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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Dy(CrSi)2 by Materials Project

DyCr2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 2.99 Å. Cr+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing CrSi4 tetrahedra. All Cr–Si bond lengths are 2.40 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Cr+2.50+, and one Si4- atom. The Si–Si bond length is 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(CuSi)2 by Materials Project

DyCu2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.05 Å. Cu+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing CuSi4 tetrahedra. All Cu–Si bond lengths are 2.38 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Cu+2.50+, and one Si4- atom. The Si–Si bond length is 2.35 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(SiRu)2 by Materials Project

DyRu2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a 8-coordinate geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.22 Å. Ru+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing RuSi4 tetrahedra. All Ru–Si bond lengths are 2.38 Å. Si4- is bonded in a 4-coordinate geometry to four equivalent Dy3+ and four equivalent Ru+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(SiNi)2 by Materials Project

DyNi2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.05 Å. Ni+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing NiSi4 tetrahedra. All Ni–Si bond lengths are 2.30 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Ni+2.50+, and one Si4- atom. The Si–Si bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(FeSi)2 by Materials Project

DyFe2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.08 Å. Fe+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing FeSi4 tetrahedra. All Fe–Si bond lengths are 2.27 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Fe+2.50+, and one Si4- atom. The Si–Si bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(MnSi)2 by Materials Project

DyMn2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.02 Å. Mn+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing MnSi4 tetrahedra. All Mn–Si bond lengths are 2.36 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Mn+2.50+, and one Si4- atom. The Si–Si bond length is 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(CoB)2 by Materials Project

DyCo2B2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a body-centered cubic geometry to eight equivalent B3- atoms. All Dy–B bond lengths are 2.88 Å. Co+1.50+ is bonded to four equivalent B3- atoms to form a mixture of distorted edge and corner-sharing CoB4 tetrahedra. All Co–B bond lengths are 2.00 Å. B3- is bonded in a 4-coordinate geometry to four equivalent Dy3+ and four equivalent Co+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(NiP)2 by Materials Project

DyNi2P2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a distorted body-centered cubic geometry to eight equivalent P3- atoms. All Dy–P bond lengths are 2.97 Å. Ni+1.50+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. All Ni–P bond lengths are 2.27 Å. P3- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Ni+1.50+, and one P3- atom. The P–P bond length is 2.31 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(CoSi)2 by Materials Project

DyCo2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Dy–Si bond lengths are 3.01 Å. Co+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing CoSi4 tetrahedra. All Co–Si bond lengths are 2.27 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Co+2.50+, and one Si4- atom. The Si–Si bond length is 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(Mo3S4)2 by Materials Project

DyMo6S8 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Dy3+ is bonded in a body-centered cubic geometry to eight S2- atoms. There are two shorter (2.71 Å) and six longer (3.00 Å) Dy–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 2.42–2.59 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to one Dy3+ and three equivalent Mo+2.17+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to one Dy3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(SiAg)2 by Materials Project

DyAg2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Dy3+ is bonded to eight equivalent Si4- atoms to form DySi8 hexagonal bipyramids that share corners with sixteen equivalent AgSi4 tetrahedra, edges with four equivalent DySi8 hexagonal bipyramids, edges with eight equivalent AgSi4 tetrahedra, and faces with four equivalent DySi8 hexagonal bipyramids. All Dy–Si bond lengths are 3.15 Å. Ag+2.50+ is bonded to four equivalent Si4- atoms to form AgSi4 tetrahedra that share corners with eight equivalent DySi8 hexagonal bipyramids, corners with four equivalent AgSi4 tetrahedra, edges with four equivalent DySi8 hexagonal bipyramids, and edges with four equivalent AgSi4 tetrahedra. All Ag–Si bond lengths are 2.60 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Dy3+, four equivalent Ag+2.50+, and one Si4- atom. The Si–Si bond length is 2.29 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(InPt)4 by Materials Project

DyPt4In4 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Dy3+ is bonded in a 8-coordinate geometry to eight Pt2- atoms. There are six shorter (3.01 Å) and two longer (3.14 Å) Dy–Pt bond lengths. There are two inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded in a distorted body-centered cubic geometry to one Dy3+ and seven In+1.25+ atoms. There are a spread of Pt–In bond distances ranging from 2.76–2.88 Å. In the second Pt2- site, Pt2- is bonded in a 8-coordinate geometry to three equivalent Dy3+ and four In+1.25+ atoms. There are three shorter (2.78 Å) and one longer (2.82 Å) Pt–In bond lengths. There are two inequivalent In+1.25+ sites. In the first In+1.25+ site, In+1.25+ is bonded in a distorted pentagonal planar geometry to five Pt2- atoms. In the second In+1.25+ site, In+1.25+ is bonded in a distorted hexagonal planar geometry to six Pt2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Microstructure refinement of hot deformed Dy-free NdFeB magnets through a novel cold sintering approach by pressure-assisted spark plasma sintering

Anisotropic fine-grained Dy-free NdFeB high-performance magnets were produced using a novel cold sintering approach by pressure-assisted spark plasma sintering (SPS). The NdFeB nanocrystalline ribbon powders were subjected to cold sintering below 450 °C using pressure-assisted SPS, followed by hot deformation at 710 °C and 810 °C via SPS. Results indicate that cold sintering below 450 °C effectively restricts grain growth in the NdFeB magnets, yielding sub-100 nm scale grains across both fine-grained regions and most coarse-grained regions. The refined grain structure achieved through cold sintering allows for a lower hot deformation temperature as compared with the magnet by conventional sintering, as finer grains allow easier deformation and grain sliding/rotation. This process produces a highly fine-grained and anisotropic microstructure to achieve high magnetic performance (i.e., high intrinsic coercivity, remanence, and maximum energy product) in the magnets. The cold sintering (at 350 °C) and lower hot deformation temperatures required (e.g., 710 °C) help control grain coarsening and limit grain size that is commensurate with the size of a single magnetic domain of the Nd 2 Fe 14 B magnetic matrix phase, resulting in high intrinsic coercivity (H ci =11.4 kOe). Furthermore, the reduced hot deformation temperature mitigates the formation of coarse grain bands, leading to improved magnetic properties, specifically an increased remanence (B r = 14.3 kGs) and a high maximum energy product ((BH) max = 48 MGOe). In conclusion, cold sintered hot deformed NdFeB magnet also shows good thermal stability with reversible temperature coefficient α(B r )= -0.097 %/K and α(H ci )= -0.616 %/K at elevated temperatures up to 400 K.

Cold Sintering↗
DOE OSTI2024

Tailored (La 0.2 Pr 0.2 Nd 0.2 Tb 0.2 Dy 0.2 ) 2 Ce 2 O 7 as a Highly Active and Stable Nanocatalyst for the Oxygen Evolution Reaction

Abstract Designing highly active and robust catalysts for the oxygen evolution reaction is key to improving the overall efficiency of the water splitting reaction. It has been previously demonstrated that evaporation induced self‐assembly (EISA) can be used to synthesize highly porous and high surface area cerate‐based fluorite nanocatalysts, and that substitution of Ce with 50% rare earth (RE) cations significantly improves electrocatalyst activity. Herein, the defect structure of the best performing nanocatalyst in the series are further explored, Nd 2 Ce 2 O 7 , with a combination of neutron diffraction and neutron pair distribution function analysis. It is found that Nd 3 + cation substitution for Ce in the CeO 2 fluorite lattice introduces higher levels of oxygen Frenkel defects and induces a partially reduced RE 1.5 Ce 1.5 O 5 +x phase with oxygen vacancy ordering. Significantly, it is demonstrated that the concentration of oxygen Frenkel defects and improved electrocatalytic activity can be further enhanced by increasing the compositional complexity (number of RE cations involved) in the substitution. The resulting novel compositionally‐complex fluorite– (La 0.2 Pr 0.2 Nd 0.2 Tb 0.2 Dy 0.2 ) 2 Ce 2 O 7 is shown to display a low OER overpotential of 210 mV at a current density of 10 mAcm −2 in 1M KOH, and excellent cycling stability. It is suggested that increasing the compositional complexity of fluorite nanocatalysts expands the ability to tailor catalyst design.

Chemistry↗
DOE OSTI2025

Interstitial Atoms and the Frustrated and Allowed Structural Transitions Principle: Tunability in the Electronic Structure of AuCu 3 ‐type Frameworks in Dy 4 T 1− x Ga 12 (T = Ag, Ir)

In this Article, we explore how the chemical pressure (CP) features of an intermetallic phase may provide opportunities to couple perturbations in electron count with the stabilization of the underlying geometrical structure. AuCu 3 ‐type LnGa 3 (Ln = lanthanide or group 3 metal) phases contain octahedral cavities of negative CP held open by overly compressed Ln–Ga interactions, leading to a series of transition metal‐stuffed derivatives. We present new additions to this family with the synthesis and crystal structures of Dy 4 T 1−x Ga 12 with (T, x) = (Ag, 0.29) and (Ir, 0.15), adopting Y 4 PdGa 12 ‐type superstructures of the AuCu 3 ‐type. density functional Ttheory (DFT)‐CP calculations, when adjusted to avoid dipolar CP features, affirm that T atom incorporation provides a mechanism for the relief of packing tensions, while electronic density of states distributions illustrate that the T atoms serve largely as electron or hole donors to the band structure, as needed for them to attain d 10 configurations. The maximum obtainable value for x may be limited by a mismatch between the Fermi energy and pseudogap, in line with the balance of factors envisioned by the frustrated and allowed structural transitions principle. Furthermore, trends in resistivity measurements on T = Ir, Pd, and Ag compounds are interpretable in terms of the varying degrees of disorder arising from x < 1.0.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Temperature and anion ligand field dependence of LnCl 3 (Ln = Nd, Dy, Sm) electronic absorption spectra in LiCl–KCl eutectic molten salt

A comprehensive knowledge of the coordination, bonding, and speciation of elements in molten salt mixtures is necessary to understand and predict the chemical and physical properties of the salt. Absorption spectroscopy can yield information about the chemistry of species of interest in alkali halide molten salt mixtures by revealing information about the electronic structure and transitions of those species. In this study, ultraviolet (UV), visible (vis), and near-infrared (NIR) absorption spectroscopy was used to examine changes to the electronic structure of trivalent Nd, Sm, and Dy in LiCl–KCl eutectic molten salt with changes in temperature and the anion composition of the melt. With increasing temperature, changes to spectral features suggest a distortion of the coordination complexes. Changes to lineshape with the substitution of alternative halide anions were examined and analyzed, revealing differences in the coordination for I – versus F – with the lanthanides. Gaussian peak fitting was used to show that the changes in lineshape with the progressive addition of F – anions can be explained by the superposition of a set of absorption bands from complexes with all Cl – anion ligands and a set of blueshifted absorption bands from complexes containing both F – and Cl – anion ligands. Finally, this work yields a new method to analyze and interpret change to electronic absorption spectra for f-block elements dissolved in alkali halide molten salts as well as new observations of the interactions of larger and smaller halide anions with lanthanides in Cl – -based molten salts.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Crystal Growth and Elemental Homogeneity of the Multicomponent Rare-Earth Garnet (Lu 1/6 Y 1/6 Ho 1/6 Dy 1/6 Tb 1/6 Gd 1/6 ) 3 Al 5 O 12

We report high-entropy aluminum garnets were grown as bulk single crystals using the micro-pulling-down method, taking the synthesis of complex ceramics a step further from the conventional preparation of polycrystalline materials. We studied the effects of growth parameters on the elemental distribution in high optical quality crystals of (Lu 1/6 Y 1/6 Ho 1/6 Dy 1/6 Tb 1/6 Gd 1/6 ) 3 Al 5 O 12 containing six cations (yttrium and rare-earths) taken in equimolar amounts. A single garnet structure was confirmed by powder X-ray diffraction. Electron microprobe measurements were obtained to correlate the radial distribution of rare-earth elements with pulling rates and molten zone height. The nature of the elemental distribution in the radial direction was associated with ionic radius: smaller rare-earths concentrated in the center of the crystal, while larger rare-earths segregated toward the outer edge of the cylindrical crystal. Faster pulling rates led to a flattening of the concentration profiles toward the nominal concentration, promoting a more homogeneous radial elemental distribution, while varying the molten zone height did not have a significant effect. The demonstrated success with crystal growth enables the practical availability of single crystals of multicomponent aluminum garnets for further discovery of new phenomena and applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tunable Magnetic Exchange between Rare-Earth Metal 5d and Iron 3d States: A Case Study of the Multiple Magnetic Transitions in Gd 6 FeBi 2 and the Solid Solutions Dy 6– x Gd x FeBi 2 (1 ≤ x ≤ 5) with Curie Temperatures in the Range 120–350 K

In this paper, the room-temperature magnet Gd 6 FeBi 2 was comprehensively characterized by means of temperature-dependent single-crystal X-ray diffraction, magnetization measurements, and experimental electron density and electronic structure computations. This work explores the electron-spin effects of Fe on this structure and suggests that Gd6FeBi2 shows structural features and exchange interactions, which are clearly distinguishable from other analogues, including the solid solutions Dy 6–x Gd x FeBi 2 (0 ≤ x ≤ 5). The unique traits of Gd 6 FeBi 2 and its derivatives encompass abnormal variations of lattice parameters with the temperature, as well as the presence of multiple magnetic transitions of complex nature. Based on the comprehensive analyses, it can be suggested that the unique magnetic response in this material is the result from tunable Fe spin states, which are coupled with strong Gd 5d–Fe 3d interactions, which differ from other members of this large, structural family. In the ground state, according to density functional theory calculations, the Fe atom carries two net electrons, whose spins are coupled in an antiparallel fashion to the spins of the Gd electrons. Near the Curie temperature, the Fe net moment is reduced intermittently, coupled with a multiple of magnetic transitions. The magnetic correlations are manifested in unexpected variations of the lattice parameters as a function of temperature, suggesting spin–lattice interactions. Furthermore, this study emphasizes the important role of Gd 5d electrons in tuning Fe 3d-based magnetic contribution, which enables better understanding on the spin coupling in other related compounds and sheds light on the development of new magnetic and spintronic compounds.

36 MATERIALS SCIENCE↗