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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ce(BRh)4 by Materials Project

Ce(RhB)4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are four shorter (2.99 Å) and eight longer (3.18 Å) Ce–Rh bond lengths. There are eight shorter (3.04 Å) and four longer (3.17 Å) Ce–B bond lengths. Rh is bonded in a 5-coordinate geometry to three equivalent Ce and five equivalent B atoms. There are a spread of Rh–B bond distances ranging from 2.22–2.27 Å. B is bonded in a 6-coordinate geometry to three equivalent Ce, five equivalent Rh, and one B atom. The B–B bond length is 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(Sn2Rh)2 by Materials Project

Ce(RhSn2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ce is bonded in a 6-coordinate geometry to seven Sn atoms. There are a spread of Ce–Sn bond distances ranging from 3.18–3.37 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 7-coordinate geometry to seven Sn atoms. There are a spread of Rh–Sn bond distances ranging from 2.71–2.89 Å. In the second Rh site, Rh is bonded in a 7-coordinate geometry to seven Sn atoms. There are a spread of Rh–Sn bond distances ranging from 2.70–2.83 Å. There are four inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to two equivalent Ce and four Rh atoms. In the second Sn site, Sn is bonded in a 5-coordinate geometry to two equivalent Ce and three equivalent Rh atoms. In the third Sn site, Sn is bonded in a 3-coordinate geometry to three equivalent Ce and three equivalent Rh atoms. In the fourth Sn site, Sn is bonded to four Rh atoms to form a mixture of distorted edge and corner-sharing SnRh4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(Ge2Rh3)2 by Materials Project

Ce(Rh3Ge2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ce is bonded to six equivalent Rh and six equivalent Ge atoms to form face-sharing CeGe6Rh6 cuboctahedra. All Ce–Rh bond lengths are 3.16 Å. All Ce–Ge bond lengths are 3.15 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.50 Å) and four longer (2.57 Å) Rh–Ge bond lengths. In the second Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Ce and four Ge atoms. There are two shorter (2.49 Å) and two longer (2.57 Å) Rh–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to nine Rh atoms. In the second Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Ce and six Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(SiIr)2 by Materials Project

CeIr2Si2 crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Ce is bonded in a 8-coordinate geometry to eight Ir and eight equivalent Si atoms. There are four shorter (3.24 Å) and four longer (3.26 Å) Ce–Ir bond lengths. There are four shorter (3.27 Å) and four longer (3.31 Å) Ce–Si bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Ce, one Ir, and four equivalent Si atoms. The Ir–Ir bond length is 2.65 Å. All Ir–Si bond lengths are 2.42 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Ce, one Ir, and four equivalent Si atoms. All Ir–Si bond lengths are 2.42 Å. Si is bonded in a 4-coordinate geometry to four equivalent Ce and four Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Characterization of EJ-270 and Ce-doped LiCAF scintillators for the development of high-rate neutron reflectometer detectors

The Second Target Station of the Spallation Neutron Source at Oak Ridge National Laboratory is anticipated to provide a neutron source with ∼20 times increase in peak brightness than the First Target Station. The neutron reflectometers currently in operation at the First Target Station need to be upgraded due to the increased neutron flux. A prototype neutron detector module based upon a pixelated scintillator array readout by silicon photomultipliers is being developed to address the high-rate challenge faced with future neutron reflectometer instruments at the Second Target Station. Two types of scintillator materials were considered for this detector development, i.e., 6 Li-loaded EJ-270 plastic scintillator and Ce-doped LiCAF single crystal. This paper reports the scintillator characterization results, including light yield, pulse shape discrimination performance, capability to detect thermal neutrons in a high γ-ray field, and γ-ray sensitivity. The number of photons produced per neutron capture by EJ-270 and LiCAF:Ce was measured to be 2176 ± 91 and 2651 ± 108, respectively. EJ-270 demonstrated a good capability to discriminate between neutrons and γ-rays by employing the commonly used charge comparison method (figure-of-merit: 1.13 ± 0.01 for an energy cut of 292–426 keVee) and a reasonable performance when using the time-over-threshold techniques; however, no discrimination was observed from LiCAF:Ce regardless of the pulse shape discrimination approaches utilized, making pulse height discrimination necessary for LiCAF:Ce to differentiate between neutrons and γ-rays. Both EJ-270 and LiCAF:Ce exhibited an acceptable capacity to detect thermal neutrons at high exposure rates up to approximately 584 mR/h. Furthermore, the γ-ray sensitivities measured with a 60 Co source at an exposure rate of around 1145 mR/h were determined to be (6.11 ± 0.87) × 10 −6 and (7.64 ± 1.08) × 10 −7 for EJ-270 and LiCAF:Ce, respectively.

EJ-270↗
DOE OSTI2025

Electronic and reactivity changes in epitaxially grown Ce 1-x Zr x O 2-δ (111) thin films

Ceria composite catalysts have long been used for ketonization reactions, which is a valuable chemistry for the upgrading of biomass-derived carboxylates. To better understand the interaction of zirconia with ceria in the context of ketonization, thin epitaxial films of ceria-zirconia mixed metal oxide Ce 1-x Zr x O 2-δ (x = 0-1) were grown on a Pt(111) substrate in ultrahigh vacuum conditions and studied with X-ray photoelectron spectroscopy (XPS). Core level and valence band XPS results suggest a strong interaction between ceria and zirconia cations, possibly due to increased filling of unoccupied 4f 0 orbitals of ceria from neighboring Zr cations in the lattice structure. This leads to a partial reduction of ceria from Ce 4+ to Ce 3+ , with Zr remaining predominantly in the 4+ oxidation state. Ketonization of acetic acid was studied using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). These results found ketonization over mixed Ce-Zr composite oxides exhibited lower activation energies than for pure CeO 2 and ZrO 2 , with Ce 0.38 Zr 0.62 O 2-δ exhibiting the highest yield of acetone among the studied surfaces. In conclusion, these results suggest the high activity of Ce-Zr catalysts appears to be a result of oxygen vacancy formation, stabilized by electron donation from Zr cations.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Transformation of CeO 2 Nanoparticles into Atomically Dispersed Ce Cations Leads to Enhanced Reactivity for Automotive Emissions Control

Nanosized cerium oxide (CeO 2 ) has been extensively used as the oxygen storage component in automotive emission control systems. However, the possible influence of atomically dispersed Ce in these catalysts has not been recognized. Here, in this study, we demonstrate the controllable transformation of ceria nanoparticles into isolated cerium cations on γ-Al 2 O 3 via reductive atom trapping in 10% H 2 at 800 °C, achieving over half-monolayer coverage. Dispersed Ce 1 ions anchored by surface penta- and octa-coordinated Al sites exhibit outstanding thermal stability in air up to 500 °C, enabling further loading of active metals with well-defined catalyst structures. With this strategy, supported single-atom Rh 1 surrounded by dispersed Ce 1 is confirmed to exhibit much superior performance to Rh 1 on bare Al 2 O 3 or nanocrystalline CeO 2 in catalyzing NO reduction by CO, exhibiting a striking one-order-of-magnitude increase in activity. Dispersed Ce 1 exhibits greatly enhanced oxygen transfer capability compared to ceria nanoparticles and introduces a modified reaction mechanism that involves an adjacent Rh 1 –Ce 1 motif, resulting in a greatly decreased activation barrier (from 192 to 96 kJ/mol). The reactivity enhancements are also seen with Ce 1 -promoted Pt nanoparticles for oxidation of CO and hydrocarbons.

Jiang, Dong [Washington State Univ., Pullman, WA (↗
DOE OSTI2025

Isolation of Ce( IV ) centered polyoxoalkoxide sandwich-type complexes allows comparison of metal–oxygen bond covalency

The new Ce III centered sandwich-type complex (TBA) 3 [Ce{W 4 O 13 (OMe) 4 MoNO} 2 ] is reported. The redox properties of this molecule, and its all-molybdenum analogue, (TBA) 3 [Ce{Mo 5 O 13 (OMe) 4 NO} 2 ], were investigated using cyclic voltammetry. The data reveals the presence of reversible Ce IV /Ce III redox couples at modest potentials. One electron oxidation of the complexes provides facile access to the corresponding Ce IV derivatives, which were fully characterized. 17 O NMR spectroscopy reveals that the chemical shifts of the oxygen nuclei directly bound to Ce IV are much higher than the corresponding signals in isostructural, diamagnetic, Zr IV , Hf IV , or Th IV centered complexes. Density functional theory (DFT) calculations indicate that the increase in chemical shift correlates with an increase in the covalency of the M IV –O bonds, illustrating that 17 O NMR spectroscopy is a powerful experimental tool for interrogating the nature of metal oxygen bonding in diamagnetic complexes.

Shiels, Dominic [Univ. of Rochester, NY (United St↗
DOE OSTI2023

Localized 𝑓-electron magnetism in the semimetal Ce 3 ⁢ Bi 4 ⁢ Au 3

Ce 3 ⁢Bi 4 ⁢ Au 3 crystallizes in the same noncentrosymmetric cubic structure as the prototypical Kondo insulator Ce 3 ⁢ Bi 4 ⁢Pt 3 . Here we report the physical properties of Ce 3 ⁢Bi 4 ⁢ Au 3 single crystals using magnetization, thermodynamic, and electrical-transport measurements. Magnetic-susceptibility and heat-capacity data reveal antiferromagnetic order below 𝑇 𝑁 =3.2K. The magnetic entropy 𝑆 mag reaches 𝑅⁢ ln⁡ 2 slightly above 𝑇 𝑁 , which suggests localized 4⁢𝑓 moments in a doublet ground state. Multiple field-induced magnetic transitions are observed at temperatures below 𝑇 𝑁 , which indicate a complex spin structure with competing interactions. Ce 3 ⁢Bi 4 ⁢ Au 3 shows semimetallic behavior in electrical resistivity in contrast to the majority of reported cerium-based 343 compounds which are semiconducting. Electrical-resistivity measurements under hydrostatic pressure reveal a slight enhancement of 𝑇 𝑁 under pressures up to 2.3 GPa, which supports a scenario wherein Ce 3 ⁢Bi 4 ⁢Au 3 belongs to the far left of the Doniach phase diagram dominated by Ruderman-Kittel-Kasuya-Yosida interactions. Using realistic many-body simulations, we confirm the semimetallic electronic structure of Ce 3 ⁢Bi 4 ⁢ Au 3 and quantitatively reproduce its local moment behavior in the paramagnetic state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

X-ray spectroscopic investigation of crystal fields in Ce 2 Rh 1 − x Ir x In 8 heavy fermions

The higher dimensionality in the crystal fields of the Ce 2 M In 8 ( M = Rh , Ir ) compounds and its interplay with hybridization and disorder are key ingredients to understand the complex phase diagrams by this family, which have been explored extensively by macroscopic techniques. Here, we present an investigation of the crystal-electric field schemes of Ce 2 Rh 1 − x Ir x In 8 using x-ray absorption spectroscopy. Our full multiplet calculations for the 4 f 1 configuration of Ce 3 + to describe the temperature-dependent linear dichroism in Ce 2 M In 8 are consistent with a Γ 7 1 = 1 − α 2 · | ∓ 3 2 〉 − | α | · | ± 5 2 〉 ground state containing a predominant | ± 3 / 2 〉 contribution that increases further with x . This enhancement is believed to favor superconductivity in Ce-based heavy fermion materials, observed in previous results in the Ce M In 5 family. Our recent observations shed light on the unexpected emergence of the ambient-pressure superconducting dome in the center of the composition phase diagram and its subsequent suppression on the Ir-rich side due to the early onset of fluctuations associated with the structurally more disordered state, inferred from previous neutron magnetic diffraction experiments. Published by the American Physical Society 2024

Christovam, D. S. (ORCID:0000000250698107)↗
DOE OSTI2020

Theoretical Correlation of Elemental Distribution of Nd and Pr in Ce-Fe-B Microstructure With Hard Magnetic Properties

Relatively resource-rich but property inferior-Ce-Fe-B magnet can be improved by partial replacement of Ce by Nd and/or Pr. In addition to the amount of Nd/Pr, their distribution profile in microstructure plays an important role. From our first principles density functional theory (DFT) calculation, the substitution energy of Ce by Pr/Nd is negative in Ce 2 Fe 14 B (2:14:1) while that for laves phase, CeFe 2 is positive, implying that Nd/Pr stabilize 2:14:1 and suppress the formation of the CeFe 2 phase. Further, micromagnetic simulation indicates that homogenized distribution of Nd/Pr improves squareness of demagnetization curve, while core (Ce-rich)-shell (Nd/Pr-rich) 2:14:1 grain structure enhances coercivity. Magnetic properties of Ce-Fe-B can be optimized by manipulating distribution profile of chemical element in microstructure based on their subtle difference in thermodynamic property, which is an effective pathway to design optimized chemical composition and processing route for high-performance magnet.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Magnetic properties of Lutetium and Yttrium doped Ce 2 Fe 14 B magnets

The increasing demand for Nd-Dy and Sm-Co based permanent magnets is exacerbating the current critical materials shortage, therefore improving and optimizing current candidate critical element free permanent magnets is necessary to develop future clean energy technologies. In this work, we aim to increase the thermal stability and magnetic performance of Ce 2 Fe 14 B based permanent magnets through the substitution of Ce ions with noncritical rare earth elements Lu and Y. The substitution of Lu (x=0; 0.05; 0.1; 0.15) for Ce ions in (LuxCe 2-x )Fe 14 B was unsuccessful, likely due to disparities in ionic size and valencies, and failed to exhibit improved thermal stability or magnetic performance. In contrast, Y substitution for Ce ions in (Y x Ce 2-x )Fe14B (x= 0.1; 0.2; 0.3; 0.4; 0.5) alloys was successful. Notably, these alloys demonstrated enhanced thermal stability, as evidenced by an increase in the Curie temperature, reaching a peak of 443 K at x= 0.5. Y substitution also helped to suppress the CeFe2 Laves phase. Without loss of the anisotropy field Y substitution increased the saturation magnetization, MS, peaking at MS = 125 emu/g for a Y concentration of x= 0:4, demonstrating (Y 0.4 Ce 1.6 )Fe 14 B as a potential critical element free permanent magnet with an energy product as high as 29 MGOe. This work is advantageous in developing low cost high performance permanent magnets with reduced or little to no critical rare earth elements.

Rai, Binod K.↗
DOE OSTI2024

Effect of Minor Ce Additions on Corrosion Behavior of Experimental Pipeline Steel

Minor additions of rare earth elements (REEs) have been shown to improve various steel properties. In particular, Cerium (Ce), as a relatively abundant and inexpensive element, has received attention as a potentially beneficial minor alloying addition for a variety of steel applications, including pipelines materials. The objective of this work is to investigate the effect of Ce on corrosion performance of experimental high-strength pipeline steel. Electrochemical corrosion experiments were carried out on steel without and with 0.006, 0.018, and 0.03 wt.% of Ce in 3.5 wt.% NaCl saturated with CO2 at 20 oC. For comparison purposes, X100 carbon steel specimens machined from an experimental pipe with a yield strength of 731 MPa were tested under the same conditions. The electrochemical techniques employed included: potentiodynamic polarization (PDP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS). In addition, post-corrosion surface characterization was performed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), while crystalline phases were determined by X-ray diffraction (XRD). The corrosion of base metal without Ce was lower (0.15 mm/y) compared to carbon steel X100 (0.9 mm/yr). The electrochemical results showed that adding Ce accelerates corrosion rates compared to base metal without Ce. No pitting corrosion of tested steel was detected.

Belarbi, Zineb↗
DOE OSTI2020

Materials Data on Ce(AgGe)2 by Materials Project

CeAg2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ce is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Ge atoms. All Ce–Ag bond lengths are 3.53 Å. All Ce–Ge bond lengths are 3.28 Å. Ag is bonded to four equivalent Ce, four equivalent Ag, and four equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing AgCe4Ag4Ge4 cuboctahedra. All Ag–Ag bond lengths are 3.04 Å. All Ag–Ge bond lengths are 2.67 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ce, four equivalent Ag, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(GePd)2 by Materials Project

CePd2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ce is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Ce–Pd bond lengths are 3.35 Å. All Ce–Ge bond lengths are 3.29 Å. Pd is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ge atoms. All Pd–Ge bond lengths are 2.54 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ce, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(BRu)2 by Materials Project

CeRu2B2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ce is bonded in a 10-coordinate geometry to four equivalent Ru and six equivalent B atoms. All Ce–Ru bond lengths are 3.00 Å. There are two shorter (2.84 Å) and four longer (3.05 Å) Ce–B bond lengths. Ru is bonded in a 4-coordinate geometry to two equivalent Ce and four equivalent B atoms. There are two shorter (2.08 Å) and two longer (2.15 Å) Ru–B bond lengths. B is bonded in a 7-coordinate geometry to three equivalent Ce and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(Al10Co)2 by Materials Project

Ce(CoAl10)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ce is bonded in a 4-coordinate geometry to sixteen Al atoms. There are four shorter (3.12 Å) and twelve longer (3.21 Å) Ce–Al bond lengths. Co is bonded to twelve Al atoms to form corner-sharing CoAl12 cuboctahedra. There are six shorter (2.55 Å) and six longer (2.76 Å) Co–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded in a distorted linear geometry to two equivalent Ce and twelve equivalent Al atoms. All Al–Al bond lengths are 3.09 Å. In the second Al site, Al is bonded in a distorted linear geometry to two equivalent Co and ten Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.82 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to one Ce, one Co, and ten Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(CuGe)2 by Materials Project

CeCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ce is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Ce–Cu bond lengths are 3.29 Å. All Ce–Ge bond lengths are 3.19 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ge atoms. All Cu–Ge bond lengths are 2.45 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ce, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.50 Å.

36 MATERIALS SCIENCE↗