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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Exploring the $A$-V-Sb landscape beyond $A$$\mathrm{V_3}$ $\mathrm{Sb_5}$: A case study on the $\mathrm{KV_6}$ $\mathrm{Sb_6}$ Kagome compound

Kagome compounds have garnered attention in the past few years for their intriguing magnetic properties arising from spin frustration dictated by the geometry of the Kagome sublattice. In this paper, we highlight the success of the unconventional hydride route for the fast and easy synthesis of the Kagome compound $\mathrm{KV_6}$ $\mathrm{Sb_6}$. Here, high-temperature in situ powder x-ray diffraction (PXRD) studies proved to be useful in hinting at the existence of $\mathrm{KV_6}$ $\mathrm{Sb_6}$, identifying its synthesis conditions, and understanding the reaction mechanism. The crystal structure for $\mathrm{KV_6}$ $\mathrm{Sb_6}$ was determined from high-resolution PXRD data. The compound has a layered structure [$R\overline{3}m, a = 5.5318$ (9) Å, $c = 34.23$ (3)Å 3 $Z = 3$] at room temperature] and features a Kagome bilayer of V atoms. $\mathrm{KV_6}$ $\mathrm{Sb_6}$ is isostructural to the previously reported $\mathrm{RbV_6}$ $\mathrm{Sb_6}$ and $\mathrm{CsV_6}$ $\mathrm{Sb_6}$ compounds. $\mathrm{KV_6}$ $\mathrm{Sb_6}$ is thermally stable in vacuum up to 1173 K, as evident from the high-temperature in situ PXRD and differential scanning calorimetric analysis. Investigation of magnetic properties for $\mathrm{KV_6}$ $\mathrm{Sb_6}$ between 2 and 300 K reveals temperature-independent paramagnetism and an absence of superconductivity, like the Rb and Cs analogs. Furthermore, we compare the magnetic properties of K V 3 Sb 5 , another ternary Kagome compound, synthesized via two different methods: the hydride route and the traditional route from elements. Low-temperature transport property measurements of $\mathrm{KV_6}$ $\mathrm{Sb_6}$ indicate metallic behavior and an intrinsically low thermal conductivity of $\mathrm{1.0 W K^-1}$ $\mathrm{m^-1}$ at 300 K. The layered structure of $\mathrm{KV_6}$ $\mathrm{Sb_6}$ makes it an attractive candidate for deintercalation and doping studies to tune both magnetic and transport properties, laying a foundation for further studies.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reaction pathways and Sb(III) minerals formation during the reduction of Sb(V) by Rhodoferax ferrireducens strain YZ-1

Antimony (Sb), a non-essential metalloid, can be released into the environment through various industrial ac-tivities. Sb(III) is considered more toxic than Sb(V), but Sb(III) can be immobilized through the precipitation of insoluble Sb 2 S 3 or Sb 2 O 3 . In the subsurface, Sb redox chemistry is largely controlled by microorganisms; how-ever, the exact mechanisms of Sb(V) reduction to Sb(III) are still unclear. Here, in this study, a new strain of Sb(V)-reducing bacterium, designated as strain YZ-1, that can respire Sb(V) as a terminal electron acceptor was iso-lated from Sb-contaminated soils. 16S-rRNA gene sequencing of YZ-1 revealed high similarity to a known Fe(III)-reducer, Rhodoferax ferrireducens. XRD and XAFS analyses revealed that bioreduction of Sb(V) to Sb(III) proceed through a transition from amorphous valentinite to crystalline senarmontite (allotropes of Sb 2 O 3 ). Genomic DNA sequencing found that YZ-1 possesses arsenic (As) metabolism genes, including As(V) reductase arsC. The qPCR analysis showed that arsC was highly expressed during Sb(V)-reduction by YZ-1, and thus is proposed as the potential Sb(V) reductase in YZ-1. This study provides new insight into the pathways and products of microbial Sb(V) reduction and demonstrates the potential of a newly isolated bacterium for Sb bioremediation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Synthesis, crystal and electronic structure of the Zintl phase Ba 16 Sb 11 . A case study uncovering greater structural complexity via monoclinic distortion of the tetragonal Ca 16 Sb 11 structure type

The binary Zintl phase Ba 16 Sb 11 has been synthesized and structurally characterized. Detailed studies via single-crystal X-ray diffraction methods indicate that although Ba 16 Sb 11 appears to crystallize in the tetragonal Ca 16 Sb 11 structure type (space group $P\bar{4}2_1$m with a=13.5647(9) Å, c=12.4124(12)Å, Z=2, R 1 = 3.14%; wR 2 = 4.77%), there exists an extensive structural disorder. Some Ba 16 Sb 11 crystals were found to be monoclinic and the structure was solved and refined in space group P2 1 (a=18.3929(12) Å, b=13.5233(8) Å, c=18.3978(12) Å, β=94.6600(10)°; Z=4, R 1 =5.84 %; wR 2 =9.58 %). The latter corresponds to a 2-fold superstructure of the tetragonal one, which provides a disorder-free structural model. In both descriptions, the disordered tetragonal and the ordered monoclinic superstructure, the basic building units that make up the structure of this Ba-rich compound are pairs of face-shared square antiprisms of Ba atoms, which are centered by Sb atoms. The dimerized antiprisms are linked into parallel chains via square prisms of Ba atoms, which are also centered by Sb atoms. The Zintl concept can be applied in a straightforward manner and as result, the structure of Ba 32 Sb 22 (=2×Ba 16 Sb 11 ) can be rationalized as (Ba 2+ ) 32 (Sb 3– ) 20 [Sb 2 ] 4– . Notably, the partitioning of the valence electrons is done taking into an account the homoatomic Sb–Sb contacts (d=3.01 Å), which can be clearly distinguished in the lower symmetry space group. Electronic structure calculations of Ba 16 Sb 11 are in good accordance with the Zintl rationalization and predict a semiconductor with a band gap of 0.77 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Proximity Magnetism in Mn(Bi,Sb) 2 Te 4 –(Bi,Sb) 2 Te 3 /MnTe Natural Heterostructures

Magnetic topological insulators and their heterostructures provide significant opportunities to couple band topology with a nontrivial spin configuration for enhanced spintronic device performance, as well as designing magnetoelectric systems and functionalities. We find that Mn interdiffusion from MnTe when interfaced with (Bi,Sb) 2 Te 3 stabilizes as self-organized Mn(Bi,Sb) 2 Te 4 septuple lamellae among alternating (Bi,Sb) 2 Te 3 quintuple layers, as observed using scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. We further demonstrate a valuable combination of magnetic and topological orders in these naturally formed Mn(Bi,Sb) 2 Te 4 –(Bi,Sb) 2 Te 3 heterostructures, which are exchange-coupled with MnTe. Magnetotransport experiments and quantum magnetism simulations reveal that, above its own Néel temperature T N ∼ 20 K, Mn(Bi,Sb) 2 Te 4 mediates the exchange field leading to an anomalous Hall effect at the (Bi,Sb) 2 Te 3 /MnTe interface, with an enhanced interfacial T N exceeding 200 K, approaching that of the bulk MnTe. This magnetic interface, in turn, allows a robust and deterministic spin–orbit torque switching without an external magnetic field at a low critical current density of 3 × 10 5 A cm –2 . The antiferromagnetically coupled architecture of Mn(Bi,Sb) 2 Te 4 –(Bi,Sb) 2 Te 3 /MnTe, featuring magnetic and topological proximity effects across a chalcogenide backbone, is rich in fundamental interface physics and holds the potential for practical applications in spintronics.

magnetic topological insulator↗
DOE OSTI2021

Anisotropic Structural Collapse of Mg 3 Sb 2 and Mg 3 Bi 2 at High Pressure

Alloys between Mg 3 Sb 2 and Mg 3 Bi 2 have recently been shown to be exceptional thermoelectric materials due in part to their anomalously low thermal conductivity. In the present study, in situ high-pressure synchrotron X-ray diffraction was used to investigate the structure and bonding in Mg 3 Sb 2 and Mg 3 Bi 2 at pressures up to 50 GPa. Our results confirm prior predictions of isotropic in-plane and out-of-plane compressibility but reveal large disparities between the bond strength of the two distinct Mg sites. Using single-crystal diffraction, we show that the octahedral Mg–Sb bonds are significantly more compressible than the tetrahedral Mg–Sb bonds in Mg 3 Sb 2 , which lends support to prior arguments that the weaker octahedral Mg bonds are responsible for the anomalous thermal properties of Mg 3 Sb 2 and Mg 3 Bi 2 . Further, we report the discovery of a displacive and reversible phase transition in both Mg 3 Sb 2 and Mg 3 Bi 2 above 7.8 and 4.0 GPa, respectively. Furthermore, the transition to the high-pressure structure involves a highly anisotropic volume collapse, in which the out-of-plane axis compresses significantly more than the in-plane axes. Single-crystal diffraction at high pressure was used to solve the monoclinic high-pressure structure ( C 2/ m ), which is a distorted variant of the ambient-pressure structure containing four unique Mg coordination environments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Encapsulated Sb and Sb 2 O 3 particles in waste-tire derived carbon as stable composite anodes for sodium-ion batteries

A conductive network of waste-tire derived carbon (WTC) was used to produce homogeneous Sb/WTC and Sb 2 O 3 /WTC composite materials via ball milling as promising anodes for sodium-ion batteries (SIBs). Highly reversible redox peaks at 0.81/0.71, 0.25 V for Sb/WTC and 0.80/0.76, 0.21/0.26 V for Sb 2 O 3 /WTC anodes have been observed related to Na + intercalation and deintercalation in carbon and Na–Sb and Na 3 Sb as plausible conversion/alloy reactions. Sodium half-cells delivered reversible discharge capacities of 206 mA h g -1 and 207 mA h g -1 at a current density of 37 mA g -1 for the composite Sb/WTC and Sb 2 O 3 /WTC materials, respectively. Both the Sb/WTC and Sb 2 O 3 /WTC composite materials showed impressive capacity retention with 85% and 88%, respectively after 100 cycles. Furthermore, rate capability studies at 60 °C yielded an enhanced capacity of 240 mA h g -1 for Sb/WTC and 300 mA h g -1 for Sb 2 O 3 /WTC at 37 mA g -1 .

25 ENERGY STORAGE↗
DOE OSTI2021

Evolution of magnetic interactions in Sb-substituted MnBi 2 Te 4

The Mn(Bi 1–x Sb x ) 2 Te 4 series is purported to span from an antiferromagnetic (AF) topological insulator at x = 0 to a trivial AF insulator at x = 1. Here we report on neutron diffraction and inelastic neutron scattering studies of the magnetic interactions across this series. All compounds measured possess ferromagnetic (FM) triangular layers and we find a crossover from AF to FM interlayer coupling near x = 1 for our samples. The large spin gap at x = 0 closes rapidly and the average FM exchange interactions within the triangular layer increase with Sb substitution. Similar to a previous study of MnBi 2 Te 4 , we find severe spectral broadening which increases dramatically across the compositional series. In addition to broadening, we observe an additional sharp magnetic excitation in MnSb 2 Te 4 that may indicate the development of local magnetic modes originating from antisite disorder between Mn and Sb sublattices. Here, the results suggest that both substitutional and antisite disorder contribute substantially to the magnetism in Mn(Bi 1–x Sb x ) 2 Te 4 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Synthesis and structural characterization of orthorhombic Cu 3– δ Sb ( δ ≈ 0.1) and hexagonal Cu 3 Sb 1–x In x (x ≈ 0.2) phases

Cu 3 Sb is a known copper-rich phase in the Cu–Sb binary phase diagram. It is reported to be dimorphic, with a low-temperature form adopting the orthorhombic Cu 3 Ti structure type (space group Pmmn , No. 59). The high-temperature form crystallizes in the cubic space group F m 3 - m $Fm‾{3}m$ (No. 225), and is isostructural with BiF 3 . Neither polymorph has been carefully characterized to date, with both structures being assigned to the respective structure type, but never refined. With this study, we provide structural evidence, based on single-crystal and powder X-ray diffraction data that the low-temperature orthorhombic phase exists with a significant amount of defects on one of the Cu-sites. As a result, its composition is not Cu 3 Sb, but rather Cu 3– δ Sb ( δ = 0.13(1)). The cubic form could not be accessed as a part of this study, but another Cu-rich phase, Cu 3 Sb ≈0.8 In ≈0.2 , was also identified. It adopts the hexagonal Ni 3 Sn structure type (space group P 6 3 / mmc , No. 194) and represents an In-substituted variant of a hitherto unknown structural modification of Cu 3 Sb. Whether the latter can exist as a binary phase, or what is the minimum amount of In inclusions needed to stabilize it remains to be determined. Measurements of the thermopower of Cu 3– δ Sb ( δ = 0.13(1)) were conducted in the range of 300–600 K and demonstrated a maximum value of ca. 50 μV/K at 600 K, indicative of a p -type transport mechanism. Electrical resistivity measurements for the same sample confirmed that it exhibits metallic-like behavior, with a room temperature value of 0.43 mΩ cm. Electronic structure calculations show the absence of a band gap. Thermal analysis was utilized to ascertain the congruent melting of both phases.

Crystallography↗
DOE OSTI2022

Synthesis and structural characterization of the new Zintl phases Eu 10 Mn 6 Bi 12 and Yb 10 Zn 6 Sb 12

Two new ternary compounds, Eu 10 Mn 6 Bi 12 and Yb 10 Zn 6 Sb 12 , were synthesized and structurally characterized. The synthesis was achieved either through reactions in sealed niobium tubes or in alumina crucibles by combining the elements in excess molten Sb. Their structures were elucidated using single-crystal X-ray diffraction, and they were determined to crystallize in the orthorhombic space group Cmmm (no. 65) with the Eu 10 Cd 6 Bi 12 structure type. Akin to the archetype phase, both Mn and Zn sites contain about 25% of vacancies. Furthermore, the anionic substructure of the title phases can be described as [M 6 Pn 12 ] (M = Zn, Mn; Pn = Sb, Bi) double layers composed of the corner and edge-sharing [MPn 4 ] tetrahedra, linked by [Pn 2 ] 4– dumbbells. Eu 2+ /Yb 2+ cations fill the space between the layers, with the valence electron counts adhering closely to the Zintl–Klemm rules, i.e., both Eu 10 Mn 6 Bi 12 and Yb 10 Zn 6 Sb 12 are expected to be valence-precise compounds. Analysis of the electronic structure and transport properties of Yb 10 Zn 6 Sb 12 indicate semimetallic behavior with relatively low Seebeck coefficient and resistivity that slightly decreases as a function of temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2023

YbV 3 ⁢Sb 4 and EuV 3 ⁢Sb 4 vanadium-based kagome metals with Yb 2+ and Eu 2+ zigzag chains

Here, in this work, we present Yb⁢V 3 ⁢Sb 4 and Eu⁢V 3 ⁢Sb 4 , two compounds exhibiting slightly distorted vanadium-based kagome nets interleaved with zigzag chains of divalent Yb 2+ and Eu 2+ ions. Single crystal growth methods are reported alongside magnetic, electronic, and heat capacity measurements. Yb⁢V 3⁢ Sb 4 is a nonmagnetic metal with no collective phase transitions observed between 60 mK and 300 K. Conversely, Eu⁢V 3 ⁢Sb 4 is a magnetic kagome metal exhibiting easy-plane ferromagneticlike order below T C =32 K with hints of modulated spin texture under low field. With Yb⁢V 3 ⁢Sb 4 and Eu⁢V 3 ⁢Sb 4 we demonstrate another direction for the discovery and development of vanadium-based kagome metals while incorporating the chemical and magnetic degrees of freedom offered by a rare-earth sublattice.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Third Generation Potentially Bifunctional Trithiol Chelate, Its nat,1XX Sb(III) Complex, and Selective Chelation of Radioantimony ( 119 Sb) from Its Sn Target

The therapeutic potential of the Meitner-Auger- and conversion-electron emitting radionuclide 119 Sb remains unexplored because of the difficulty of incorporating it into biologically targeted compounds. To address this challenge, we report the development of 119 Sb production from electroplated tin cyclotron targets and its complexation by a novel trithiol chelate. Here, the chelation reaction occurs in harsh solvent conditions even in the presence of large quantities of tin, which are necessary for production on small, low energy (16 MeV) cyclotrons. The 119 Sb-trithiol complex has high stability and can be purified by HPLC. The third generation trithiol chelate and the analogous stable nat Sb-trithiol compound were synthesized and characterized, including by single crystal X-ray diffraction analyses.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Tunable unconventional kagome superconductivity in charge ordered RbV 3 Sb 5 and KV 3 Sb 5

Unconventional superconductors often feature competing orders, small super fluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV 3 Sb 5 , key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of super conductivity in RbV 3 Sb 5 and KV 3 Sb 5 . At ambient pressure, we observed time reversal symmetry breaking charge order below ${T}_{1}^{*}$ ≃ 110 K in RbV 3 Sb 5 with an additional transition at ${T}_{2}^{*}$ ≃ 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome super conductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Tuning charge density wave order and superconductivity in the kagome metals KV 3 Sb 5 – x Sn x and RbV 3 Sb 5 – x Sn x

The family of AV 3 Sb 5 (A = K, Rb, Cs) kagome metals exhibits charge density wave (CDW) order, proposed to be chiral, followed by a lower temperature superconducting state. Recent studies have proposed the importance of band structure saddle points proximal to the Fermi energy in governing these two transitions. Here we show the effects of hole doping achieved via chemical substitution of Sn for Sb on the CDW and superconducting states in both KV 3 Sb 5 and RbV 3 Sb 5 and generate a phase diagram. Furthermore, hole doping lifts the Γ pocket and van Hove singularities toward E F causing the superconducting T C in both systems to increase to about 4.5 K, while rapidly suppressing the CDW state.

36 MATERIALS SCIENCE↗
DOE OSTI2021

From Three-Dimensional Clathrates to Two-Dimensional Zintl Phases AMSb 2 (A = Rb, Cs; M = Ga, In) Composed of Pentagonal M–Sb Rings

Three new antimonide Zintl phases, RbGaSb 2 , CsGaSb 2 , and CsInSb 2 , were discovered during exploration of corresponding A–M–Sb (A = Rb, Cs; M = Ga, In) ternary systems while searching for new clathrates. The AGaSb 2 phases crystallize in the tetragonal space group P4 2 /nmc (No. 137) in the LiBS 2 structure type, while CsInSb 2 crystallizes in lower symmetry in the orthorhombic space group Cmce (No. 64) in the KGaSb 2 structure type with additional disorder of one of the Cs sites. The crystal structures of all three reported AMSb 2 compounds are composed of two-dimensional [MSb 2 ] – tetrahedral layers separated by Rb + or Cs + cations. [MSb 2 ] – layers are built from fused M–Sb pentagons and hexagons, which are also the main structural units for A 8 M 27 Sb 19 clathrate cages. The semiconductor nature of AMSb 2 was suggested by band structure calculations and confirmed by transport property characterization. CsGaSb 2 is a rare example of an n-type pnictide Zintl phase. Finally, all reported compounds exhibit low thermal conductivity typical for complex antimonides of heavy elements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗