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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Distribution of rare earth and other critical elements in lignites from the Eocene Jackson Group, Texas

Coal is increasingly evaluated as a source of rare earth elements (REEs) in the United States to address the overreliance on imported REEs. The objective of this study was to assess the distribution of REEs in lignites from selected mining areas in the Texas Gulf Coastal Plain region. Thirty-one archived lignite and rock samples previously collected by the U.S. Geological Survey were analyzed for their rare earth element and critical mineral content. These include samples from one core (5400 and 5500 lignite horizons) and two opencast lignite mines (Gibbons Creek 3500 and 4500 horizons, and San Miguel horizons A to D) in the Eocene Jackson Group of the Texas Gulf of Mexico Coastal Plain. Some lithologies in the Gibbons Creek 3500 and 4500 lignite-bearing sections have high total rare earth, yttrium (Y), and scandium (Sc) (REYSc) values, up to 7800 ppm (ash basis) REYSc. The lignite lithologies show an enrichment in rare earths, [samarium (Sm) through gadolinium (Gd)]. The basal Gibbons Creek 3500 lignite bench shows a heavy rare earth element enrichment pattern resembling that often seen in peats through high volatile A bituminous coals. The 5500 lignite sequence, overlying the latter lignite sections, shows a light rare earth enrichment. The San Miguel lignite benches have heavy rare earth enrichments with a negative europium (Eu) anomaly.

58 GEOSCIENCES↗
DOE OSTI2022

Assessing Mg–Sc–(rare earth) ternary phase stability via constituent binary cluster expansions

The disordered Mg–Sc body-centered cubic (bcc) phase is both lightweight and strong; however, the system is impractical for general industrial use due to the high cost of scandium. Here we propose a computationally efficient metric that assesses ternary rare earth element additions that may stabilize the bcc phase at lower Sc concentrations. We find that the bcc phase is stabilized by the ternary addition of Y or Er, but not by La, Ce, or Nd, and we validate these predictions by experimental production and characterization of Mg–Sc–(Y,Er,Nd) alloys. The results suggest a computationally efficient method to anticipate integration of ternary elements into binary systems using cluster expansions of constituent binaries.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Solute diffusion behavior during heat treatment and its impact in Sc-microalloyed Al-Cu system

Scandium (Sc) is a promising microalloying element that enhances the strength and thermal stability of aluminum (Al) alloys. However, these benefits are not fully realized in aluminum-copper (Al-Cu) systems, and corrosion resistance often declines due to the complex phase evolution and diffusion behavior of Cu and Sc. Here, to clarify this, solute diffusion behavior and Cu-Sc interaction during heat treatment (HT) were investigated using in situ synchrotron-based transmission x-ray microscopy (TXM), wide-angle x-ray scattering (WAXS), and x-ray absorption near-edge structure (XANES) spectroscopy. The results, supported by electron microscopy, reveal strong Cu-Sc bonding that significantly impedes solute diffusion, leading to inhomogeneous solute distribution and non-uniform precipitation. Moreover, the Al-Cu-Sc eutectic phase exhibits high thermal stability, resisting dissolution even near the matrix liquidus. These findings quantitatively elucidate the sluggish diffusion kinetics of Cu and Sc, which can help redesign HT schedules to improve both mechanical properties and corrosion resistance in Sc-microalloyed Al-Cu alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hydrated doped-BaZrO 3 proton conductors studied by positron annihilation lifetime spectroscopy

The study of defect chemistry for doped BaZrO 3 proton conductors is of particular interest because of defect interactions that can affect the proton conductivity of the material. Protons incorporated due to the material's hydration can be trapped by negatively charged immobile dopants, reducing proton mobility. The reduction of the proton conduction impedes using BaZrO 3 materials in energy conversion applications at intermediate temperatures (300°C – 600°C). The probing of proton trapping in doped BaZrO 3 is hindered by the limited availability of techniques sensitive to defect chemistries. In this work, we used positron annihilation lifetime spectroscopy (PALS) to study the defect chemistry of Y-doped and Sc-doped BaZrO 3 . Using a two-state positron trapping model we showed that PALS can be used to study the defect chemistry of hydrated dense proton conductors. Positron trapping rates and lifetimes were correlated with doping levels of the materials. Probability significance t-tests were carried out for PALS parameters to verify whether there are differences/similarities for various populations: non-doped/doped, level and type of doping, high temperature, and surface effects. Further, the results revealed that the initial doping generates a significant number of traps available for positrons. Doping in yttrium increased the positron trapping rate, while this effect was not observed with scandium. Low-temperature hydration affects specimens significantly inhibiting positron trapping at undoped BaZrO 3 material and highly doped specimens. Positronium formation in rough surface layers, and highly doped specimens was detected but does not exceed 1%.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ligand–Metal Complementarity in Rare-Earth and Actinide Chemistry

In this article, the rare-earths are comprised of scandium, yttrium, and the lanthanides (atomic numbers 21, 39, and 57–71). (1) While these elements are essential to modern life, they were historically characterized as simple, perhaps dull, compared to the rich multielectron chemistry of d-block metals in catalysts and enzymes. These descriptions were quite fair and largely true at the time that these elements were being discovered and the first compounds containing them were being synthesized, although much progress has been made to overturn this view of the rare earths. Similarly, discussions about actinide chemistry are sometimes limited to research pertinent to the nuclear industry, which, while comprising technologies vital to modern society, does not celebrate the fascinating chemical space that much of the actinide series occupies. These historic characterizations of most of the rare-earth and actinide elements persist in some textbooks, and we acknowledge that it is a helpful place to start; however, altogether these series comprise 32 elements-27% of the 118 known by 2024-and we suggest it would be an unfortunate twist of physics if such a large proportion of the Periodic Table were genuinely dull. Indeed, as this Inorganic Chemistry Forum Issue “Ligand-Metal Complementarity in Rare-Earth and Actinide Chemistry” highlights, the chemistry-let alone the physics, that is, spectroscopy and magnetism-of these elements is rich and depends on ligands!

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

Investigating the Theranostic Potential of Elementally Matched [ 43 Sc]Sc-PSMA-617 and [ 47 Sc]Sc-PSMA-617

The theranostic approach, which employs diagnostic radiopharmaceuticals to select patients who would benefit from targeted radiotherapy agents, has become an invaluable strategy for effective medical care. Scandium radionuclides offer the advantage of forming elementally matched and chemically identical diagnostic and therapeutic compounds, making them ideal candidates for this strategy. PSMA-617 is an established prostate-specific membrane antigen targeting agent and can be used as a proof of concept to investigate 43 Sc, the diagnostic nuclide, and 47 Sc, the therapeutic nuclide, as a theranostic pair. Methods: Cellular uptake, competitive binding assays, and internalization studies were carried out using LNCaP or PC-3 cell lines. [ 43 Sc]Sc-PSMA-617 was used in PET imaging studies in LNCaP or PC-3 tumor models, with time points ranging from 1–9 h. LNCaP tumor-bearing mice injected with [ 47 Sc]Sc-PSMA-617 were imaged using SPECT up to 48 h. A longitudinal study was carried out using LNCaP tumor-bearing mice imaged with [ 43 Sc]Sc-PSMA-617 prior to receiving a therapeutic dose of [ 47 Sc]Sc-PSMA-617. Results: 43 Sc and 47 Sc were incorporated into PSMA-617 at radiochemical yields of >99%. Cellular uptake studies demonstrated high uptake and specificity to PSMA receptors for [ 47 Sc]Sc-PSMA-617. In vivo PET studies showed specificity of [ 43 Sc]Sc-PSMA-617 while SPECT studies demonstrated tumor retention of [ 47 Sc]Sc-PSMA-617 up to 48 h. [ 47 Sc]Sc-PSMA-617 demonstrated therapeutic efficacy by delaying tumor growth and increasing survival rates from a single administered dose in xenograft models. More importantly, the PET results from [ 43 Sc]Sc-PSMA-617 PET were highly correlated with the therapeutic response from [ 47 Sc]Sc-PSMA-617, showing that 43 Sc PET data can predict therapeutic outcomes in individual animals from 47 Sc agents, even in animals sharing a genetic background and implanted with tumors from the same cell line. Conclusions: Two chemically identical, PSMA-targeting radioscandium pharmaceuticals demonstrated in vivo stability, specificity and retention in PSMA+ tumor models. A theranostic study showed that a higher 43 Sc PET SUVmean was strongly correlated to therapeutic response from the 47 Sc agent, demonstrating that 43 Sc and 47 Sc can be used as an elementally matched theranostic pair.

Biodistribution↗
DOE OSTI2022

Crystal Chemistry and Thermodynamics of HREE (Er, Yb) Mixing in a Xenotime Solid Solution

Rare earth elements (REEs), the 15 naturally occurring lanthanides plus yttrium and scandium, are ubiquitously used in modern life as they are critical components of many advanced devices and technologies. However, the demand for REEs is not equal, with the heavy rare earth elements (HREEs) having a higher demand. Xenotime (HREEPO 4 ) is an important HREE ore mineral and globally is an economical source of HREE. Most of the crystallographic and thermodynamic properties of xenotime endmembers have been elucidated by calorimetric, solubility, and high-pressure studies. Yet, in natural systems, endmembers are rarely encountered, and instead, REE solid solutions are more commonly observed. Here, we characterize the crystal chemistry, thermodynamics of HREE mixing, and high-temperature material behaviors and thermochemistry of a synthetic erbium (Er)-ytterbium (Yb) binary xenotime solid solution (Er (x) Yb (1-x) PO 4 ) using a suite of experimental techniques, including X-ray fluorescence spectroscopy, synchrotron X-ray powder diffraction implemented with Rietveld analysis, Fourier transform infrared spectroscopy coupled with attenuated total reflectance, Raman spectroscopy, thermogravimetric analysis coupled with differential scanning calorimetry, and high-temperature oxide melt drop solution calorimetry. Our results shed light on the formation of natural xenotimes and lay the foundation for their industrial applications as thermal coating materials.

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

Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei

Strong interactions preserve an approximate isospin symmetry between up (u) and down (d) quarks, part of the more general flavor symmetry. In the case of K meson production, if this isospin symmetry were exact, it would result in equal numbers of charged (K + and K − ) and neutral (K 0 and ${\overline{K}}^{0}$) mesons produced in collisions of isospin-symmetric atomic nuclei. Here, we report results on the relative abundance of charged over neutral K meson production in argon and scandium nuclei collisions at a center-of-mass energy of 11.9 GeV per nucleon pair. We find that the production of K + and K − mesons at mid-rapidity is (18.4 ± 6.1)% higher than that of the neutral K mesons. Although with large uncertainties, earlier data on nucleus-nucleus collisions in the collision center-of-mass energy range $2.6 \, < \, \sqrt{{s}_{NN}} \, < \, 200$ GeV are consistent with the present result. Using well-established models for hadron production, we demonstrate that known isospin-symmetry breaking effects and the initial nuclei containing more neutrons than protons lead only to a small (few percent) deviation of the charged-to-neutral kaon ratio from unity at high energies. Thus, they cannot explain the measurements. The significance of the flavor-symmetry violation beyond the known effects is 4.7σ when the compilation of world data with uncertainties quoted by the experiments is used. New systematic, high-precision measurements and theoretical efforts are needed to establish the origin of the observed large isospin-symmetry breaking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Heat-resistant aluminium alloys

Scandium added to Al–Cu–Mg–Ag alloys leads to an in situ phase transformation of coherent Cu-rich nanoprecipitates at elevated temperature, with Sc atoms diffusing and occupying their interstitial sites. Notably, the transformed nanoprecipitates have enhanced thermal stability while maintaining a large volume fraction and these two microstructural features enable high tensile strength of the Al alloy with creep resistance up to 400 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-throughput screening for discovery of benchtop separations systems for selected rare earth elements

Abstract Rare earth (RE) elements (scandium, yttrium, and the lanthanides) are critical for their role in sustainable energy technologies. Problems with their supply chain have motivated research to improve separations methods to recycle these elements from end of life technology. Toward this goal, we report the synthesis and characterization of the ligand tris[(1-hydroxy-2-oxo-1,2-dihydropyridine-3-carboxamido)ethyl]amine, H 3 1·TFA (TFA = trifluoroacetic acid), and complexes 1·RE (RE = La, Nd, Dy). A high-throughput experimentation (HTE) screen was developed to quantitatively determine the precipitation of 1·RE as a function of pH as well as equivalents of H 3 1·TFA. This method rapidly determines optimal conditions for the separation of RE mixtures, while minimizing materials consumption. The HTE-predicted conditions are used to achieve the lab-scale separation of Nd/Dy ( SF Nd/Dy = 213 ± 34) and La/Nd ( SF La/Nd = 16.2 ± 0.2) mixtures in acidic aqueous media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Observing the three-dimensional dynamics of supported metal complexes

Dynamics are intricately linked with activity and selectivity when it comes to catalysis, as noted for instance in the enzymatic principles of induced fit and allostery, and yet the range of motions heterogeneous catalytic sites are able to undergo is poorly understood. Solid-state nuclear magnetic resonance (NMR) spectroscopy is perhaps the only tool capable of probing the rapid conformational dynamics found in heterogeneous catalysts but has historically been restricted by its low sensitivity, limiting the detail with which structures can be resolved. In this work, we apply solid-state NMR and dynamic nuclear polarization, in combination with density functional theory modeling, to reveal the high-resolution structure and motional freedom of a scandium supported complex in three dimensions. The results are contrasted with the study of the analogous homoleptic complex in the crystalline state, highlighting the impacts that surface structure may have on the dynamics of supported complexes.

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

Al 0.68 Sc 0.32 N Lamb wave resonators with electromechanical coupling coefficients near 10.28%

Aluminum scandium nitride (Al 1-x Sc x N/AlScN) (x = 0.32) Lamb wave resonators (LWR) have been fabricated and tested to demonstrate electromechanical coupling coefficients (k t 2 ) in excess of 10%. The resonators exhibited an average k t 2 and unloaded quality factor (Q u ) of 10.28% and 711, respectively, when calculated from the measured data. Applying the Butterworth Van-Dyke (BVD) model to the measured data enabled the extraction of the resonator's lumped element parameters to calculate the motional quality factor (Q m ), which neglects the contributions of the electrical traces. For the best measured resonator response, results from the BVD model showed a Q m of 1184 and a resulting figure-of-merit (FOM = K 2 ·Q m ) of 100. Comparing the response of similar AlScN and AlN resonators shows that the AlScN LWR has a significantly lower motional resistance (R m ), suggesting that AlScN has a strong potential for use in piezoelectric microelectromechanical oscillators.

42 ENGINEERING↗
DOE OSTI2022

Lattice and electronic structure of ScN observed by angle-resolved photoemission spectroscopy measurements

Scandium nitride (ScN) has recently attracted much attention for its potential applications in thermoelectric energy conversion, as a semiconductor in epitaxial metal/semiconductor superlattices, as a substrate for GaN growth, and alloying it with AlN for 5G technology. This study was undertaken to better understand its stoichiometry and electronic structure. ScN (100) single crystals 2 mm thick were grown on a single crystal tungsten (100) substrate by a physical vapor transport method over a temperature range of 1900–2000 °C and a pressure of 20 Torr. The core level spectra of Sc 2p 3/2,1/2 and N 1s were obtained by x-ray photoelectron spectroscopy (XPS). The XPS core levels were shifted by 1.1 eV toward higher values as the [Sc]:[N] ratio varied from 1.4 at 1900 °C to ~1.0 at 2000 °C due to the higher binding energies in stoichiometric ScN. Angle-resolved photoemission spectroscopy measurements confirmed that ScN has an indirect bandgap of ~1.2 eV.

42 ENGINEERING↗
DOE OSTI2023

Sub-quarter micrometer periodically poled Al 0.68 Sc 0.32 N for ultra-wideband photonics and acoustic devices

In this study, we demonstrate the ability of polarity inversion of sputtered aluminum scandium nitride thin films through post-fabrication processes with domain widths as small as 220 nm at a periodicity of 440 nm. An approach using photo- and electron-beam lithography to generate sub-quarter micrometer feature size with adjustable duty cycle through a lift-off process is presented. Here, the film with a coercive field $E_c^+$ of 5.35 MV/cm was exercised first with a 1 kHz triangular double bipolar wave and ultimately poled with a 0.5 kHz double monopolar wave using a Radiant Precision Premier II tester. The metal polar (M-polar) and nitrogen polar (N-polar) domains were identified and characterized through potassium hydroxide wet etching as well as piezoresponse force microscopy (PFM). Well-distinguished boundaries between the oppositely polarized domain regions were confirmed through the phase diagram of the PFM results. The relationship between the electrode width, poling voltage, and domain growth was experimentally studied and statistically analyzed, where 7.96 nm/V domain width broadening vs escalating poling voltage was observed. This method produces extremely high domain spatial resolution in III-nitride materials via poling and is transferable to a CMOS-compatible photolithography process. The spatial resolution of the periodically poled Al 0.68 Sc 0.32 N is suitable for second-harmonic generation of deep ultraviolet through quasi-phase-matching and RF MEMS operating in the X-Band spectrum.

36 MATERIALS SCIENCE↗
DOE OSTI2024

S-band acoustoelectric amplifier in an InGaAs-AlScN-SiC architecture

Here, we report on an acoustoelectric slab waveguide heterostructure for phonon amplification using a thin Al 0.58 Sc 0.42 N film grown directly on a 4H-SiC substrate with an ultra-thin In 0.53 Ga 0.47 As epitaxial film heterogeneously integrated onto the surface of the Al 0.58 Sc 0.42 N. The aluminum scandium nitride film grown directly on silicon carbide enables a thin (∼850 nm thick) piezoelectric film to be deposited on a thermally conductive bulk substrate (370 W/m K for 4H-SiC); the high thermal conductivity of the substrate, large mobility of the semiconductor (∼7000 cm 2 /V s), and low carrier concentration (∼5 × 10 15 cm −3 ) yield low self-heating. A Sezawa mode with optimal overlap between the peak of its evanescent electric field and the semiconductor charge carriers is supported. The high velocity of the heterostructure materials allows us to operate the Sezawa mode amplifier at 3.05 GHz, demonstrating a gain of 500 dB/cm (40 dB in 800 μm). Additionally, a terminal end-to-end radio frequency gain of 7.7 dB and a nonreciprocal transmission of 52.6 dB are achieved with a dissipated DC power of 2.3 mW. In conclusion, the power added efficiency and acoustic noise figure are also characterized.

Hackett, L.↗
DOE OSTI2026

Domain-wall-mediated polarization switching in ferroelectric AlScN: Strain relief and field-dependent dynamics

While scandium-doped aluminum nitride (AlScN) exhibits robust ferroelectricity and excellent thermal stability, its utility is limited by an exceptionally high coercive field (𝐸 𝑐 ) for polarization switching. Unraveling the atomistic switching dynamics is therefore critical for tailoring 𝐸 𝑐 . Here, in this study, we combine density functional theory and machine-learning molecular dynamics to elucidate the polarization switching mechanisms in AlScN over various Sc concentrations and applied electric fields. We find that excessive lattice strain strictly prohibits collective polarization switching, but the preexisting domain walls relieve strain and lead to a distinct switching dynamics—dictating a field-dependent switching mechanism. At low electric fields, switching occurs via gradual domain-wall propagation consistent with the Kolmogorov-Avrami-Ishibashi model. In contrast, high fields stimulate additional nucleation, driving a rapid, homogeneous reversal process described by the simultaneous nonlinear nucleation and growth model. These findings highlight the critical role of domain-wall dynamics and suggest domain engineering as a viable strategy to tailor coercive fields in AlScN and related ferroelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Aluminum Boron Nitride Ferroelectric Field-Effect Transistors With ZnO Semiconductor Channel

The discovery of ferroelectricity in hafnium zirconium oxide (HfxZr 1−x O2) and related fluorite materials has spurred interest in ferroelectric devices suitable for integration with silicon integrated circuits (ICs), especially those that can be embedded in the back-end-of-line (BEOL) process. More recently, ferroelectricity has been found in wurtzite aluminum nitride-based materials, such as scandium and boron-doped aluminum nitride (Al 1−x ScxN and Al 1−x BxN). Although these materials currently have undesirably large coercive electric fields, and small breakdown electric field-to-coercive electric field ratio, their low processing temperatures and large remanent polarization offer intriguing possibilities for device applications. Furthermore, we report ferroelectric field-effect transistors (FeFETs) with a 15 nm thick Al0.88B0.12N layer and an 11 nm ZnO semiconductor channel, achieving a memory window >1 V and switching voltages ( V switch ) <±10 V.

42 ENGINEERING↗
DOE OSTI2023

Trivalent rare earth metal cofactors confer rapid NP-DNA polymerase activity

Here, a DNA polymerase with a single mutation and a divalent calcium cofactor catalyzes the synthesis of unnatural N3'→P5' phosphoramidate (NP) bonds to form NP-DNA. However, this template-directed phosphoryl transfer activity remains orders of magnitude slower than native phosphodiester synthesis. Here, we used time-resolved x-ray crystallography to show that NP-DNA synthesis proceeds with a single detectable calcium ion in the active site. Using insights from isotopic and elemental effects, we propose that one-metal-ion electrophilic substrate activation is inferior to the native two-metal-ion mechanism. We found that this deficiency in divalent activation could be ameliorated by trivalent rare earth and post–transition metal cations, substantially enhancing NP-DNA synthesis. Scandium(III), in particular, confers highly specific NP activity with kinetics enhanced by more than 100-fold over calcium(II), yielding NP-DNA strands up to 100 nucleotides in length.

59 BASIC BIOLOGICAL SCIENCES↗