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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Eu(Ag2Sb)2 by Materials Project

EuAg4Sb2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Eu2+ is bonded to six equivalent Sb3- atoms to form edge-sharing EuSb6 octahedra. All Eu–Sb bond lengths are 3.31 Å. There are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 1-coordinate geometry to six Ag1+ and four equivalent Sb3- atoms. There are three shorter (2.95 Å) and three longer (3.02 Å) Ag–Ag bond lengths. There are one shorter (2.88 Å) and three longer (3.23 Å) Ag–Sb bond lengths. In the second Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to three equivalent Ag1+ and three equivalent Sb3- atoms. All Ag–Sb bond lengths are 2.84 Å. Sb3- is bonded in a 10-coordinate geometry to three equivalent Eu2+ and seven Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(AsPt)2 by Materials Project

EuPt2As2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Eu2+ is bonded in a 8-coordinate geometry to eight Pt2- atoms. There are four shorter (3.38 Å) and four longer (3.43 Å) Eu–Pt bond lengths. There are two inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded in a 8-coordinate geometry to four equivalent Eu2+ and four equivalent As1+ atoms. All Pt–As bond lengths are 2.61 Å. In the second Pt2- site, Pt2- is bonded in a 5-coordinate geometry to four equivalent Eu2+ and five As1+ atoms. There are one shorter (2.49 Å) and four longer (2.55 Å) Pt–As bond lengths. There are two inequivalent As1+ sites. In the first As1+ site, As1+ is bonded to four equivalent Pt2- atoms to form a mixture of edge and corner-sharing AsPt4 tetrahedra. In the second As1+ site, As1+ is bonded in a 5-coordinate geometry to five Pt2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(Mo3Se4)2 by Materials Project

EuMo6Se8 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Eu2+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.94 Å) and six longer (3.19 Å) Eu–Se bond lengths. Mo+2.33+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.53–2.79 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Eu2+ and three equivalent Mo+2.33+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Eu2+ and four equivalent Mo+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ErSe2)2 by Materials Project

EuEr2Se4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–64°. There are a spread of Er–Se bond distances ranging from 2.79–2.87 Å. In the second Er3+ site, Er3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–64°. There are a spread of Er–Se bond distances ranging from 2.81–2.88 Å. Eu2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Eu–Se bond distances ranging from 3.18–3.42 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to three Er3+ and two equivalent Eu2+ atoms. In the second Se2- site, Se2- is bonded to three equivalent Er3+ and two equivalent Eu2+ atoms to form distorted edge-sharing SeEu2Er3 square pyramids. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to three Er3+ and two equivalent Eu2+ atoms. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to three equivalent Er3+ and two equivalent Eu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(P3Ru)4 by Materials Project

EuRu4P12 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Eu2+ is bonded to twelve equivalent P1- atoms to form EuP12 cuboctahedra that share faces with eight equivalent RuP6 octahedra. All Eu–P bond lengths are 3.13 Å. Ru+2.50+ is bonded to six equivalent P1- atoms to form RuP6 octahedra that share corners with six equivalent RuP6 octahedra and faces with two equivalent EuP12 cuboctahedra. The corner-sharing octahedral tilt angles are 63°. All Ru–P bond lengths are 2.37 Å. P1- is bonded in a 5-coordinate geometry to one Eu2+, two equivalent Ru+2.50+, and two equivalent P1- atoms. There are one shorter (2.29 Å) and one longer (2.32 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(AlS2)2 by Materials Project

EuAl2S4 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Eu2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (3.10 Å) and four longer (3.14 Å) Eu–S bond lengths. Al3+ is bonded to four S2- atoms to form edge-sharing AlS4 tetrahedra. There are a spread of Al–S bond distances ranging from 2.26–2.30 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent Eu2+ and two equivalent Al3+ atoms. In the second S2- site, S2- is bonded to two equivalent Eu2+ and two equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing SEu2Al2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GaSe2)2 by Materials Project

EuGa2Se4 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Eu2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are four shorter (3.26 Å) and four longer (3.29 Å) Eu–Se bond lengths. Ga3+ is bonded to four Se2- atoms to form edge-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.45–2.48 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Eu2+ and two equivalent Ga3+ atoms. In the second Se2- site, Se2- is bonded to two equivalent Eu2+ and two equivalent Ga3+ atoms to form a mixture of distorted edge and corner-sharing SeEu2Ga2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ZnSb)2 by Materials Project

EuZn2Sb2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Eu2+ is bonded to six equivalent Sb3- atoms to form EuSb6 octahedra that share corners with twelve equivalent ZnSb4 tetrahedra, edges with six equivalent EuSb6 octahedra, and edges with six equivalent ZnSb4 tetrahedra. All Eu–Sb bond lengths are 3.29 Å. Zn2+ is bonded to four equivalent Sb3- atoms to form ZnSb4 tetrahedra that share corners with six equivalent EuSb6 octahedra, corners with six equivalent ZnSb4 tetrahedra, edges with three equivalent EuSb6 octahedra, and edges with three equivalent ZnSb4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–54°. There are three shorter (2.74 Å) and one longer (2.81 Å) Zn–Sb bond lengths. Sb3- is bonded to three equivalent Eu2+ and four equivalent Zn2+ atoms to form a mixture of distorted edge and corner-sharing SbEu3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Aqueous phosphate detection using Eu(acac) 3

Currently, the majority of phosphate-sensitive phosphors reported in literature are metal-based complexes that require complicated and expensive synthesis to prepare. Here, in this study, we investigate the phosphate detecting capabilities of an inexpensive off-the-shelf phosphor: Eu(acac) 3 . We characterize its phosphate sensitivity as a function of sensor concentration and find that the quenching coefficient is inversely proportional to sensor concentration. This results in the limit-of-detection scaling linearly with sensor concentration. We determine its concentration-independent sensitivity to be 1.558 ± 0.012, which results in our lowest sensor concentration (44 μM) having a limit-of-detection of 3.39 ± 0.68 μM. We also find that for phosphate concentrations less than the sensor concentration, the fluorescence intensity ratio behaves linearly, but transitions to a non-linear functionality as the phosphate concentration exceeds the sensor concentration.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Energy System Transitions and Low-Emission Pathways in Australia, Brazil, Canada, China, EU-28, India, Indonesia, Japan, Republic of Korea, Russia, and United States

The Paris Agreement invited Parties to submit long-term, low-emission development strategies. This study presents national low-emission scenarios to inform such strategies for Australia, Brazil, Canada, China, EU, India, Indonesia, Japan, Russia, Republic of Korea and the USA. The study uses country-level energy–economy and integrated assessment models (IAMs) that incorporate detailed and disaggregated representations of the energy demand and supply systems that are difficult to capture in global IAMs. Models were used to explore low-carbon pathways up to 2050, providing insights in their implications for country emissions, energy system restructuring, energy–economy indicators and system costs. The analysis shows that the low-carbon scenarios of most economies studied here are consistent with pathways limiting global warming to below 2 °C.

Fragkos, Panagiotis↗
DOE OSTI2020

Computational modeling and neutron imaging to understand interface shape and solute segregation during the vertical gradient freeze growth of BaBrCl:Eu

In this work we apply continuum models to analyze phase change, heat transfer, fluid flow, solute transport, and segregation in order to understand prior neutron imaging observations of the vertical gradient freeze growth of Eu-doped BaBrCl. The models provide a rigorous framework in which to understand the mechanisms that are responsible for the complicated evolution of interface shape and dopant distribution in the growth experiment. We explain how a transition in the solid/liquid interface shape from concave to convex is driven by changes in radial heat transfer caused by furnace design. We also provide a mechanistic explanation of how dynamic growth conditions and changes of the flow structure in the melt result in complicated segregation patterns in this system. A growth pause caused by controller lock-up is shown to result in a band of solute depletion in accordance with classical theory. However, changing flow patterns during growth result in a non-monotonic axial distribution of solute that cannot be explained by simple application of classical segregation models. We assert that the approach presented here, namely the use of rigorous models in conjunction advanced diagnostics, such as neutron imaging, provides an exciting path forward for process optimization and control, accelerating the incremental advances that have, in the past, typically relied on empiricism, experience, and intuition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Analysis of chemical stress and the propensity for cracking during the vertical Bridgman growth of BaBrCl:Eu

Computational models are employed to analyze residual chemical stresses arising from compositional variations in europium-doped BaBrCl crystals grown by the vertical Bridgman method. We find that significant chemical stress is produced by radial segregation of Eu in this system. In particular, the distribution of normal stresses is set by the radial concentration gradient, whose changing sign produces surface states in tension or compression. Additionally, crack opening from surface flaws will be promoted or suppressed by tensile or compressive surface stresses, respectively. Thus, crystal growth processing strategies that change the radial dopant concentration gradients are posited to affect the propensity for cracking. For this system, surface stresses are changed from states of tension to compression when the growth rate is increased, thus improving the chances to avoid cracking—a strategy that defies classical wisdom that dictates slower growth to improve outcomes. Similar strategies affecting segregation may prove beneficial to tailor chemical stress fields to reduce cracking in other crystal growth systems.

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

Gamma-ray spectroscopic characterization of long, rapidly-grown KSr 2 I 5 :Eu crystals

Collimation and volumetric studies were done to evaluate the gamma-ray spectroscopic performance of KSr 2 I 5 :Eu scintillators grown via the vertical Bridgman method. To demonstrate practical crystal growth for large-scale production, Ø1 in. × 6 in. long crystals were grown using fast pulling rates up to 5 mm/h and short cooling times. The long crystals were sectioned into shorter Ø1 in. cylinders to investigate sample-to-sample variation of scintillation properties, the effects of self-absorption and scintillation non-uniformity using different gamma-ray excitation configurations. The best light output and energy resolution achieved for the largest volume and aspect ratio crystals (60 cm 3 Ø1 in x 4.7 in. long) were 53,500 ph/MeV and 4.6% at 662 keV. Finally, we produced eight Ø1 in. × 1 in. (12.5 cm 3 ) cylindrical samples, four from each boule, with energy resolutions between 3.1%-3.5% at 662 keV.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Luminescence of alkali rare earth borates A 3 Ln(BO 3 ) 2 (A = Na, K; Ln = Eu, Tb)

Single crystals of a series of rare earth borates, A 3 Ln (BO 3 ) (A = Na, K; Ln = Eu, Tb), were synthesized using a boric acid/hydroxide melt. The Na 3 Ln (BO 3 ) 2 borates crystallized in the monoclinic system with space group P2 1 /n, and the K 3 Ln (BO 3 ) 2 borates crystallized in the orthorhombic system with space group Pnma. Here, the luminescence of these borates was investigated under ultraviolet and X-ray excitations for the first time. Radioluminescence (RL) measurements showed K 3 Tb(BO 3 ) 2 to be the brightest compound, with an integral intensity equal to 55% of the integral emission of Bi 4 Ge 3 O 12 (BGO) powder.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evolution of Highly Anisotropic Magnetism in the Titanium-Based Kagome Metals LnTi 3 Bi 4 (Ln: La···Gd 3+ , Eu 2+ , Yb 2+ )

Here, we present a family of titanium-based kagome metals of the form LnTi 3 Bi 4 (Ln: La···Gd 3+ , Eu 2+ , Yb 2+ ). Four previously unreported compounds are presented: YbTi 3 Bi 4 , GdTi 3 Bi 4 , NdTi 3 Bi 4 , and PrTi 3 Bi 4 . Single-crystal growth methods are provided alongside detailed magnetic and thermodynamic measurements across the entire series. The LnTi 3 Bi 4 family of compounds are orthorhombic (Fmmm), layered compounds that exhibit slightly distorted titanium-based kagome nets interwoven with zigzag lanthanide-based (Ln) chains. Crystals are easily exfoliated parallel to the kagome sheets, and angular resolved photoemission (ARPES) measurements highlight the intricacy of the electronic structure in these compounds. Density functional theory (DFT) and ARPES studies find Dirac points near the Fermi level, consistent with the kagome-derived band structure. The magnetic properties and the associated anisotropy emerge from the quasi-1D zigzag chains of Ln and impart a wide array of magnetic ground states ranging from anisotropic ferromagnetism to complex antiferromagnetism with a cascade of metamagnetic transitions. In conclusion, the combination of the kagome-based electronic structure and highly anisotropic Ln-based magnetism on an exfoliatable platform cements the LnTi 3 Bi 4 family as an interesting addition to the ever-expanding suite of kagome metals.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Advanced Analysis of X-ray Fluorescence Measurements of the Interfacial Density of Eu Ions at Liquid–Liquid Interfaces for Solvent Back-Extraction

X-ray fluorescence near total reflection (XFNTR) is the primary technique used to measure the element-specific interfacial density of ions at liquid−liquid interfaces. Fluorescence from ions in the bulk liquids can complicate the determination of the interfacial density; consequently, measurements have been previously limited to samples without ions in the upper phase and with concentrations on the order of 10 μM or less in the lower phase. We modify the analysis of XFNTR data to account for ions in both bulk phases, then demonstrate its use in the context of rare-earth separations processes. In a model of ion stripping (i.e., back-extraction), dodecane solutions of di(2-ethylhexyl)- phosphoric acid (HDEHP) loaded with Eu(III) at the 1 mM level are placed in contact with either pure water or aqueous solutions of nitric or citric acid at pH 3. XFNTR measurements of equilibrated, quiescent samples reveal that citric acid solutions produce a disproportionately large depletion of ions from the interface compared to that from the bulk organic solution, whereas stripping by pure water or nitric acid solutions is negligible. As a result, this advance in the methodology of XFNTR may have broad applicability to the investigation of metal ions in chemical and biological processes at liquid−liquid interfaces.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗