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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ultra low noise materials and devices for cryogenic superconductors and quantum bits

Materials, products, methods of use and fabrication thereof are disclosed. The materials are particularly well suited for application in products such as superconducting devices and quantum computing, due to ability to avoid undesirable effects from inherent noise and decoherence. The materials are formed from select isotopes having zero nuclear spin into a single crystal-phase film or layer of thickness depending on the desired application of the resulting device. The film/layer may be suspended or disposed on a substrate. The isotopes may be enriched from naturally-occurring sources of isotopically mixed elemental material(s). The single crystal is preferably essentially devoid of structural defects such as grain boundaries, inclusions, impurities and lattice vacancies.

Pereverzev, Sergey↗
DOE OSTI2023

The impact of feedstock size and composition on the hydrothermal growth of (U,Th)O 2

Bulk crystal growth of refractory oxides requires unique approaches, and the U x Th 1-x O 2 solid solution is no exception. Hydrothermal transport reactions of U 0.1 Th 0.9 O 2 onto ThO 2 seeds with feedstocks comprised of U 0.1 Th 0.9 O 2 or mixtures of UO 2 and ThO 2 with a nominal composition of U 0.1 Th 0.9 O 2 are investigated with µ-Raman spectroscopy and X-ray fluorescence. In each case, the trends in stoichiometry as a function of distance from the seed are analyzed and the deviations from the nominal stoichiometry discussed. When the feedstock is composed of mixed oxides, the particle surface area’s influence on the feedstock dissolution rate is the dominant factor and can produce U-rich stoichiometries as high as U 0.75 Th 0.25 O 2 . When composed solely of U 0.1 Th 0.9 O 2 , the total growth amount depends on the particle size, but the obtained stoichiometry is the product of differing solubilities. Although the U0.1Th0.9O 2 feedstock produces the most homogeneous growth, the ending growth of the smallest particle UO 2 /ThO 2 mixture yields the stoichiometry closest to U 0.1 Th 0.9 O 2 . How to obtain desired stoichiometries from mixtures by matching the particle size and solubilities is briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Scaling up of High-Performance Single Crystalline Ni-rich Cathode Materials (CRADA 509)

This is a collaborative effort between Battelle Memorial Institute as manager and operator of Pacific Northwest National Laboratory (PNNL) and Albemarle Corporation (“Participant”) to develop and scale up an innovative and low-cost synthesis approach for preparing high-performance single crystalline Ni-rich cathode materials, i.e., LiNi0.8Mn0.1Co0.1O2 (NMC811) and LiNi0.9Mn0.05Co0.05O2 (NMC90) for next-generation LIBs. At the end of this project, the team will (1) develop a cost-effective synthesis approach for preparing single crystalline MNC811 (>200 mAh/g) and NMC90 (>210 mAh/g) by using advanced lithium salts, (2) address the performance issues of single crystals prepared from large-scale synthesis, and (3) demonstrate the processing/scaling up capabilities of up to 1 kg/batch of high-performance NMC811 and NMC90 single crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural Insights into the Vapochromic Behavior of Pt- and Pd-Based Compounds

Anionic complexes having vapochromic behavior are investigated: [K(H 2 O)][M(ppy)(CN) 2 ], [K(H 2 O)][M(bzq)(CN) 2 ], and [Li(H 2 O) n ][Pt(bzq)(CN) 2 ], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H 2 O)][Pt(ppy)(CN) 2 ] crystallizes in the Pbca space group and is isostructural to [K(H 2 O)][Pd(ppy)(CN) 2 ]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. Furthermore, the local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High‐Temperature Mechanical Behavior of Single‐Crystal FeCrAl Alloy Under In Situ Micropillar Compression

FeCrAl cladding is one of the candidate materials for the near‐term accident‐tolerant fuel technologies under development. Research on high‐temperature mechanical behaviors of single‐crystal FeCrAl alloy is rather limited. Previous studies have reported the mechanical property of low‐index orientation in single‐crystal FeCrAl alloy at room temperature. However, the critical resolved shear stress to activate slip systems can be orientation and temperature dependent. Here, single‐crystal grains in a coarse‐grained FeCrAl alloy with different crystallographic orientations are selected to preferentially activate {110}<111> slip systems or {112}<111> slip systems. Micropillars are fabricated in the selected single‐crystal grains and tested at elevated temperatures in situ in a scanning electron microscope. The critical resolved shear stresses of {110}<111> slip systems and {112}<111> slip systems are determined at various temperatures. The critical resolved shear stress shows a temperature dependence and orientation independence. This study provides important insight for understanding the deformation mechanisms of FeCrAl alloys at elevated temperatures.

Sun, Tianyi↗
DOE OSTI2020

Single-Crystal Polycationic Polymers Obtained by Single-Crystal-to-Single-Crystal Photopolymerization

The efficient preparation of single-crystalline ionic polymers and fundamental understanding of their structure–property relationships at the molecular level remains a challenge in chemistry and materials science. Herein, we observe the single-crystal structure of a highly ordered polycationic polymer (polyelectrolyte) and its proton conductivity. The polyelectrolyte single crystals can be prepared on a gram-scale in quantitative yield, by taking advantage of an ultraviolet/sunlight-induced topochemical polymerization, from a tricationic monomer—a self-complementary building block possessing a preorganized conformation. A single-crystal-to-single-crystal photopolymerization was revealed unambiguously by in situ single-crystal X-ray diffraction analysis, which was also employed to follow the progression of molecular structure from the monomer, to a partially polymerized intermediate, and, finally, to the polymer itself. Collinear polymer chains are held together tightly by multiple Coulombic interactions involving counterions to form two-dimensional lamellar sheets (1 nm in height) with sub-nanometer pores (5 Å). The polymer is extremely stable under 254 nm light irradiation and high temperature (above 500 K). The extraordinary mechanical strength and environmental stability—in combination with its impressive proton conductivity (~3 × 10 –4 S cm –1 )—endow the polymer with potential applications as a robust proton-conducting material. By marrying supramolecular chemistry with macromolecular science, the outcome represents a major step toward the controlled synthesis of single-crystalline polyelectrolyte materials with perfect tacticity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Characterization of n-Type Iodine-Doped and Indium-Doped CdTe/Cd-Se-Te Thin Films Fabricated by Close-Spaced Sublimation Epitaxy

In this study, n-type CdTe thin films, specifically iodine-doped CdTe (CdTe:I), indium-doped CdTe (CdTe:In), and indium-doped Cd-Se-Te (CST:In), were synthesized using close-spaced sublimation epitaxy (CSSE). Characterization techniques secondary ion mass spectrometry (SIMS), electron backscatter diffraction (EBSD), Hall-effect measurements, and time-resolved photoluminescence (TRPL) were employed to analyze the chemical, structural, and electronic properties of these materials. The results indicated epitaxial single crystal CSSE films grew on the single crystal substrates, with carrier density ranging from 10^14 - 10^16 cm -3 , and after post-annealing, the minority-carrier lifetimes reach near the radiative limit. Additionally, a preliminary exploration of homojunction structures with an n- type (CdTe:In /CST:In /CdTe:I) /CdTe:P /Cu /Mo configuration was performed. The best device performance was achieved with CdTe:I including CdS aiding in band alignment, resulting in a power conversion efficiency (..eta..) of 2.61% with open circuit voltage (Voc) of 850 mV, fill factor (FF) of 47.8%, and short-circuit current (Jsc) of 6.44 mA/cm 2 . The observed low Jsc and efficiency may be attributed to a buried junction and a poor interface, due to dopant interdiffusion. Consequently, further investigations focusing on interface optimization, diffusion blocking, and reduced recombination through passivation, are crucial to enhancing the efficiency of CSSE CdTe homojunction devices in the future.

cadmium compounds↗
DOE OSTI2020

Magnetic properties of ferrimagnetic Mn 3 Si 2 Se 6

The physical properties of Mn 3 Si 2 Se 6 have been investigated using single crystals grown by iodine-assisted vapor transport. Additionally, the material possesses a ferrimagnetic ground state and the properties are similar to those in the isostructural compound Mn 3 Si 2 Se 6 . Furthermore, in these trigonal materials, the dominant magnetic exchanges are antiferromagnetic and intrinsically frustrated, leading to a variety of competing ground states. In Mn 3 Si 2 Se 6 , the Curie temperature is TC = 67(1)K, which is slightly lower than that of Mn 3 Si 2 Se 6 where TC = 78K. The anisotropy field is also smaller in the selenide relative to the telluride. In both materials, short-range correlations likely exist well-above TC. Neutron single crystal diffraction data on Mn 3 Si 2 Se 6 suggest a collinear ferrimagnetic structure with the moments tilting out of the ab-plane in zero-field. Finally, the magnetization of vapor grown Mn 3 Si 2 Se 6 is shown for comparison; these vapor grown crystals do not show a sharp onset of magnetic anisotropy above 300K as was previously observed for melt grown Mn 3 Si 2 Se 6 crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Methods for Determining the Infrared Complex Refractive Indices n (λ) and k (λ) from Organic Solid Powders: Comparison of a Sucrose Single Crystal and a Pressed Pellet

There exists a need to measure optical constants n and k for many materials, especially organic solids in the infrared spectral region, but at present, there are only two established methods for making such measurements: single-angle (SA) reflectance and infrared spectroscopic ellipsometry (IRSE). The former derives the n/k vectors via measurement of the change in the amplitude of light reflected from the sample and then uses the Kramers–Kronig transform, while the latter measures the change in polarization of the reflected light from the sample to derive n/k. Here we make a direct comparison between the n/k vectors derived from SA measurements of a sucrose single crystal and the n/k values obtained after the crystal had been crushed, ground to powder, and pressed into a pellet form. The pellet was measured not only by SA but also via the IRSE method, and we found that pressing specular-quality pellets was critical, especially for the SA data. The n/k values of this typical organic molecule all agree to within 0.04 root-mean-square error, confirming that a pressed pellet can be used instead of a crystal to derive the intrinsic n/k vectors. In conclusion, this result is important for the many organic materials that, unlike sugar, do not have centimeter-sized crystals readily available.

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

Recent developments on 2D magnetic materials: challenges and opportunities

The emergence of two-dimensional (2D) magnetic materials exhibiting strong magnetization at ultrathin limits above room temperature are promising for miniaturization of devices beyond Moore’s law for future energy efficient nano-electronic devices. Here, the current status, different mechanisms for the existence of magnetism, spin current injection and other magnetic properties of monolayer to few-layers of various 2D magnetic materials are reviewed. Some of the promising applications of these materials are spintronics devices such as spin valves, spin tunnel field-effect transistors, and spin filtering magnetic tunnel junctions. Due to the tunable electronic properties of these 2D materials, it's quite interesting to inject the spin current with suitable ferromagnetic contacts. For instance,black phosphorus is a layered material with a small Schottky barrier height capable of injecting spin current. This review includes many recently explored 2D magnetic materials ranging from exfoliated 2D crystals to CVD grown materials from single to several layers, demonstrating tunable layer dependent magnetic properties. We also explore some of the promising theoretical study based on 2D magnetic compounds such as 2D alkali-based chromium chalcogenides, which shows ferromagnetic as well as semiconducting behavior. The layer-dependent magnetic ordering has been observed in layered compounds like 1T-CrTe 2 , VSe 2 , CrI 3 , and Fe 3 GeTe 2 , which have great potential for the future applications in magnetic based electronic devices. Finally, we emphasize the challenges, opportunities and future directions of the 2D magnetic materials, where new discoveries might have outstanding impact in transformational scientific breakthroughs towards memory, spintronics, optoelectronics and other multifunctional device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Transuranium Sulfide via the Boron Chalcogen Mixture Method and Reversible Water Uptake in the NaCu T S 3 Family

The behavior of 5f electrons in soft ligand environments makes actinides, and especially transuranium chalcogenides, an intriguing class of materials for fundamental studies. Due to the affinity of actinides for oxygen, however, it is a challenge to synthesize actinide chalcogenides using non-metallic reagents. Using the Boron Chalcogen Mixture (BCM) method, we achieved the synthesis of the transuranium sulfide NaCuNpS 3 starting from the oxide reagent, NpO 2 . Via the same synthetic route, the isostructural composition of NaCuUS 3 was synthesized and the material contrasted with NaCuNpS 3 . Single crystals of the U-analog, NaCuUS 3 , were found to undergo an unexpected reversible hydration process to form NaCuUS 3 ·xH 2 O (x ≈ 1.5). Here, a large combination of techniques was used to fully characterize the structure, hydration process, and electronic structures, specifically a combination of single crystal, powder, high temperature powder X-ray diffraction, extended X-ray ab-sorption fine structure, infrared, and inductively coupled plasma spectroscopies, thermogravimetric analysis, and density functional theory calculations. The outcome of these analyses enabled us to determine the composition of NaCuUS 3 ·xH 2 O and obtain a structural model that demonstrated the retention of the local structure within the [CuUS 3 ] – layers throughout the hydration-dehydration process. Band structure, density of states, and Bader charge calculations for NaCuUS 3 , NaCu-US 3 ·xH 2 O, and NaCuNpS 3 along with X-ray absorption near edge structure, UV-vis-NIR and work function measurements on ACuUS 3 (A = Na, K, and Rb) and NaCuUS 3 ·xH 2 O samples were carried out to demonstrate that electronic properties arise from the [CuTS 3 ] – layers and show surprisingly little dependence on the interlayer distance.

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

Photoinduced anisotropic lattice dynamic response and domain formation in thermoelectric SnSe

Identifying and understanding the mechanisms behind strong phonon–phonon scattering in condensed matter systems is critical to maximizing the efficiency of thermoelectric devices. To date, the leading method to address this has been to meticulously survey the full phonon dispersion of the material in order to isolate modes with anomalously large linewidth and temperature-dependence. Here we combine quantitative MeV ultrafast electron diffraction (UED) analysis with Monte Carlo based dynamic diffraction simulation and first-principles calculations to directly unveil the soft, anharmonic lattice distortions of model thermoelectric material SnSe. A small single-crystal sample is photoexcited with ultrafast optical pulses and the soft, anharmonic lattice distortions are isolated using MeV-UED as those associated with long relaxation time and large displacements. We reveal that these modes have interlayer shear strain character, induced mainly by c -axis atomic displacements, resulting in domain formation in the transient state. These findings provide an innovative approach to identify mechanisms for ultralow and anisotropic thermal conductivity and a promising route to optimizing thermoelectric devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

A miniature multi-anvil apparatus using diamond as anvils—MDAC: Multi-axis diamond anvil cell

The diamond anvil cell (DAC) has been widely used in high-pressure research. Despite significant progress over the past five decades, the opposed anvil geometry in the DAC inevitably leads to a disk-shaped sample configuration at high pressure. This intrinsic limitation is largely responsible for the large pressure and temperature gradients in the DAC, which often compromise precise experiments and their characterizations. Here, we designed and fabricated a multi-axis diamond anvil cell (MDAC) by adopting the concept of a multi-anvil apparatus but using single crystal diamonds as the anvil material. Preliminary data show that the MDAC can generate extreme pressure conditions above 100 GPa. The advantages of the MDAC over a traditional opposed anvil DAC include thicker, voluminous samples, quasi-hydrostatic, or designed deviatoric stress conditions, and multidirectional access windows for optical applications and x-ray probes. In this article, we present the design and performance of a prototype MDAC, as well as the application prospects in high-pressure research.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Time-resolved broadband impulsive stimulated Brillouin scattering in single crystal hematite

Impulsive stimulated Brillouin scattering (ISBS) has emerged as a noninvasive means to determine the elastic properties of transparent materials. Here, we report on time-resolved broadband ISBS reflectivity measurements in single crystal hematite, α-Fe 2 O 3 . We found that the observed transient reflectivity changes are best described by the known strain propagation model (SPM) and introduced a simple derivation of the ISBS-SPM formula based on ray tracing, which accounts for the presence of the interface. Additionally, measurements at different incident probe beam angles illustrate a plausible approach toward determining the speed of sound in transparent media without any prior knowledge of their dielectric properties and vice versa.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Imaging Polarity in Two Dimensional Materials by Breaking Friedel's Law

Friedel's law guarantees an inversion-symmetric diffraction pattern for thin, light materials where a kinematic approximation or a single-scattering model holds. Typically, breaking Friedel symmetry is ascribed to multiple scattering events within thick, non-centrosymmetric crystals. However, two-dimensional (2D) materials such as a single monolayer of MoS 2 can also violate Friedel's law, with unexpected contrast between conjugate Bragg peaks. Here, we show analytically that retaining higher order terms in the power series expansion of the scattered wavefunction can describe the anomalous contrast between hkl and $\bar{hkl}$ peaks that occurs in 2D crystals with broken in-plane inversion symmetry. These higher-order terms describe multiple scattering paths starting from the same atom in an atomically thin material. Furthermore, 2D materials containing heavy elements, such as WS 2 , always act as strong phase objects, violating Friedel's law no matter how high the energy of the incident electron beam. Experimentally, this understanding can enhance diffraction-based techniques to provide rapid imaging of polarity, twin domains, in-plane rotations, or other polar textures in 2D materials.

2D materials↗
DOE OSTI2024

Superconducting (Ba,K)Fe 2 As 2 epitaxial films on single and bicrystal SrTiO 3 substrates

The realization of single crystal and bicrystal films of superconducting materials is of great interest because they allow the investigation of the intragrain performance as well as the understanding of potential limitations in the grain boundary transparency. For many years, the realization of a high-quality (Ba,K)Fe 2 As 2 film has been challenging. Here, the realization of (Ba,K)Fe 2 As 2 epitaxial thin films on single crystal SrTiO 3 (001) and [001]-tilt-type SrTiO 3 bicrystal substrates with high superconducting properties is demonstrated. The epitaxial growth of (Ba,K)Fe 2 As 2 was enabled by implementing an undoped BaFe 2 As 2 buffer layer between the SrTiO 3 substrate and (Ba,K)Fe 2 As 2 film. The film exhibits a high T c of 38.0 K and an extremely high J c of 14.3 MA/cm 2 at 4.2 K. Artificial grain boundaries of (Ba,K)Fe 2 As 2 were also successfully achieved on bicrystals with misorientation angles up to 36.8° by the same preparation methods. The artificial grain boundaries exhibited an identical T c of 38.0 K and an excellent transfer of the grain orientation from the bicrystal substrates with high crystallinity comparable to that of the high-quality Ba(Fe,Co) 2 As 2 films. Furthermore, this enables the investigation of the intrinsic (Ba,K)Fe 2 As 2 grain boundary nature, which will clarify its potential for superconducting applications, like Josephson junctions, wires, and magnets.

(Ba,K)Fe2As2↗
DOE OSTI2022

In Situ Probing and Investigation of the Crystal Growth of Highly Correlated Intermetallics

The proposal seeks to investigate the synthetic process of a new class of highly correlated intermetallics Ce n+1 Co n Ge 3n+1 (n = 1 – 6). This family of compounds is attractive as members of the series consist of subunits found in quantum materials. With our efforts to grow single crystals, we will address the fundamental questions of 1) how do crystals that are built from subunits form during crystallization and 2) what determines how these subunits arrange. We hypothesize that the complex intergrowth structures of Ce n+1 Co n Ge 3n+1 form upon cooling by the assembly of subunit-like clusters that exist prior to crystallization in the melt. The second hypothesis is layer-by-layer growth. The third hypothesis is an alternative growth mechanism, such as the conversion of metastable structure into a different structure. By understanding the assembly of subunits, strategies to affect process could emerge, which will ultimately lead to controlled heterostructural stacking of various subunits in the growth of bulk materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electronic transport, thermal transport, thermal expansion, and magnetization in the strongly correlated metal LaNi⁢O 3

Perovskite structured LaNiO 3 is a strongly correlated metal with intriguing thermal and magnetic properties. The volume dependence of calculated and measured physical properties can add additional critical information to develop a more in-depth understanding of this strongly correlated phenomenon. Taking advantage of recent single crystal LaNiO 3 growth using the floating-zone method, we have measured the thermal expansion, the magnetostriction, and the pressure dependence of the magnetic susceptibility, which then allows derivation of the Grüneisen parameters γ e = $\frac{dlnN(E_F)}{d lnV}$, γ χ = $\frac{dlnχ}{d lnV}$, as well as of electric and thermal transport properties. We simulate the volume dependence of structural and magnetic properties using Density Functional Theory calculations at the Generalized Gradient Approximation level. A large discrepancy between experimental values and calculated ones suggests that strong correlations are likely to be dynamic in nature. This study also provides a side-by-side comparison of measurements in single crystal and polycrystalline samples of LaNiO 3 to elucidate intrinsic materials properties. A broad hump at high temperatures in the temperature dependence of magnetization found in the single crystal sample of LaNiO 3 has been rationalized by a model that includes the influence of electron correlations on the Landau diamagnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗