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At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on BiTeIr by Materials Project

IrBiTe is Spinel-like structured and crystallizes in the cubic P2_13 space group. The structure is three-dimensional. Ir is bonded to three equivalent Bi and three equivalent Te atoms to form IrBi3Te3 octahedra that share corners with twelve equivalent IrBi3Te3 octahedra, corners with three equivalent BiTeIr3 trigonal pyramids, and corners with three equivalent TeBiIr3 trigonal pyramids. The corner-sharing octahedra tilt angles range from 62–63°. All Ir–Bi bond lengths are 2.77 Å. All Ir–Te bond lengths are 2.70 Å. Bi is bonded to three equivalent Ir and one Te atom to form distorted BiTeIr3 trigonal pyramids that share corners with three equivalent IrBi3Te3 octahedra, corners with six equivalent BiTeIr3 trigonal pyramids, and corners with nine equivalent TeBiIr3 trigonal pyramids. The corner-sharing octahedral tilt angles are 81°. The Bi–Te bond length is 2.95 Å. Te is bonded to three equivalent Ir and one Bi atom to form distorted TeBiIr3 trigonal pyramids that share corners with three equivalent IrBi3Te3 octahedra, corners with six equivalent TeBiIr3 trigonal pyramids, and corners with nine equivalent BiTeIr3 trigonal pyramids. The corner-sharing octahedral tilt angles are 81°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc6Te2Ir by Materials Project

Sc6IrTe2 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Sc sites. In the first Sc site, Sc is bonded in a 4-coordinate geometry to two equivalent Ir and two equivalent Te atoms. Both Sc–Ir bond lengths are 2.69 Å. Both Sc–Te bond lengths are 3.02 Å. In the second Sc site, Sc is bonded in a 5-coordinate geometry to one Ir and four equivalent Te atoms. The Sc–Ir bond length is 3.01 Å. All Sc–Te bond lengths are 3.09 Å. Ir is bonded in a 9-coordinate geometry to nine Sc atoms. Te is bonded in a 9-coordinate geometry to nine Sc atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg5Te by Materials Project

Mg5Te crystallizes in the trigonal R32 space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to ten Mg and two equivalent Te atoms to form distorted MgMg10Te2 cuboctahedra that share corners with eighteen equivalent MgMg10Te2 cuboctahedra, edges with four equivalent TeMg12 cuboctahedra, edges with six equivalent MgMg10Te2 cuboctahedra, faces with four equivalent TeMg12 cuboctahedra, and faces with eight equivalent MgMg10Te2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.19–3.27 Å. Both Mg–Te bond lengths are 3.23 Å. In the second Mg site, Mg is bonded in a distorted trigonal planar geometry to six equivalent Mg and three equivalent Te atoms. All Mg–Te bond lengths are 3.22 Å. Te is bonded to twelve Mg atoms to form TeMg12 cuboctahedra that share corners with six equivalent TeMg12 cuboctahedra, edges with six equivalent TeMg12 cuboctahedra, edges with twelve equivalent MgMg10Te2 cuboctahedra, and faces with twelve equivalent MgMg10Te2 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te6RuBr8 by Materials Project

RuTeTe5Br8 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four ruthenium molecules, four tellurium molecules, and four Te5Br8 clusters. In each Te5Br8 cluster, there are five inequivalent Te1+ sites. In the first Te1+ site, Te1+ is bonded in a single-bond geometry to one Br1- atom. The Te–Br bond length is 3.16 Å. In the second Te1+ site, Te1+ is bonded in a single-bond geometry to one Br1- atom. The Te–Br bond length is 3.04 Å. In the third Te1+ site, Te1+ is bonded in a rectangular see-saw-like geometry to four Br1- atoms. There are a spread of Te–Br bond distances ranging from 2.59–3.05 Å. In the fourth Te1+ site, Te1+ is bonded in a distorted rectangular see-saw-like geometry to four Br1- atoms. There are a spread of Te–Br bond distances ranging from 2.56–3.34 Å. In the fifth Te1+ site, Te1+ is bonded in a T-shaped geometry to three Br1- atoms. There are a spread of Te–Br bond distances ranging from 2.59–2.78 Å. There are eight inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a single-bond geometry to one Te1+ atom. In the second Br1- site, Br1- is bonded in an L-shaped geometry to two Te1+ atoms. In the third Br1- site, Br1- is bonded in a single-bond geometry to one Te1+ atom. In the fourth Br1- site, Br1- is bonded in a distorted L-shaped geometry to two Te1+ atoms. In the fifth Br1- site, Br1- is bonded in a distorted single-bond geometry to two Te1+ atoms. In the sixth Br1- site, Br1- is bonded in a single-bond geometry to one Te1+ atom. In the seventh Br1- site, Br1- is bonded in a 2-coordinate geometry to two Te1+ atoms. In the eighth Br1- site, Br1- is bonded in a 2-coordinate geometry to two Te1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiCa2TeO6 by Materials Project

LiCa2TeO6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li is bonded to six O atoms to form LiO6 octahedra that share corners with six equivalent TeO6 octahedra. The corner-sharing octahedra tilt angles range from 30–33°. There are a spread of Li–O bond distances ranging from 2.11–2.21 Å. Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.39–2.84 Å. Te is bonded to six O atoms to form TeO6 octahedra that share corners with six equivalent LiO6 octahedra. The corner-sharing octahedra tilt angles range from 30–33°. There is two shorter (1.94 Å) and four longer (1.95 Å) Te–O bond length. There are three inequivalent O sites. In the first O site, O is bonded in a 5-coordinate geometry to one Li, three equivalent Ca, and one Te atom. In the second O site, O is bonded to one Li, two equivalent Ca, and one Te atom to form distorted corner-sharing OLiCa2Te tetrahedra. In the third O site, O is bonded in a 5-coordinate geometry to one Li, three equivalent Ca, and one Te atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce2TeMo6(H6O7)6 by Materials Project

Ce2Mo6Te(H14O19)2(H2O)4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of four water molecules and one Ce2Mo6Te(H14O19)2 framework. In the Ce2Mo6Te(H14O19)2 framework, Ce is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Ce–O bond distances ranging from 2.42–2.73 Å. There are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.35 Å. In the second Mo site, Mo is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.33 Å. In the third Mo site, Mo is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.34 Å. There are fourteen inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the second H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.71 Å) H–O bond length. In the third H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.97 Å. In the fourth H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.71 Å) H–O bond length. In the fifth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the sixth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the seventh H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the eighth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the ninth H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (0.99 Å) and one longer (1.73 Å) H–O bond length. In the tenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the eleventh H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the twelfth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the thirteenth H site, H is bonded in a distorted single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.68 Å) H–O bond length. In the fourteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. Te is bonded in an octahedral geometry to six O atoms. There are a spread of Te–O bond distances ranging from 1.93–1.98 Å. There are nineteen inequivalent O sites. In the first O site, O is bonded in a 1-coordinate geometry to two Mo and one Te atom. In the second O site, O is bonded in a 4-coordinate geometry to two Mo, one H, and one Te atom. In the third O site, O is bonded in a distorted trigonal planar geometry to two Mo and one H atom. In the fourth O site, O is bonded in a single-bond geometry to one Mo atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to two Mo atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Ce and one Mo atom. In the seventh O site, O is bonded to two Mo, one H, and one Te atom to form distorted corner-sharing OTeMo2H trigonal pyramids. In the eighth O site, O is bonded in a distorted trigonal planar geometry to two Mo and one H atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Ce and one Mo atom. In the tenth O site, O is bonded in a single-bond geometry to one Mo atom. In the eleventh O site, O is bonded in a single-bond geometry to one Mo atom. In the twelfth O site, O is bonded in a bent 150 degrees geometry to one Ce and one Mo atom. In the thirteenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the fourteenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the fifteenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the sixteenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the seventeenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the eighteenth O site, O is bonded in a water-like geometry to one Ce and two H atoms. In the nineteenth O site, O is bonded in a water-like geometry to two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A Holistic Stabilization of the Anode in Lithium‐Sulfur Batteries Through a Ternary Alloy Fusion

The anode in lithium–sulfur batteries (LSBs) is plagued by not only inhomogeneous lithium (Li) deposition, but also by parasitic side-reactions. Often, a thick anode (∼400 µm) is used to compensate for these drawbacks, lowering gravimetric and volumetric energy densities. In this work, we demonstrate a ternary alloy anode fabricated via scalable thermal fusion of Li with aluminum (Al) and tellurium (Te) to cohesively address these issues. The Al–Li skeleton serves to homogenize Li deposition as well as reinforce the anode, allowing it to be rolled down to low thicknesses. Te incorporation suppresses the reaction of Li with polysulfides (Li 2 Sn) to form lithium sulfide (Li 2 S) and electrolyte degradation. It can also facilitate the formation of polytellurosulfides (Li 2 Te x Sy), which are far more conducive to Li + -ion diffusion. Even under a lean electrolyte/sulfur (E/S) ratio of 8 µL mg −1 and a low negative/positive (N/P) ratio of 3, capacities over 900 mA h g −1 at a C/5 rate are obtained in cells with Li–Te–Al anodes with a capacity retention of 80% after 70 cycles. In comparison, the baseline lithium-metal anode retains only 35% after 50 cycles. Furthermore, the Li–Te–Al anodes confer a 24% boost to gravimetric energy density at the pouch cell level.

25 ENERGY STORAGE↗
DOE OSTI2022

Large Magnetic Gap in a Designer Ferromagnet–Topological Insulator–Ferromagnet Heterostructure

Abstract Combining magnetism and nontrivial band topology gives rise to quantum anomalous Hall (QAH) insulators and exotic quantum phases such as the QAH effect where current flows without dissipation along quantized edge states. Inducing magnetic order in topological insulators via proximity to a magnetic material offers a promising pathway toward achieving the QAH effect at a high temperature for lossless transport applications. One promising architecture involves a sandwich structure comprising two single‐septuple layers (1SL) of MnBi 2 Te 4 (a 2D ferromagnetic insulator) with ultrathin few quintuple layer (QL) Bi 2 Te 3 in the middle, and it is predicted to yield a robust QAH insulator phase with a large bandgap greater than 50 meV. Here, the growth of a 1SL MnBi 2 Te 4 /4QL Bi 2 Te 3 /1SL MnBi 2 Te 4 heterostructure via molecular beam epitaxy is demonstrated and the electronic structure probed using angle‐resolved photoelectron spectroscopy. Strong hexagonally warped massive Dirac fermions and a bandgap of 75 ± 15 meV are observed. The magnetic origin of the gap is confirmed by the observation of the exchange‐Rashba effect, as well as the vanishing bandgap above the Curie temperature, in agreement with density functional theory calculations. These findings provide insights into magnetic proximity effects in topological insulators and reveal a promising platform for realizing the QAH effect at elevated temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Weak Electron–Phonon Coupling and Enhanced Thermoelectric Performance in n-type PbTe–Cu 2 Se via Dynamic Phase Conversion

This study investigates Ga-doped n-type PbTe thermoelectric materials and the dynamic phase conversion process of the second phases via Cu 2 Se alloying. Introducing Cu 2 Se enhances its electrical transport properties while reducing its lattice thermal conductivity (κlat) via weak electron–phonon coupling. Additionally, Cu 2 Te and CuGa(Te/Se) 2 (tetragonal phase) nanocrystals precipitate during the alloying process, resulting in Te vacancies and interstitial Cu in the PbTe matrix. At room temperature, Te vacancies and interstitial Cu atoms serve as n-type dopants, increasing the carrier concentration and electrical conductivity from ≈1.18 × 10 19 cm –3 and ≈1870 S cm –1 to ≈2.26 × 10 19 cm –3 and ≈3029 S cm –1 , respectively. With increasing temperature, the sample exhibits a dynamic change in Cu 2 Te content and the generation of a new phase of CuGa(Te/Se) 2 (cubic phase), strengthening the phonon scattering and obtaining an ultralow k lat . Pb 0.975 Ga 0.025 Te-3%CuSe exhibits a maximum figure of merit of ≈1.63 at 823 K, making it promising for intermediate-temperature device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Intermetallics Based on Sodium Chalcogenides Promote Stable Electrodeposition–Electrodissolution of Sodium Metal Anodes

Sodiophilic micro-composite films of sodium-chalcogenide intermetallics (Na 2 Te and Na 2 S) and Cu particles are fabricated onto commercial copper foam current collectors (Na 2 Te@CF and Na 2 S@CF). For the first time a controllable capacity thermal infusion process is demonstrated. Enhanced wetting by the metal electrodeposition leads to state-of-the-art electrochemical performance. For example, Na 2 Te@CF-based half-cells demonstrate stable cycling at 6 mA cm -2 and 6 mAh cm -2 , corresponding to 54 µm of Na electrodeposited/electrodissolved by geometric area. Sodium metal batteries with Na 3 V 2 (PO 4 ) 3 cathodes are stable at 30C (7 mA cm -2 ) and for 10 000 cycles at 5C and 10C. Cross-sectional cryogenic focused ion beam (cryo-FIB) microscopy details deposited and remnant dissolved microstructures. Sodium metal electrodeposition onto Na 2 Te@CF is dense, smooth, and free of dendrites or pores. On unmodified copper foam, sodium grows in a filament-like manner, not requiring cycling to achieve this geometry. Substrate–metal interaction critically affects the metal–electrolyte interface, namely the thickness and morphology of the solid electrolyte interphase. Density functional theory and mesoscale simulations provide insight into support-adatom energetics, nucleation response, and early-stage morphological evolution. On Na 2 Te sodium atomic dispersion is thermodynamically more stable than isolated clusters, leading to conformal adatom coverage of the surface.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Study of the Effect of Reflections on High-Power, 110-GHz Pulsed Gyrotron Operation

The effect of reflection is studied experimentally and theoretically on a high-power 110-GHz gyrotron operating in the TE 22,6 mode in 3 μs pulses at 96 kV, 40 A. The experimental setup allows variation of the reflected power from 0 to 33% over a range of gyrotron operating conditions. The phase of the reflection is varied by translating the reflector along the axis. Operating at a higher efficiency point, at 4.40 T with 940kW of output power, reflected power exceeding 11% causes a switch from operation in the TE 22,6 to simultaneous operation in the TE 22,6 and TE 21,6 modes with a large decrease of the total gyrotron output power. This switching effect is in good agreement with simulations using the MAGY code. Operating at a more stable point, 4.44 T with 580kW of output power, when the reflection is increased, the output power remains in the TE 22,6 mode but it decreases monotonically with increasing reflection, dropping to 200kW at 33% reflection. Furthermore, at a reflection above 22%, a power modulation at 25 to 30MHz is observed, independent of the phase of the reflected wave. Such a modulated signal may be useful in spectroscopic and other applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Effect of tellurium concentration on the corrosion and mechanical properties of 304 stainless steel in molten FLiNaK salt

In this study, the effect of Te concentration in molten FLiNaK salt on the corrosion and mechanical properties of 304 stainless steel was investigated. The corrosion depth of samples after the immersion tests for 48 h at 600 °C decreased with increasing Te concentration. Likewise, the sample after the immersion test containing 1.0 wt% of Te (1.0 wt% Te sample) showed less reduction in mechanical properties than the 0.1 wt% Te sample. We hypothesize that the condition for a Cr-oxide layer that has the protective property is fulfilled underneath the Ni-Fe rich layer which is formed by the selective leaching of Cr.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Cost-Performance Trade-off in thermoelectric air conditioning system with graded and constant material properties

Thermoelectric (TE) air cooling is a solid-state technology that has the potential to replace conventional vapor compression-based air conditioning. In this paper, we present a detailed system-level modeling for thermoelectric air conditioning system with position-dependent (graded) and constant material properties. Strategies for design optimization of the system are provided in terms of cost-performance trade-off. Realistic convection heat transfer at both sides of the system are taken into account in our modeling. Here, the effects of convection heat transfer coefficients, air flowrate, and thermoelectric material properties are investigated with varying key parameters such as TE leg thickness, module fill factor, and input current. Both constant material properties and graded properties are considered for the TE materials, and they are compared in terms of the degree of cooling, coefficient of performance (COP), and power consumption. For graded materials, we employ one-dimensional finite element methods to solve the coupled electrical and thermal current equations with arbitrary profile of material properties varying with position along the TE legs. We find that graded materials can enhance the degree of cooling, but only at the expense of COP, compared to the case of constant property materials. With constant material properties of ZT = 1 and relatively low electric current, the power consumption of TE coolers can be lower than those of conventional air conditioners at an equivalent cooling capacity. Considering additional advantages such as demand-flexible operation, low noise, and high scalability, thermoelectric cooling could be a competitive technology for future air conditioning applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Computational design of passivants for CdTe grain boundaries

CdTe is the second most-widely deployed photovoltaic (PV) material due to its high efficiency and low manufacturing costs. Currently, polycrystalline CdTe (poly-CdTe) has a record efficiency of similar to 22%, which is still well below the theoretical limit (similar to 30%). Polycrystalline CdTe films that have incorporated Cl or Se show higher efficiency, possibly due to the segregation of these ions to the grain boundaries (GBs), where they may passivate the dangling bonds. However, the efficiency enhancement mechanisms of passivants in CdTe GBs, and the feasibility of employing alternative passivants, have not been well explored. Here, we present a systematic computational study of CdTe GBs with potential passivants, namely S, P, As, Se, and Sb on Te sites, and Na, Mg, Al, Sc, Cu, and Zn on Cd sites. Density functional theory (DFT) calculations were performed on GB dislocation core structures derived from scanning transmission electron microscopy (STEM) images of a model GB (bicrystal). We computed the segregation thermodynamics, electronic density of states, and charge variations near doped CdTe GBs. We find that segregation of impurities to GBs is thermodynamically favorable. For a Te-terminated core, Se, S, and P on Te sites effectively reduce midgap states. For both Cd-and Te-terminated dislocation cores, Sc and Al reduce midgap states when substituted for Cd atoms. Overall, the greatest improvement was achieved with co-doping, i.e. simultaneously substituting Te with Se and substituting Cd with Cu or Al. The elimination of midgap states is predicted to increase the photovoltaic efficiency of CdTe by reducing the recombination at grain boundaries.

14 SOLAR ENERGY↗
DOE OSTI2021

Bulk Glassy GeTe 2 : A Missing Member of the Tetrahedral GeX 2 Family and a Precursor for the Next Generation of Phase-Change Materials

Vitreous germanium disulfide GeS 2 and diselenide GeSe 2 belong to canonical chalcogenide glasses extensively studied over the past half century. Their high-temperature orthorhombic polymorphs are congruently melting compounds, and the tetrahedral crystal and glass structure is largely preserved in the melt. In contrast, the ditelluride counterpart is absent in the Ge-Te phase diagram, which shows only a single compound, monotelluride GeTe. Phase-change materials based on GeTe have become a technologically important class of solids, and their structure and properties are also widely studied. Surprisingly, very scarce information is available for alloys having GeTe 2 stoichiometry. Using a fast quenching procedure in silica capillaries, high-energy X-ray diffraction, and Raman spectroscopy supported by first-principles simulations, we show that bulk glassy GeTe 2 differs substantially from the lighter GeX 2 members, revealing 46% of trigonal germanium, 31% of three-fold coordinated tellurium, and only 20% of edge-sharing tetrahedra or pyramids. The fraction of homopolar Ge-Ge bonds is low; however, the population of dominant Te-Te dimers and Te n oligomers, n <= 10, appears to be significant. The complex structural and chemical topology of g-GeTe 2 is directly related to the thermodynamic metastability of germanium ditelluride, schematically represented by the following reaction: GeTe 2 $\rightleftarrows$ GeTe + Te. Disproportionation is complete above liquidus in the temperature range of semiconductor-metal transition, and the dense metallic GeTe 2 liquid, mostly consisting of five-fold coordinated Ge species, exhibits high fluidity, strong fragility (m = 99 ± 5), and presumably a fast structural transformation rate combined with low atomic mobility in the vicinity of the glass transition temperature, favorable for reliable long-term data retention in nonvolatile memories. The observed and predicted characteristic features make GeTe 2 a promising precursor for the next generation of phase-change materials, especially coupled with additional metal doping, depolymerizing the tetrahedral interconnected glass network and accelerating (sub)nanosecond crystallization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Tellurite Adsorption onto Bacterial Surfaces

Tellurium (Te) is an emerging contaminant and its chemical transformation in the environment is strongly influenced by microbial processes. In this study, we investigated the adsorption of tellurite [Te(IV), TeO 3 2- ] onto the common soil bacterium Bacillus subtilis. Thiol-blocking experiments were carried out to investigate the role of cell surface sulfhydryl sites in tellurite binding, and extended X-ray absorption fine structure (EXAFS) spectroscopy was performed to determine the chemical speciation of the adsorbed tellurite. The results indicate that tellurite reacts with sulfhydryl functional groups in the extracellular polymeric substances (EPS) produced by B. subtilis. Upon binding to sulfhydryl sites in the EPS, the Te changes from Te-O bonds to Te-S coordination. Further analysis of the surface-associated molecules shows that the EPS of B. subtilis contain proteins. Removal of the proteinaceous EPS dramatically decreases tellurite adsorption and the sulfhydryl surface site concentration. These findings indicate that sulfhydryl binding in EPS plays a key role in tellurite adsorption on bacterial surfaces.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Quantum Imaging of Magnetic Phase Transitions and Spin Fluctuations in Intrinsic Magnetic Topological Nanoflakes

Topological materials featuring exotic band structures, unconventional current flow patterns, and emergent organizing principles offer attractive platforms for the development of next-generation transformative quantum electronic technologies. The family of MnBi 2 T e4 (Bi 2 Te 3 )n materials is naturally relevant in this context due to their nontrivial band topology, tunable magnetism, and recently discovered extraordinary quantum transport behaviors. Despite numerous pioneering studies, to date, the local magnetic properties of MnBi 2 Te 4 (Bi 2 Te 3 )n remain an open question, hindering a comprehensive understanding of their fundamental material properties. Exploiting nitrogen-vacancy (NV) centers in diamond, we report nanoscale quantum imaging of magnetic phase transitions and spin fluctuations in exfoliated MnBi 2 Te 4 (Bi 2 Te 3 )n flakes, revealing the underlying spin transport physics and magnetic domains at the nanoscale. Furthermore, our results highlight the unique advantage of NV centers in exploring the magnetic properties of emergent quantum materials, opening new opportunities for investigating the interplay between topology and magnetism.

Antiferromagnetic materials↗
DOE OSTI2020

High Thermoelectric Performance in the New Cubic Semiconductor AgSnSbSe 3 by High-Entropy Engineering

We investigate the structural and physical properties of the AgSn m SbSe m+2 system with m = 1-20 (i.e., SnSe matrix and ~5-50% AgSbSe 2 ) from atomic, nano, and macro length scales. We find the 50:50 composition, with m = 1 (i.e., AgSnSbSe 3 ), forms a stable cation-disordered cubic rock-salt p-type semiconductor with a special multi-peak electronic valence band structure. AgSnSbSe 3 has an intrinsically low lattice thermal conductivity of ~0.47 W m -1 K -1 at 673 K owing to the synergy of cation disorder, phonon anharmonicity, low phonon velocity, and low-frequency optical modes. Furthermore, Te alloying on Se sites creates a quinary high-entropy NaCl-type solid solution AgSnSbSe 3-x Te x with randomly disordered cations and anions. The extra point defects and lattice dislocations lead to glass-like lattice thermal conductivities of ~0.32 W m -1 K -1 at 723 K and higher hole carrier concentration than AgSnSbSe 3 . Concurrently, the Te alloying promotes greater convergence of the multiple valence band maxima in AgSnSbSe 1.5 Te 1.5 , the composition with the highest configurational entropy. Facilitated by these favorable modifications, we achieve a high average power factor of ~9.54 μW cm -1 K -2 (400-773 K), a peak thermoelectric figure of merit ZT of 1.14 at 723 K, and a high average ZT of ~1.0 over a wide temperature range of 400-773 K in AgSnSbSe 1.5 Te 1.5 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗