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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on La(SiPt)2 by Materials Project

LaPt2Si2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. La2+ is bonded in a 8-coordinate geometry to eight Si4- atoms. There are four shorter (3.25 Å) and four longer (3.30 Å) La–Si bond lengths. There are two inequivalent Pt3+ sites. In the first Pt3+ site, Pt3+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing PtSi4 tetrahedra. All Pt–Si bond lengths are 2.52 Å. In the second Pt3+ site, Pt3+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are four shorter (2.47 Å) and one longer (2.48 Å) Pt–Si bond lengths. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 4-coordinate geometry to four equivalent La2+ and four equivalent Pt3+ atoms. In the second Si4- site, Si4- is bonded in a 5-coordinate geometry to four equivalent La2+ and five Pt3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(Co2B)6 by Materials Project

LaCo12B6 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. La3+ is bonded in a hexagonal planar geometry to six equivalent B3- atoms. All La–B bond lengths are 3.09 Å. There are two inequivalent Co+1.25+ sites. In the first Co+1.25+ site, Co+1.25+ is bonded in a T-shaped geometry to three equivalent B3- atoms. There are two shorter (2.09 Å) and one longer (2.11 Å) Co–B bond lengths. In the second Co+1.25+ site, Co+1.25+ is bonded to four equivalent B3- atoms to form a mixture of distorted corner and edge-sharing CoB4 trigonal pyramids. There are two shorter (2.04 Å) and two longer (2.05 Å) Co–B bond lengths. B3- is bonded in a 7-coordinate geometry to one La3+ and seven Co+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(Sb3Ru)4 by Materials Project

LaRu4Sb12 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. La3+ is bonded to twelve equivalent Sb1- atoms to form LaSb12 cuboctahedra that share faces with eight equivalent RuSb6 octahedra. All La–Sb bond lengths are 3.52 Å. Ru+2.25+ is bonded to six equivalent Sb1- atoms to form RuSb6 octahedra that share corners with six equivalent RuSb6 octahedra and faces with two equivalent LaSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 54°. All Ru–Sb bond lengths are 2.64 Å. Sb1- is bonded in a 2-coordinate geometry to one La3+, two equivalent Ru+2.25+, and two equivalent Sb1- atoms. There are one shorter (2.98 Å) and one longer (3.01 Å) Sb–Sb bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(Mo3S4)2 by Materials Project

LaMo6S8 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. La3+ is bonded in a body-centered cubic geometry to eight S2- atoms. There are two shorter (2.83 Å) and six longer (3.06 Å) La–S bond lengths. Mo+2.17+ is bonded to five S2- atoms to form a mixture of edge and corner-sharing MoS5 square pyramids. There are a spread of Mo–S bond distances ranging from 2.41–2.62 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one La3+ and three equivalent Mo+2.17+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to one La3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(Tl3Te2)3 by Materials Project

Tl9LaTe6 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. La3+ is bonded to six Te2- atoms to form LaTe6 octahedra that share corners with six equivalent TlTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–39°. There are two shorter (3.25 Å) and four longer (3.28 Å) La–Te bond lengths. There are two inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 5-coordinate geometry to five Te2- atoms. There are a spread of Tl–Te bond distances ranging from 3.26–3.72 Å. In the second Tl1+ site, Tl1+ is bonded to six Te2- atoms to form TlTe6 octahedra that share corners with six equivalent LaTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–39°. There are four shorter (3.51 Å) and two longer (3.56 Å) Tl–Te bond lengths. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 8-coordinate geometry to one La3+ and seven Tl1+ atoms. In the second Te2- site, Te2- is bonded in a 1-coordinate geometry to one La3+ and nine Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si) 13 -Based Compounds

The transition toward a carbon-neutral society based on renewable energies goes hand in hand with the availability of energy-efficient technologies. Here, magnetocaloric cooling is a very promising refrigeration technology to fulfill this role regarding cryogenic gas liquefaction. However, the current reliance on highly resource critical, heavy rare-earth-based compounds as magnetocaloric material makes global usage unsustainable. Here, we aim to mitigate this limitation through the utilization of a multicaloric cooling concept, which uses the external stimuli of isotropic pressure and magnetic field to tailor and induce magnetostructural phase transitions associated with large caloric effects. In this study, La 0.7 Ce 0.3 Fe 11.6 Si 1.4 is used as a nontoxic, low-cost, low-criticality multiferroic material to explore the potential, challenges, and peculiarities of multicaloric cryocooling, achieving maximum isothermal entropy changes up to −28 J (kg K) −1 in the temperature range from 190 K down to 30 K. Thus, the multicaloric cooling approach offers an additional degree of freedom to tailor the phase transition properties and may lead to energy-efficient and environmentally friendly gas liquefaction based on designed-for-purpose, noncritical multiferroic materials.

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

Resonant Soft X-Ray Scattering from Stripe-Ordered La 2 - x Ba x Cu O 4 Detected by a Transition-Edge Sensor Array Detector

Resonant soft x-ray scattering (RSXS) is a leading probe of valence-band order in materials best known for detecting charge-density-wave order in copper-oxide superconductors. One of the biggest limitations on the RSXS technique is the presence of a severe fluorescence background, which, like the RSXS cross section itself, is enhanced under resonant conditions. This background prevents the study of weak signals such as diffuse scattering from glassy or fluctuating order that is spread widely over momentum space. Recent advances in superconducting transition-edge-sensor (TES) detectors have led to major improvements in energy resolution and detection efficiency in the soft x-ray range. Here, we perform a RSXS study of stripe-ordered La 2 - x Ba x Cu O 4 at the Cu L 3 / 2 edge (932.2 eV) using a TES detector with 1.5-eV resolution, to evaluate its utility for mitigating the fluorescence-background problem. We find that, for suitable degree of detuning from the resonance, the TES rejects the fluorescence background, leading to a five to ten times improvement in the statistical quality of the data compared to an equivalent, energy-integrated measurement. We conclude that a TES introduces a promising method to reducing background in RSXS studies and may lead to discoveries in materials exhibiting valence-band order that is fluctuating or glassy.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Digitizing Curves from LA-10860 to be Used in CritView

This report documents the digitization of figures from LA-10860-MS in order to import the data into the CritView software application. The original figures were created by Los Alamos National Laboratory and the latest revision was released in 1986. All figures were digitized using Engauge Digitizer (ver. 12.1) .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Initial Site-Specific De-Inventory Report for La Crosse

This report addresses the tasks, equipment, and interfaces necessary for the complete de-inventory of the La Crosse Boiling Water Reactor (LACBWR) independent spent fuel storage installation (ISFSI) site.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

ORNL FY2024 Nuclear Data Evaluation Contributions: Cu, La, N, and Ta [Slides]

63,65 Cu angular distributions resolved for ENDF/B-VIII.1, consistent with both differential data and integral benchmark performance. 139 La RRR and URR evaluations will be merged with the LANL high energy evaluation, and to be submitted to the future ENDF-B release (post-VIII.1). 14 N RRR evaluation is planned to produce n+ 14 N, p+ 14 C, and a+ 11 B contributions to be submitted to the future ENDF-B release (post-VIII.1). 181 Ta covariances repaired and reported as intended in an errata to ENDF/B-VIII.1.

139-La↗
NASA NTRS2014

High-Precision Measurement of Eu/Eu* in Geological Glasses via LA-ICP-MS Analysis

Elemental fractionation during laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis has been historically documented between refractory and volatile elements. In this work, however, we observed fractionation between light rare earth elements (LREEs) and heavy rare earth elements (HREEs) when using ablation strategies involving large spot sizes (greater than 100 millimeters) and line scanning mode. In addition: (1) ion yields decrease when using spot sizes above 100 millimeters; (2) (Eu/Eu*)(sub raw) (i.e. Europium anomaly) positively correlates with carrier gas (He) flow rate, which provides control over the particle size distribution of the aerosol reaching the ICP; (3) (Eu/Eu*)(sub raw) shows a positive correlation with spot size, and (4) the changes in REE signal intensity, induced by the He flow rate change, roughly correlate with REE condensation temperatures. The REE fractionation is likely driven by the slight but significant difference in their condensation temperatures. Large particles may not be completely dissociated in the ICP and result in preferential evaporation of the less refractory LREEs and thus non-stoichiometric particle-ion conversion. This mechanism may also be responsible for Sm-Eu-Gd fractionation as Eu is less refractory than Sm and Gd. The extent of fractionation depends upon the particle size distribution of the aerosol, which in turn is influenced by the laser parameters and matrix. Ablation pits and lines defined by low aspect ratios produce a higher proportion of large particles than high aspect ratio ablation, as confirmed by measurements of particle size distribution in the laser induced aerosol. Therefore, low aspect ratio ablation introduces particles that cannot be decomposed and/or atomized by the ICP and thus results in exacerbated elemental fractionation. Accurate quantification of REE concentrations and Eu/Eu* requires reduction of large particle production during laser ablation. For the reference materials analyzed in this work, the 100 millimeters spot measurements of Eu/Eu* agreed with GeoRem preferred values within 3 percent. Our long-term analyses of Eu/Eu* in MPI-DING glass KL-2G and USGS glass BIR-1G were reproducible at 3 percent (2 RSD).

geological glasses↗
NASA NTRS2024

Characterizing the 2019-2021 Drought in La Plata River Basin With GLDAS and SMAP

Study region The La Plata River Basin (LPRB) is an area of interest, as there was a significant drought event from 2019 to 2021. With the LPRB being the second largest river basin in South America, this drought affected all aspects of life for over 100 million people who inhabit this area. Study focus In this study, we utilized satellite and model datasets to examine spatial and temporal variability of hydrological anomalies throughout the basin before and during the drought event. These variable anomalies, such as precipitation and groundwater, are derived from the Global Land Data Assimilation System (GLDAS). Additionally, the Soil Moisture Active Passive (SMAP) observations were used in the spatial and temporal analysis of the drought. The water loss was calculated using the Mann-Kendall test to assess the changes in anomalies for the terrestrial water storage throughout the basin and subbasins. New hydrological insights for the region The main insight from this study is the agreement of the GLDAS anomalies with the SMAP data throughout the drought. The variable anomalies all decreased and showed alignment with the downscaled 1 km SMAP which shows alignment with the trends from in-situ observations. It was also found that the Upper Parana subbasin lost the most water over the drought period. These products improve understanding of the spatial variability within the entire basin and facilitate understanding of droughts and resources to assist in the future management of water resources.

La Plata Basin↗
DOE OSTI2024

Transforming an Ionic Conductor into an Electronic Conductor via Crystallization: In Situ Evolution of Transference Numbers and Structure in (La,Sr)(Ga,Fe)O 3–x Perovskite Thin Films

Mixed-conducting perovskites are workhorse electrochemically active materials, but typical high-temperature processing compromises their catalytic activity and chemo-mechanical integrity. Low-temperature pulsed laser deposition of amorphous films plus mild thermal annealing is an emerging route to form homogeneous mixed conductors with exceptional catalytic activity, but little is known about the evolution of the oxide-ion transport and transference numbers during crystallization. Here the coupled evolution of ionic and electronic transport behavior and structure in room-temperature-grown amorphous (La,Sr)(Ga,Fe)O 3-x films as they crystallize is explored. In situ ac-impedance spectroscopy with and without blocking electrodes, simultaneous capturing-synchrotron-grazing-incidence X-ray diffraction, dc polarization, transmission electron microscopy, and molecular dynamics simulations to evaluate isothermal and non-isothermal crystallization effects and the role of grain boundaries on transference numbers is combined. Ionic conductivity increases by ≈2 orders of magnitude during crystallization, with even larger increases in electronic conductivity. Consequently, as crystallinity increases, LSGF transitions from a predominantly ionic conductor to a predominantly electronic conductor. The roles of evolving lattice structural order, microstructure, and defect chemistry are examined. Grain boundaries appear relatively nonblocking electronically but significantly blocking ionically. The results demonstrate that ionic transference numbers can be tailored over a wide range by tuning crystallinity and microstructure without having to change the cation composition.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nickelate Superconductivity without Rare‐Earth Magnetism: (La,Sr)NiO 2

Abstract The occurrence of unconventional superconductivity in cuprates has long motivated the search for manifestations in other layered transition metal oxides. Recently, superconductivity is found in infinite‐layer nickelate (Nd,Sr)NiO 2 and (Pr,Sr)NiO 2 thin films, formed by topotactic reduction from the perovskite precursor phase. A topic of much current interest is whether rare‐earth moments are essential for superconductivity in this system. In this study, it is found that with significant materials optimization, substantial portions of the La 1− x Sr x NiO 2 phase diagram can enter the regime of coherent low‐temperature transport ( x = 0.14 ‐ 0.20), with subsequent superconducting transitions and a maximum onset of ≈9 K at x = 0.20. Additionally, the unexpected indication of a superconducting ground state in undoped LaNiO 2 is observed, which likely reflects the self‐doped nature of the electronic structure. Combining the results of (La/Pr/Nd) 1− x Sr x NiO 2 reveals a generalized superconducting dome, characterized by systematic shifts in the unit cell volume and in the relative electron‐hole populations across the lanthanides.

Osada, Motoki↗
DOE OSTI2024

Performance Prediction of High‐Entropy Perovskites La 0.8 Sr 0.2 Mn x Co y Fe z O 3 with Automated High‐Throughput Characterization of Combinatorial Libraries and Machine Learning

Perovskite oxides form a large family of materials with applications across various fields, owing to their structural and chemical flexibility. Efficient exploration of this extensive compositional space is now achievable through automated high-throughput experimentation combined with machine learning. In this study, we investigate the composition–structure–performance relationships of high-entropy La 0.8 Sr 0.2 Mn x Co y Fe z O 3±𝞭 perovskite oxides (0 < x, y, z <1; x+y+z≈1) for application as oxygen electrodes in Solid Oxide Cells. Following the deposition of a continuous compositional map using thin-film combinatorial pulsed laser deposition, compositional, structural, and performance properties are characterized using six different techniques with mapping capabilities. Random forests effectively model electrochemical performance, consistently identifying Fe-rich oxides as optimal compounds with the lowest area-specific resistance values for oxygen electrodes at 700 °C. Additionally, the models identify a statistical correlation between oxygen sublattice distortion—derived from spectral analysis of Raman-active modes—and enhanced performance.

high entropy oxides↗
DOE OSTI2025

Structural Phase Separation and Enhanced Superconductivity in La 1.875 Ba 0.125 CuO 4 Under Uniaxial Strain

Strain engineering has attracted significant attention in recent years due to its capability in tuning lattice and electronic structures of quantum materials. Using moderate uniaxial compressive strain, structural phase separation is induced in the low-temperature phase of x = 1/8 La 2-x Ba x CuO 4 (LBCO) single crystals. These structures are low temperature tetragonal (LTT), low temperature less orthorhombic (LTLO), and a plastically deformed nano-domain structure (PDNS), comprised of few-nanometer-sized orthorhombic domains within an amorphous matrix. These three structures exhibit distinct superconducting behaviors. The volume fraction of the LTT structure is suppressed with increasing strain, while its superconducting transition temperature increases and broadens. The LTLO structure exhibits a sharp superconducting transition above 32 K, which increases up to ≈ 36 K at maximum strain. The PDNS phase exhibits a very broad superconducting transition and persists even after removing the strain. This study illustrates the sensitivity of superconductivity to the structure of the LBCO sample near its stripe instability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Beneficial Effects of La 0.5 Sr 0.5 CoO 3 Coatings on Thin‐Film LiMn 2 O 4 Cathodes for Lithium Ion Batteries

Abstract The severe capacity loss of spinel LiMn 2 O 4 (LMO) limits the utility of this otherwise promising lithium ion battery cathode material. One of the strategies to mitigate capacity fade is applying a coating on LMO particle surfaces. While this approach yields promising results, there is limited understanding of mechanisms whereby coatings improve LMO capacity retention. Herein, the effects of a new protective coating material, La 0.5 Sr 0.5 CoO 3 (LSCO), in a thin‐film battery geometry that is amenable to fundamental studies of electrode processes, are reported. RF sputtering deposition is used to produce high quality 25–100 nm LMO cathodes on Al 2 O 3 substrates with an intervening Pt/Ti back‐side contact layer. Cycling of the un‐coated cathodes results in capacity loss of 18% over 300 cycles. Adding a 2 nm LSCO layer reduces the capacity loss to 3%. While this may be due in part to reduced Mn dissolution, scanning transmission electron microscopy results indicate that the coating helps to preserve crystallinity and reduce lattice structure distortion due to inhibited formation of defect tetragonal spinel. Three‐electrode electrochemical impedance spectroscopy results reveal that the LSCO coating increases charge transfer and ohmic resistances, but the increases are generally too small to significantly impact cell performance even at high C‐rates.

25 ENERGY STORAGE↗