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At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Gd3Bi(Ru2O7)2 by Materials Project

Gd3Bi(Ru2O7)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent BiO8 hexagonal bipyramids, edges with four equivalent GdO8 hexagonal bipyramids, and edges with six RuO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.54 Å. There are two inequivalent Ru4+ sites. In the first Ru4+ site, Ru4+ is bonded to six equivalent O2- atoms to form RuO6 octahedra that share corners with six equivalent RuO6 octahedra and edges with six equivalent GdO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 49°. All Ru–O bond lengths are 2.01 Å. In the second Ru4+ site, Ru4+ is bonded to six O2- atoms to form RuO6 octahedra that share corners with six RuO6 octahedra, edges with two equivalent BiO8 hexagonal bipyramids, and edges with four equivalent GdO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 49°. There are four shorter (2.00 Å) and two longer (2.02 Å) Ru–O bond lengths. Bi3+ is bonded to eight O2- atoms to form distorted BiO8 hexagonal bipyramids that share edges with six equivalent GdO8 hexagonal bipyramids and edges with six equivalent RuO6 octahedra. There are two shorter (2.27 Å) and six longer (2.53 Å) Bi–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Gd3+ and one Bi3+ atom to form a mixture of edge and corner-sharing OGd3Bi tetrahedra. In the second O2- site, O2- is bonded to two equivalent Gd3+ and two Ru4+ atoms to form a mixture of distorted edge and corner-sharing OGd2Ru2 tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Gd3+, two equivalent Ru4+, and one Bi3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrGdNiO4 by Materials Project

GdSrNiO4 is (La,Ba)CuO4-derived structured and crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.39–2.73 Å. Gd3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Gd–O bond distances ranging from 2.28–2.71 Å. Ni3+ is bonded to six O2- atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of Ni–O bond distances ranging from 1.91–2.13 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to one Sr2+, four equivalent Gd3+, and one Ni3+ atom to form distorted OSrGd4Ni octahedra that share corners with seventeen OSr2Gd2Ni2 octahedra, edges with eight OSrGd4Ni octahedra, and faces with four equivalent OSr2Gd2Ni2 octahedra. The corner-sharing octahedra tilt angles range from 0–52°. In the second O2- site, O2- is bonded to four equivalent Sr2+, one Gd3+, and one Ni3+ atom to form distorted OSr4GdNi octahedra that share corners with seventeen OSr2Gd2Ni2 octahedra, edges with eight OSrGd4Ni octahedra, and faces with four equivalent OSr2Gd2Ni2 octahedra. The corner-sharing octahedra tilt angles range from 0–53°. In the third O2- site, O2- is bonded to two equivalent Sr2+, two equivalent Gd3+, and two equivalent Ni3+ atoms to form a mixture of distorted corner, edge, and face-sharing OSr2Gd2Ni2 octahedra. The corner-sharing octahedra tilt angles range from 9–53°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GdS2 by Materials Project

GdS2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Gd3+ is bonded in a 12-coordinate geometry to twelve equivalent S+1.50- atoms. All Gd–S bond lengths are 3.24 Å. S+1.50- is bonded to six equivalent Gd3+ and six equivalent S+1.50- atoms to form a mixture of edge, face, and corner-sharing SGd6S6 cuboctahedra. All S–S bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2GdMoO6 by Materials Project

Ba2GdMoO6 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form distorted BaO12 cuboctahedra that share corners with twelve equivalent BaO12 cuboctahedra, faces with six equivalent BaO12 cuboctahedra, faces with four equivalent GdO6 octahedra, and faces with four equivalent MoO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.87–3.22 Å. Gd3+ is bonded to six O2- atoms to form GdO6 octahedra that share corners with six equivalent MoO6 octahedra and faces with eight equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–12°. There are a spread of Gd–O bond distances ranging from 2.27–2.29 Å. Mo5+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with six equivalent GdO6 octahedra and faces with eight equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–12°. There are a spread of Mo–O bond distances ranging from 1.98–2.05 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Gd3+, and one Mo5+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ba2+, one Gd3+, and one Mo5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ba2+, one Gd3+, and one Mo5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Gd3(TeO6)2 by Materials Project

Li3Gd3Te2O12 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Li1+ is bonded to four equivalent O2- atoms to form LiO4 tetrahedra that share corners with four equivalent TeO6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Li–O bond lengths are 1.92 Å. Gd3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.40 Å) and four longer (2.51 Å) Gd–O bond lengths. Te6+ is bonded to six equivalent O2- atoms to form TeO6 octahedra that share corners with six equivalent LiO4 tetrahedra. All Te–O bond lengths are 1.96 Å. O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Gd3+, and one Te6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Flowsheet for the Neutralization of Accelerated Basin De-inventory (ABD) Material

Under the Accelerated Basin De-inventory (ABD) program H-Canyon will be dissolving aluminum spent nuclear fuel (ASNF) and then neutralizing that solution without performing head-end strike or uranium recovery operations. After dissolution in H-Canyon the material will be neutralized to a free hydroxide concentration of either 0.6 M or 1.2 M to meet the waste acceptance criteria for transfer to the SRS Concentration, Storage and Transfer Facility (CSTF). In order to ensure the material could be successfully neutralized and transferred, SRNL completed experiments with simulated H-Canyon dissolver solutions. Two bounding simulants were developed based on the expected compositions of ASNF to be dissolved, one containing only Gd as the neutron poison and one containing Fe as an additional poison.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

How Gaps in Time-Series Data Affect Asteroseismic Interpretation

Most pulsating white dwarf stars pulsate with many periods, each of which is a probe of their interior, which has made asteroseismolgy of these stars an active field. However, disentangling the multiple periodicities requires long, uninterrupted strings of data. We briefly describe the history of multi-site observing campaigns that culminated in the development of the Whole Earth Telescope in the late 1980s that still functions today. Through examples from the May 1990 campaign on GD 358, we show how critical it is to eliminate periodic gaps in data to greatly reduce aliasing in Fourier Transforms normally used to analyze the frequency content of pulsating white dwarfs. We close with a brief description of space satellite-based data, along with the advantages and disadvantages of these data compared to ground-based data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Deformation Behavior of β Phase in a WE54 Magnesium Alloy

Second phases play a significant role in the development of high-performance magnesium alloys with rare earth elements. Here, in situ tensile tests combined with synchrotron radiation were carried out to investigate the deformation behavior of β phases in a WE (Mg–Y–Gd–Nd) alloy. By lattice strain analysis, it was found that micro load continuously transferred from the soft α-Mg matrix to the hard β phases during the whole plastic deformation, while this behavior was much more obvious at the beginning of deformation. Based on diffraction peak broadening, Williamson–Hall (W–H) plotting was used to study the microstrain of β phases. The results showed that the microstrain of β phases increased rapidly within 4% plastic strain and reached the maximum at plastic strain of ~6.5%. Since the β phases acted as hard phases, the microstrain was considered as a sign of the stress concentration near phase interfaces. It was also suggested that the effective release of local stress concentration at the β/α-Mg interface benefited the ductility of the WE alloy by the plastic deformation of β phases and phase interface sliding.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dual 3D Ceramic Textile Electrodes: Fast Kinetics for Carbon Oxidation Reaction and Oxygen Reduction Reaction in Direct Carbon Fuel Cells at Reduced Temperatures

Abstract Direct carbon fuel cells (DCFCs) are an efficient energy‐conversion technology capable of generating electricity with carbon‐dioxide‐capture chemistry with solid carbon as fuels. The efficiency and performance of DCFCs depend on the kinetics of the carbon oxidation reactions (COR) and the oxygen reduction reactions (ORR), each occurring at anode and cathode, respectively. The limited active sites paired with reduced temperatures greatly decrease the efficiency of the electrochemical reactions. Ultraporous dual‐3D ceramic textiles (dual‐3DCT) are integrated into electrolyte‐supported DCFCs to enhance charge and mass transfer at the electrodes. Improved COR at the anode is achieved by the synergy between the 3DCT NiO–Ce 0.8 Gd 0.2 O 1.95 (GDC) structure and optimal carbon fuel choice. In a comparative study, DCFCs using graphitic carbon (GC) as fuel show the best COR performance when compared to DCFCs utilizing alternative fuels such as carbon black (CB) and activated carbon (AC). The 3DCT Sm 0.5 Sr 0.5 CoO 3‐δ –GDC (SSC–GDC) composite cathode shows electrochemical performance superior to that of the conventional screen‐printed SSC–GDC. A peak power density of 392 mW cm −2 at 600 °C is obtained in a DCFC using the 3DCT‐anode/electrolyte/3DCT‐cathode configuration, an unprecedented value for any reported DCFC as of yet. This points toward promising applications of dual‐3DCT electrodes for reduced‐temperature DCFCs.

Bian, Wenjuan↗
DOE OSTI2022

Visualization of Tunable Weyl Line in A–A Stacking Kagome Magnets

Abstract Kagome magnets provide a fascinating platform for a plethora of topological quantum phenomena, in which the delicate interplay between frustrated crystal structure, magnetization, and spin–orbit coupling (SOC) can engender highly tunable topological states. Here, utilizing angle‐resolved photoemission spectroscopy, the Weyl lines are directly visualized with strong out‐of‐plane dispersion in the A–A stacked kagome magnet GdMn 6 Sn 6 . Remarkably, the Weyl lines exhibit a strong magnetization‐direction‐tunable SOC gap and binding energy tunability after substituting Gd with Tb and Li, respectively. These results not only illustrate the magnetization direction and valence counting as efficient tuning knobs for realizing and controlling distinct 3D topological phases, but also demonstrate AMn 6 Sn 6 (A = rare earth, or Li, Mg, or Ca) as a versatile material family for exploring diverse emergent topological quantum responses.

Cheng, Zi‐Jia↗
DOE OSTI2024

Tuning the Spin Transition and Carrier Type in Rare-Earth Cobaltates via Compositional Complexity

There is growing interest in material candidates with properties that can be engineered beyond traditional design limits. Compositionally complex oxides (CCO), often called high entropy oxides, are excellent candidates, wherein a lattice site shares more than four cations, forming single-phase solid solutions with unique properties. However, the nature of compositional complexity in dictating properties remains unclear, with characteristics that are difficult to calculate from first principles. Here, in this study, compositional complexity is demonstrated as a tunable parameter in a spin-transition oxide semiconductor La 1- x (Nd, Sm, Gd, Y) x/4 CoO 3 , by varying the population x of rare earth cations over 0.00≤ x≤ 0.80. Across the series, increasing complexity is revealed to systematically improve crystallinity, increase the amount of electron versus hole carriers, and tune the spin transition temperature and on-off ratio. At high a population (x = 0.8), Seebeck measurements indicate a crossover from hole-majority to electron-majority conduction without the introduction of conventional electron donors, and tunable complexity is proposed as new method to dope semiconductors. First principles calculations combined with angle resolved photoemission reveal an unconventional doping mechanism of lattice distortions leading to asymmetric hole localization over electrons. Thus, tunable complexity is demonstrated as a facile knob to improve crystallinity, tune electronic transitions, and to dope semiconductors beyond traditional means.

36 MATERIALS SCIENCE↗
DOE OSTI2025

From the Discovery of the Giant Magnetocaloric Effect to the Development of High‐Power‐Density Systems

Caloric cooling and heating promise an efficient and reliable alternative to ubiquitous vapor-compression technology. In 1976, the very first near-room-temperature caloric system is developed, but it took another 20 years for this technology to fully bloom and gain global attention. The discovery of the giant magnetocaloric effect in Gd 5 Si 2 Ge 2 and the advance of the first long-operating magnetic refrigerator, both in 1997, due to the Ames National Laboratory and Astronautics Corporation of America cooperation, are two milestones that sparked ongoing interest in caloric research, which continues to thrive to this day. This review presents a brief history of caloric heat pumping, from the discovery of the magnetocaloric effect to the most recent developments in materials and systems. The contributions of Ames National Laboratory of the U.S. Department of Energy are highlighted, celebrating its 30-year anniversary in caloric research and paying tribute to two outstanding scientists, Vitalij K. Pecharsky and Karl A. Gschneidner, Jr., who inspired the caloric community for decades. The paper concludes with insights into remaining research and development challenges that must be addressed to enable the market transition of caloric technology and its widespread adoption.

caloric materials↗
DOE OSTI2026

Phase Diagrams and Piezoelectric Properties of Wurtzite Al1-x-yScxGdyN Heterostructural Alloys

Ternary nitride alloys based on wurtzite AlN are a promising platform to realize functional materials, particularly ferroelectrics and optical emitters, that can smoothly integrate with conventional microelectronics. Here, a strategic design is presented to enable multifunctional materials by substituting multiple elements into AlN to create quaternary nitride alloys. By combining computational predictions and combinatorial thin film synthesis, the phase diagram of these quaternary Al-Sc-Gd-N alloys (or pseudo-ternary heterostructural AlN-ScN-GdN alloys) is successfully predicted as a function of effective temperature, and we experimentally grow Al1-x-xScxGdyN thin films for the first time. It is revealed that Al1-x-xScxGdyN crystallizes in a wurtzite-derived structure for X + y <~ 0.35, consistent with the calculated phase diagram. The computational investigation explores whether co-substitution induces cooperative effects on these alloys' piezoelectric and ferroelectric properties, finding that it is beneficial for reducing the polarization switching barrier. We calculate that Al1-x-xScxGdyN thin films should display ferroelectric switching. This is supported by our experimental measurements of a high optical bandgap, enhanced piezoelectric coefficient, and a change in the calculated polarization switching mechanism, and we achieve preliminary ferroelectric switching that experimentally realizes the prediction. Overall, our work sets the foundation toward quaternary wurtzite-nitride-based multifunctional materials, including piezoelectrics, ferroelectrics, and possibly even multiferroics.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Experimental and Theoretical Studies of the Surface Oxidation Process of Rare–Earth Tritellurides

Recent studies have established Van der Waals (vdW) layered and 2D rare-earth tritellurides (RTe 3 ) as superconductors and near room-temperature charge density wave (CDW) materials. Their environmental stability raises natural concern owing to aging/stability effects observed in other tellurium-based layered crystals. Here, the results establish the stability and environmental aging characteristics of these RTe 3 systems involving a variety of metals such as La, Nd, Sm, Gd, Dy, and Ho. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that all the RTe 3 sheets oxidize to form thin TeO x layers that are primarily confined to the surface, edges, and grain boundaries. Time-resolved in situ Raman spectroscopy measurements are used to understand the kinetics of the oxidization process for different lanthanide metal cations and establish their relative stability/resilience to oxidization. Overall results indicate that the vdW layers show higher air stability as the 4f electron number decreases going from Ho to La, resulting in the most stable LaTe 3 compared to the least stable HoTe 3 . Comprehensive quantum mechanical simulations reveal that environmental degradation originates from a strong oxidizing reaction with O 2 molecules, while humidity (H 2 O) plays a negligible role unless Te vacancies are present. Moreover, the simulations explain the effects of 4f electrons on the work function and Te vacancies formation, which directly impact the aging characteristics of RTe 3 layers. Interestingly, optical and electrical measurements show that the CDW response is still observed in aged RTe 3 layers owing to the presence of underlying pristine/nonoxidized RTe 3 layers, except CDW transition temperatures increase due to the thickness effect. Overall results offer the first in-depth environmental aging studies on these materials, which can be applied to engineer and design their chemical stability, surface properties, and overall CDW characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhanced Surface Interactions Enable Fast Li + Conduction in Oxide/Polymer Composite Electrolyte

Abstract Li + ‐conducting oxides are considered better ceramic fillers than Li + ‐insulating oxides for improving Li + conductivity in composite polymer electrolytes owing to their ability to conduct Li + through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li + ‐insulating oxides (fluorite Gd 0.1 Ce 0.9 O 1.95 and perovskite La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.55 ) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)‐based polymer composite electrolytes, each with a Li + conductivity above 10 −4 S cm −1 at 30 °C. Li solid‐state NMR results show an increase in Li + ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2‐site occupancy originates from the strong interaction between the O 2− of Li‐salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li + transport. All‐solid‐state Li‐metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.

Wu, Nan↗
DOE OSTI2023

Elusive Double Perovskite Iodides: Structural, Optical, and Magnetic Properties

Halide double perovskites [A 2 M I M III X 6 ] are an important class of materials that have garnered substantial interest as non-toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs 2 NaLnI 6 (Ln=Ce, Nd, Gd, Tb, Dy). Finally, the complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Chemical Bond Covalency in Superionic Halide Solid‐State Electrolytes

Abstract Halide solid‐state electrolytes (SSEs) are promising superionic conductors with high oxidative stability and ionic conductivity, making them attractive for all‐solid‐state lithium‐ion batteries. However, most studies have focused on ion‐stacking structures, overlooking the role of bond characteristics in ionic transport. Here, we investigate bond dynamics and the superionic transition (SIT) in bromide electrolyte, Li 3 InBr 6 , using synchrotron X‐ray techniques and ab initio molecular dynamics (AIMD) simulations. We demonstrate that the SIT in halide SSEs is driven by a thermally induced transition in bonding character (ionic to covalent) rather than a change in crystal phase. AIMD simulations further reveal enhanced Li⁺ diffusion and collective anion motion at elevated temperatures. Expanding our study to Li 3 LnBr 6 (Ln = Gd, Tb, Ho, Tm, and Lu), we confirm the widespread occurrence of SIT in this material class, with Li 3 GdBr 6 exhibiting the highest ionic conductivity (5.2 mS cm −1 at 298 K). More importantly, the ionic‐covalent transition is highly tunable through electrolyte modifications, such as cation/anion substitution and synthesis methods. Our findings provide a new perspective on ionic transport, highlighting the critical role of chemical bond characteristics in halide SSEs.

Chemistry↗
DOE OSTI2026

A Comparative Study of Ethanol Upgrading to Butadiene Over Rare Earth Elements Incorporated in Dealuminated Beta Zeolites

Copper and rare earth element-containing dealuminated Beta zeolites (CuREE/deAlBeta) are promising catalysts for the conversion of ethanol to C 3+ olefins en route to sustainable aviation fuel. Product selectivities over CuREE/deAlBeta depend on the identity of the REE. Here, in this study, a suite of La/deAlBeta catalysts of varied La loading are prepared, and their reactivities, selectivities, and apparent C-C coupling kinetics in the cascade reaction between ethanol and acetaldehyde are reported. Ex situ and in situ titrations to quantify Lewis acidic La sites quantify distinct numbers of sites, suggesting a distribution of site types. Across a series of REE/deAlBeta catalysts (REE = Y, La, Lu, Yb, Gd), the selectivity to secondary products correlates with the pyridine heats of adsorption at REE Lewis acid sites. The turnover frequency (per Lewis acid site) for C–C coupling was similar across the series of REE/deAlBeta catalysts. Y/deAlBeta and La/deAlBeta, which have the most disparate secondary product selectivities, had similar kinetics for C–C coupling. These findings demonstrate the complexity of quantifying active sites in REE/deAlBeta zeolites, and the sensitivity of the selectivity, but not the reactivity for C–C coupling, to the identity of the REE atom in REE/deAlBeta zeolites.

alcohol upgrading↗