed with increasing external pressure. We discovered a superconducting state in 5 ≤ P ≤ 6 GPa from T_c = 2.1 K to 2.8 K, whose pressure range is one-third narrower than that of X = SbF₆ (5.4 ≤ P ≤ 9 GPa). In addition, when the pressures with maximum SC temperatures are compared between the PF₆ and the TaF₆ salts, we found that (TMTTF)₂TaF₆ has a 0.75 GPa on the negative pressure side in the T-P phase diagram of (TMTTF)₂PF₆. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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10 pages, 2611 KiB

Open AccessCommunication

Structure Determination, Mechanical Properties, Thermal Stability of Co₂MoB₄ and Fe₂MoB₄

by Shijing Zhao, Wenju Zhou, Xiaojun Xiang, Xuyan Cao, Ning Chen, Weifeng Chen, Xiaohui Yu, Bingmin Yan and Huiyang Gou

Materials 2022, 15(9), 3031; https://doi.org/10.3390/ma15093031 - 21 Apr 2022

Viewed by 1432

Abstract

The precise determination of atomic position of materials is critical for understanding the relationship between structure and properties, especially for compounds with light elements of boron and single or multiple transition metals. In this work, the single crystal X-ray diffraction is employed to [...] Read more.

The precise determination of atomic position of materials is critical for understanding the relationship between structure and properties, especially for compounds with light elements of boron and single or multiple transition metals. In this work, the single crystal X-ray diffraction is employed to analyze the atomic positions of Co₂MoB₄ and Fe₂MoB₄ with a Ta₃B₄-type structure, and it is found that the lengths of B-B bonds connecting the two zig-zag boron chains are 1.86 Å and 1.87 Å, but previously unreported 1.4 Å. Co and Fe atoms occupy the same crystallographic position in lattice for the doped samples and the valence is close to the metal itself, and Co/Fe K-edge X-ray Absorption Fine Structure(XAFS) spectra of borides with different ratios of Co to Fe are collected to detect the local environment and chemical valence of Co and Fe. Vickers hardness and nano indentation measurements are performed, together with the Density Functional Theory (DFT) calculations. Finally, Co₂MoB₄ possess better thermal stability than Fe₂MoB₄ evaluated by Thermogravimetric Differential Thermal Analysis (TG-DTA) results. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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13 pages, 4334 KiB

Open AccessEditor’s ChoiceArticle

Pressure-Induced Superconductivity in Iron-Based Spin-Ladder Compound BaFe_2+δ(S_1−xSe_x)₃

by Hiroki Takahashi, Ryosuke Kikuchi, Chizuru Kawashima, Satoshi Imaizumi, Takuya Aoyama and Kenya Ohgushi

Materials 2022, 15(4), 1401; https://doi.org/10.3390/ma15041401 - 14 Feb 2022

Cited by 2 | Viewed by 2037

Abstract

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted [...] Read more.

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted much attention as a platform for studying the interplay between magnetic and orbital ordering. In these compounds, BaFe₂S₃ and BaFe₂Se₃ were found to exhibit superconductivity under high pressure, having a different crystal and magnetic structure at low temperature. We report a brief review of the iron-based spin-ladder compound and recent studies for BaFe_2+δ(S_1−xSe_x)₃. BaFe₂(S_0.75 Se_0.25)₃ is in the vicinity of the boundary of two different magnetic phases and it is intriguing to perform high pressure experiments for studying superconductivity, since effects of large magnetic fluctuations on superconductivity are expected. The effect of iron stoichiometry on the interplay between magnetism and superconductivity is also studied by changing the iron concentration in BaFe_2+δSe₃. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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10 pages, 4220 KiB

Open AccessArticle

Investigations of Structural, Electronic and Magnetic Properties of MnSe under High Pressure

by Jing Zhao, Hanxing Zhang, Caoping Niu and Xianlong Wang

Materials 2022, 15(3), 1109; https://doi.org/10.3390/ma15031109 - 31 Jan 2022

Viewed by 2372

Abstract

Properties of pressurized MnSe were investigated based on the first-principles methods using exchange–correlation functionals of the local density approximation (generalized gradient approximation) with and without the Hubbard U correction. Our results show that the Hubbard U (U = 4 eV) correction is necessary [...] Read more.

Properties of pressurized MnSe were investigated based on the first-principles methods using exchange–correlation functionals of the local density approximation (generalized gradient approximation) with and without the Hubbard U correction. Our results show that the Hubbard U (U = 4 eV) correction is necessary to correctly describe the phase transition behaviors of MnSe. We found that at the static condition, phase transitions from the low-temperature phase with a NiAs-type structure (P6₃/mmc) to the P4/nmm phase at 50.5 GPa and further to the Pnma phase at 81 GPa are observed. However, if the transition starts from the room-temperature phase with a NaCl-type structure (Fm-3m), the transition-sequences and -pressures will be different, indicating that temperature can strongly affect the phase transition behaviors of MnSe. Furthermore, we found that pressure-induced negative charge transfer will promote spin crossover. The calculated superconducting properties of the Pnma phase indicate that it may be an unconventional superconductor. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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8 pages, 2314 KiB

Open AccessArticle

High-Pressure Structures and Superconductivity of Barium Iodide

by Shubo Wei and Hanyu Liu

Materials 2022, 15(2), 522; https://doi.org/10.3390/ma15020522 - 10 Jan 2022

Cited by 1 | Viewed by 1724

Abstract

Generally, pressure is a useful tool to modify the behavior of physical properties of materials due to the change in distance between atoms or molecules in the lattice. Barium iodide (BaI₂), as one of the simplest and most prototypical iodine compounds, [...] Read more.

Generally, pressure is a useful tool to modify the behavior of physical properties of materials due to the change in distance between atoms or molecules in the lattice. Barium iodide (BaI₂), as one of the simplest and most prototypical iodine compounds, has substantial high pressure investigation value. In this work, we explored the crystal structures of BaI₂ at a wide pressure range of 0–200 GPa using a global structure search methodology. A thermodynamical structure with tetragonal I4/mmm symmetry of BaI₂ was predicted to be stable at 17.1 GPa. Further electronic calculations indicated that I4/mmm BaI₂ exhibits the metallic feature via an indirect band gap closure under moderate pressure. We also found that the superconductivity of BaI₂ at 30 GPa is much lower than that of CsI at 180 GPa based on our electron–phonon coupling simulations. Our current simulations provide a step toward the further understanding of the high-pressure behavior of iodine compounds at extreme conditions. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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