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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interplay between electron localization, magnetic order, and Jahn-Teller distortion dictates LiMnO2 phase stability

The development of manganese (Mn)-rich cathodes for Li-ion batteries promises to alleviate potential supply chain bottlenecks in battery manufacturing. Fundamental challenges in Mn-rich cathodes arise from phenomena such as structural changes due to cooperative Jahn-Teller (JT) distortions of in octahedral environments, Mn migration, and phase transformations to spinel-like order, all of which affect the electrochemical performance. These physically complex phenomena motivate an re-examination of the Li-Mn-O rock-salt space, with a focus on the thermodynamics of the prototypical, polymorphs. It is found that the generalized gradient approximation (GGA-PBEsol) and meta-GGA ( ) density functionals with empirically fitted on-site Hubbard corrections yield spurious stable phases for , such as predicting a phase with -like order ( ) to be the ground state instead of the orthorhombic (Pmmn) phase, which is the experimentally known ground state. Accounting for antiferromagnetic order in each structure is shown to have a substantial effect on the total energies and resulting phase stability. By using hybrid-GGA (HSE06) and GGA with self-consistent Hubbard parameters (on-site and inter-site ) calculated from linear response theory, the experimentally observed phase stability trends are recovered. The calculated on-site between Mn- states in the experimentally observed orthorhombic, layered, and spinel phases are significantly smaller than in and disordered layered structures, by within GGA. The smaller values of are shown to be correlated with a collinear ordering of JT distortions, in which all orbitals are oriented in the same direction. This cooperative JT effect can lead to greater electron delocalization from Mn along the states due to increased Mn-O covalency, which contributes to the greater electronic stability compared to the phases with noncollinear JT arrangements. The structures with collinear ordering of JT distortions also generate greater vibrational entropy, which helps stabilize these phases at high temperature. These phases are shown to be strongly insulating with large calculated band gaps , which are computed using HSE06 and .

Kam, Ronald L↗
DOE OSTI2021

Prediction and observation of intermodulation sidebands from anharmonic phonons in NaBr

A quantum Langevin model, like models from optomechanics, was developed for phonons. It predicts intermodulation phonon sidebands (IPSs) in anharmonic crystals. Ab initio calculations of anharmonic phonons in rock-salt NaBr showed these spectral features as many-body effects. Modern inelastic neutron scattering measurements on a crystal of NaBr at 300 K revealed diffuse intensity at high phonon energy from a predicted upper IPS. The transverse optical (TO) part of the new features originates from phonon intermodulation between the transverse acoustic (TA) and TO phonons. The longitudinal optical spectral features originate from three-phonon coupling between the TA modes and the TO lattice modes. The partner lower IPS proves to be an intrinsic localized mode. Interactions with the thermal bath broaden and redistribute the spectral weight of the IPS pair. These sidebands are a probe of the anharmonicity and quantum noise of phonons in NaBr and suggest novel interactions between photons and phonons.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Iridium valence variation and carrier sign tuning in ( Ca , Ba ) x La 2 – x CuIrO 6 double perovskites

Here, we report the structure and properties of ( Ca , Ba ) x La 2 – x CuIrO 6 . The rock-salt double perovskite structure goes through a P 1 ¯ to P 2 1 / n phase transition with increasing Ba content but not with Ca content. In both cases, the Ir ion is oxidized from 4 + to 5 + with increasing substitution. Transport and magnetic properties measurements reveal that all compositions are insulating with hysteretic spin-freezing magnetic behavior. Seebeck coefficient measurements reveal a large thermopower change from + 176 μ V /K in La 2 CuIrO 6 to – 223 μ V /K with increasing Ba content in Ba x La 2 – x CuIrO 6 . This behavior is modeled well by the Heikes formula for correlated hopping conduction. ( Ca , Ba ) x La 2 – x CuIrO 6 provides a model system for investigations of other systems with similar carrier sign tuning, with applications toward semiconductors and thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The effect of submicron grain size on thermal stability and mechanical properties of high-entropy carbide ceramics

(Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C high-entropy ceramics (HEC) with a submicron grain size of 400 to 600 nm were fabricated by spark plasma sintering using a two-step sintering process. Both X-ray and neutron diffractions confirmed the formation of single-phase with rock salt structure in the as-fabricated (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C samples. The effect of submicron grain size on the thermal stability and mechanical properties of HEC was investigated. The grain growth kinetics in the fine-grained HEC was small at 1300 and 1600°C, suggesting high thermal stability that was possibly related to the compositional complexity and sluggish diffusion in HEC. Compared to the coarse-grain HEC with a grain size of 16.5 µm, the bending strength and fracture toughness of fine-grained HEC were 25% and 20% higher respectively. The improvement of mechanical properties in fine-grained HEC may be attributed to micromechanistic mechanisms such as crack deflection.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Phase evolution during conventional and reactive flash sintering of (Mg,Ni,Co,Cu,Zn)O via in situ X-ray diffraction

Reactive flash sintering (RFS) enables the simultaneous synthesis and sintering of ceramics and has been shown to affect the reaction pathway of different materials. Herein, in situ synchrotron X-ray diffraction (XRD) is used to investigate the (Mg,Ni,Co,Cu,Zn)O entropy-stabilized oxide formation during: (i) conventional heating and (ii) RFS under current rate-controlled mode. The same reaction pathway is verified in both instances: the starting rock-salt (RS), spinel (Co 3 O 4 ), tenorite (CuO), and wurtzite (ZnO) phases transform into a single RS phase with a (1 1 1) to (2 0 0) intensity ratio of 0.67, consistent with a random distribution of the cations into the structure. Pt lattice peak shift from the XRD patterns is used as standard to monitor the sample surface temperature, revealing a strong endothermic reaction during the RS single-phase formation (Pt peaks shift toward higher angles while increasing sample temperature/current density). Furthermore, in RFS, the single-phase RS structure is formed in just 60 s at a furnace temperature of 600°C and a current rate of 220 mA mm -2 /min. Therefore, RFS greatly accelerates the synthesis of (Mg,Ni,Co,Cu,Zn)O, however, it does not play a role in the reaction pathway for this material formation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Targeted synthesis of predicted metastable compounds using modulated elemental reactants

Three metastable compounds predicted to be kinetically stable using an “island” approach were successfully synthesized from designed modulated elemental reactants. Fe0.8V0.2Se2 was synthesized by depositing ultrathin elemental layers in a V|Fe|Se sequence to control the local composition. An alloyed rock salt structured Pb3Mn2Se5 constituent layer, which does not exist as a bulk compound, was synthesized in the heterostructure (Pb3Mn2Se5)0.6VSe2 by depositing a precursor with a V|Se|Pb|Se|Mn|Se|Pb|Se|Mn|Se|Pb|Se sequence of elemental layers that mimicked the compositional profile of the targeted heterostructure. The heterostructure (PbSe)1+δ(FeSe2)2 was prepared by depositing a precursor with a repeating layering sequence of Fe|Pb|Fe|Se, where each sequence contains the number of atoms required to form a single unit cell. In all three systems, the local compositions in the layer sequence kinetically favored the nucleation and growth of the targeted products during the deposition. The diffusion lengths to form the targeted compounds were short, and the diffusion was limited by postdeposition low temperature annealing to favor the growth of the targeted compounds and avoid the decomposition into a mixture of thermodynamically stable compounds.

Lemon, Mellie (ORCID:0000000328705881)↗
DOE OSTI2024

Co-deposition of bismuth-nitrogen films on MgO (001) by molecular beam epitaxy

Here, we attempted to grow a thin film of BiN by co-deposition of bismuth and nitrogen on rock-salt structure MgO (001) substrates. Furthermore, we studied the effect of variation of the growth temperature and the nitrogen to bismuth flux ratios on sample growth. For the samples grown and conditions used, we do not find strong evidence for the formation of a bulk Bi-N alloy. Even for very high nitrogen to bismuth flux ratio, we observed only bismuth and no nitrogen using bulk Rutherford back-scattering spectroscopy measurements, and only 1%–2% nitrogen was seen through surface Auger electron spectroscopy measurements. The in-plane lattice measurements show that the resulting Bi (110) samples are strained, which is presumably caused by lattice mismatch between the sample and the substrate when grown without any buffer layer. The use of a high-temperature buffer layer helps to release strain in the sample but only along one axis. Measurements of the atomic layer spacing using x-ray diffraction and also scanning tunneling microscopy confirm the Bi (110) thin film sample structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Single-crystalline epitaxial TiO film: A metal and superconductor, similar to Ti metal

Titanium monoxide (TiO), an important member of the rock salt 3d transition-metal monoxides, has not been studied in the stoichiometric single-crystal form. It has been challenging to prepare stoichiometric TiO due to the highly reactive Ti 2+ . We adapt a closely lattice-matched MgO(001) substrate and report the successful growth of single-crystalline TiO(001) film using molecular beam epitaxy. This enables a first-time study of stoichiometric TiO thin films, showing that TiO is metal but in proximity to Mott insulating state. We observe a transition to the superconducting phase below 0.5 K close to that of Ti metal. Density functional theory (DFT) and a DFT-based tight-binding model demonstrate the extreme importance of direct Ti–Ti bonding in TiO, suggesting that similar superconductivity exists in TiO and Ti metal. Our work introduces the new concept that TiO behaves more similar to its metal counterpart, distinguishing it from other 3d transition-metal monoxides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Design Principles to Govern Electrode Fabrication for the Lithium Trivanadate Cathode

A full depth of discharge mathematical model for the lithium trivanadate cathode, considering lithiation of the layered α-phase, phase change, and lithiation of the rock-salt like β-phase at lower potentials, is developed. The coupled electrode-scale and crystal-scale model is fit to electrochemical data, and additionally validated with operando EDXRD. There is good agreement between the simulated and measured spatial variation of the volume fraction of the β-phase. This mathematical model is used to guide electrode fabrication, accounting for both ionic and electronic transport effects. Values of three design parameters—electrode thickness, porosity, and volume fraction of conductor—are identified, and the sensitivity of the energy density to these design parameters is quantified. The model is also used to investigate electrode design to create electrodes that deliver the maximum achievable energy density under the constraint that the α to β-phase transition is avoided, since phase change has been demonstrated to reduce cycle life. The energy density sacrificed to avoid phase change decreases at higher discharge rates, but the target values for electrode fabrication remain the same as those when optimizing the electrode for the full depth of discharge.

25 ENERGY STORAGE↗
DOE OSTI2024

Impact of Electrolyte Additives on the Lifetime of High Voltage NMC Lithium-Ion Pouch Cells

This work involves improving the lifetime of lithium-ion cells during high voltage cycling using electrolyte additives. Three generations of electrolyte additives were investigated and screened in NMC442/graphite pouch cells using a 24 h voltage-hold protocol at 40 degrees C to accelerate oxidative reactions occurring at 4.4 V. Once promising additives and combinations were identified, they were then tested in cobalt-free NMC640/graphite cells for long-term cycling to upper cutoff voltages of 4.3, 4.4, and 4.5 V at temperatures of 20, 40, and 55 degrees C. Degradation mechanisms were probed using dV/dQ analysis, micro-X-ray fluorescence spectroscopy, and electrochemical impedance spectroscopy. The primary failure mode of cells held at high voltages is due to increase in cell impedance, which is correlated to the dissolution of transition metals, specifically manganese, originating from the positive electrode. We believe this dissolution is presumably due to the formation of a high impedance rock salt surface layer on the NMC positive electrode particles. Such deleterious outcomes can be limited by selecting an appropriate electrolyte additive package. It is hoped that this paper can provide a starting point for developing NMC Li-ion cells that can operate to voltages as high as 4.4 V and still display long lifetimes.

Azam, Saad↗
DOE OSTI2025

The Sensitivity of Nickel Substitution in the Structural Design of Manganese-Based Layered and Lithiated Spinel Electrodes for Li-Ion Batteries

A concerted effort is being made at Argonne National Laboratory to explore and develop high-performance lithium-manganese-nickel-oxide cathode materials for the lithium battery industry. They are both energy- and cost-competitive relative to cobalt- and nickel-rich systems, such as LiCoO 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , and LiNi 0.8 Mn 0.1 Co 0.1 O 2 . The recent discovery of the structural versatility of LiNi 0.5 Mn 0.5 O 2 , has revealed that it can exist in three configurations: lithiated spinel, partially disordered layered, and completely disordered rock salt within a common cubic-close-packed oxygen array. This versatility opens up the possibility of designing structurally integrated electrode components with interlinking 2-D (layered) and 3-D (spinel) channels for Li-ion transport. This paper highlights the sensitivity of Ni substitution and synthesis temperature on the structural and electrochemical properties of LiNi 0.50 Mn 0.50 O 2 , LiNi 0.53 Mn 0.47 O 2 , LiNi 0.47 Mn 0.53 O 2 , and LiNi 0.25 Mn 0.75 O 2 electrodes, as well as a cobalt-containing composition, LiNi 0.333 Mn 0.333 Co 0.333 O 2 , when synthesized at a relatively low temperature of 400 °C.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on CrO by Materials Project

CrO is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cr2+ is bonded to six equivalent O2- atoms to form a mixture of corner and edge-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Cr–O bond lengths are 2.23 Å. O2- is bonded to six equivalent Cr2+ atoms to form a mixture of corner and edge-sharing OCr6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrO by Materials Project

SrO is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing SrO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Sr–O bond lengths are 2.60 Å. O2- is bonded to six equivalent Sr2+ atoms to form a mixture of edge and corner-sharing OSr6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaTe by Materials Project

BaTe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent Te2- atoms to form a mixture of edge and corner-sharing BaTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Ba–Te bond lengths are 3.54 Å. Te2- is bonded to six equivalent Ba2+ atoms to form a mixture of edge and corner-sharing TeBa6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ScC by Materials Project

ScC is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sc3+ is bonded to six equivalent C3- atoms to form a mixture of corner and edge-sharing ScC6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Sc–C bond lengths are 2.34 Å. C3- is bonded to six equivalent Sc3+ atoms to form a mixture of corner and edge-sharing CSc6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TeAs by Materials Project

AsTe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. As2+ is bonded to six equivalent Te2- atoms to form a mixture of corner and edge-sharing AsTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All As–Te bond lengths are 2.97 Å. Te2- is bonded to six equivalent As2+ atoms to form a mixture of corner and edge-sharing TeAs6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZrAs by Materials Project

ZrAs is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Zr3+ is bonded to six equivalent As3- atoms to form a mixture of edge and corner-sharing ZrAs6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Zr–As bond lengths are 2.74 Å. As3- is bonded to six equivalent Zr3+ atoms to form a mixture of edge and corner-sharing AsZr6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DySb by Materials Project

DySb is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Dy3+ is bonded to six equivalent Sb3- atoms to form a mixture of corner and edge-sharing DySb6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Dy–Sb bond lengths are 3.10 Å. Sb3- is bonded to six equivalent Dy3+ atoms to form a mixture of corner and edge-sharing SbDy6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗