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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Thin film combinatorial sputtering of Al-Ce alloys: Investigating the phase separation of as-deposited solid solutions and determining the coefficient of thermal expansion

Al x Ce 100–x thin films with a composition range of ~75.0 < x < 99.5 at% (36.5 < x < 97.5 wt%) were synthesized via combinatorial co-sputtering from an Al and an Al 50 Ce 50 target. The crystal structure, phase fraction, film morphology, electrical resistivity, and temperature-dependent coefficients of thermal expansion (CTE) are all correlated to the Al x Ce 100–x composition. The as-deposited films form a metastable solid-solution, and annealing leads to the formation of the thermodynamically stable two-phase system of Al and the α-Al 11 Ce 3 intermetallic. Temperature dependent x-ray diffraction (XRD) reveals that the two phases expand independently of one another, and the thin film Al temperature-dependent CTE is similar to bulk Al. The thin film Al 11 Ce 3 intermetallic phase has a nearly constant CTE of ~1.5 × 10 –5 /°C within the temperature range studied (25–550 °C). To confirm the thin film Al 11 Ce 3 results, bulk stoichiometric Al 11 Ce 3 and +/- 1 wt% Ce samples were prepared and the CTE of each was measured with the same conditions. A Rietveld analysis of the bulk data enabled an estimation of the CTE in each of the 3 orthorhombic lattice parameters, which displayed anisotropic behavior. The thin film and bulk CTE measurements were in very good agreement. Estimations of the temperature dependent CTE of the two-phase alloys are made via the Reuss and Voigt models. Finally, by demonstrating the efficacy of the approach, more complex multi-component rapid materials discovery of low CTE Al-alloys can be pursued via the combinatorial thin film synthesis and XRD measurement.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Search for Stable and Low-Energy Ce–Co–Cu Ternary Compounds Using Machine Learning

Cerium-based intermetallics have garnered significant research attention as potential new permanent magnets. In this study, we explore the compositional and structural landscape of Ce−Co−Cu ternary compounds using a machine learning (ML)- guided framework integrated with first-principles calculations. We employ a crystal graph convolutional neural network (CGCNN), which enables efficient screening for promising candidates, significantly accelerating the material discovery process. With this approach, we predict five stable compounds, Ce 3 Co 3 Cu, CeCoCu 2 , Ce 12 Co 7 Cu, Ce 11 Co 9 Cu, and Ce 10 Co 11 Cu 4 , with formation energies below the convex hull, along with hundreds of low-energy (possibly metastable) Ce−Co−Cu ternary compounds. Firstprinciples calculations reveal that several structures are both energetically and dynamically stable. Notably, two Co-rich low-energy compounds, Ce 4 Co 33 Cu and Ce 4 Co 31 Cu 3 , are predicted to have high magnetizations.

Chemical structure↗
DOE OSTI2023

Multiple and nonlocal cation redox in Ca–Ce–Ti–Mn oxide perovskites for solar thermochemical applications

Modeling-driven design of redox-active off-stoichiometric oxides for solar thermochemical H 2 production (STCH) seldom has resulted in empirical demonstration of competitive materials. Here, we report the theoretical prediction and experimental evidence that the perovskite Ca 2/3 Ce 1/3 Ti 1/3 Mn 2/3 O 3 is synthesizable with high phase purity, stable, and has desirable redox thermodynamics for STCH, with a predicted average neutral oxygen vacancy (VO) formation energy, E v = 3.30 eV. Flow reactor experiments suggest potentially comparable or greater H 2 production capacity than recent promising Sr–La–Mn–Al and Ba–Ce–Mn metal oxide perovskites. Utilizing quantum-based modeling of a solid solution on both A and B sub-lattices, we predict the impact of nearest-neighbor composition on E v and determine that A-site Ce 4+ reduction dominates the redox-activity of Ca 2/3 Ce 1/3 Ti 1/3 Mn 2/3 O 3 . X-ray absorption spectroscopy measurements provide evidence that supports these predictions and reversible Ce 4+ -to-Ce 3+ reduction. Our models predict that Ce 4+ reduces even when it is not nearest-neighbor to the V O , suggesting that refinement of Ce stoichiometry has the possibility of further enhancing performance.

08 HYDROGEN↗
DOE OSTI2022

Ground state of Ce 3 Bi 4 Pd 3 unraveled by hydrostatic pressure

Noncentrosymmetric Ce 3 Bi 4 Pd 3 has attracted a lot of attention as a candidate for strongly correlated topological material, yet its experimental ground state remains a matter of contention. Two conflicting scenarios have emerged from a comparison to the prototypical Kondo insulator Ce 3 Bi 4 Pd 3 : Either Ce 3 Bi 4 Pd 3 is a spin-orbit-driven topological semimetal or a Kondo insulator with smaller Kondo coupling than its Pt counterpart. Here, we determine the ground state of Ce 3 Bi 4 Pd 3 via electrical resistivity measurements under hydrostatic pressure, which is a clean symmetry-preserving tuning parameter that increases hybridization but virtually preserves spin-orbit coupling. Ce 3 Bi 4 Pd 3 becomes more insulating under pressures up to 2.3 GPa, which is a signature of Ce-based Kondo insulating materials in the considered pressure range. Its small zero-pressure gap increases quadratically with pressure, similar to the behavior observed in the series Ce 3 Bi 4 (Pt 1 - x Pd x ) 3 , which indicates that Pt substitution and applied pressure have a similar effect. Finally, our result not only demonstrates that Kondo coupling, rather than spin-orbit coupling, is the main tuning parameter in this class of materials, but it also establishes that Ce 3 Bi 4 Pd 3 has a narrow-gap Kondo insulating ground state.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(SiIr)2 by Materials Project

CeIr2Si2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 4-coordinate geometry to eight Ir and eight Si atoms. There are four shorter (3.16 Å) and four longer (3.29 Å) Ce–Ir bond lengths. There are four shorter (3.19 Å) and four longer (3.20 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 and five Si atoms. There are one shorter (2.41 Å) and four longer (2.43 Å) Ir–Si bond lengths. In the second Ir site, Ir is bonded to four equivalent Ce and four equivalent Si atoms to form a mixture of distorted edge and face-sharing IrCe4Si4 tetrahedra. All Ir–Si bond lengths are 2.45 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent Ce and five Ir atoms. In the second Si site, Si is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(Re2Si)2 by Materials Project

Ce(Re2Si)2 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Re and eight equivalent Si atoms. There are four shorter (3.31 Å) and four longer (3.43 Å) Ce–Re bond lengths. All Ce–Si bond lengths are 3.16 Å. There are two inequivalent Re sites. In the first Re site, Re is bonded in a 12-coordinate geometry to two equivalent Ce, eight Re, and two equivalent Si atoms. There are a spread of Re–Re bond distances ranging from 2.64–2.91 Å. Both Re–Si bond lengths are 2.50 Å. In the second Re site, Re is bonded to two equivalent Ce, eight Re, and two equivalent Si atoms to form a mixture of distorted face, edge, and corner-sharing ReCe2Re8Si2 cuboctahedra. Both Re–Re bond lengths are 2.59 Å. Both Re–Si bond lengths are 2.54 Å. Si is bonded in a 9-coordinate geometry to four equivalent Ce, four Re, and one Si atom. The Si–Si bond length is 2.44 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(GeIr)2 by Materials Project

CeIr2Ge2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Ir and eight Ge atoms. There are four shorter (3.24 Å) and four longer (3.38 Å) Ce–Ir bond lengths. There are four shorter (3.27 Å) and four longer (3.28 Å) Ce–Ge bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.52 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Ce and five Ge atoms. There are one shorter (2.45 Å) and four longer (2.50 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Ce and five Ir atoms. In the second Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(SnPt)2 by Materials Project

CePt2Sn2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Pt and eight Sn atoms. There are a spread of Ce–Pt bond distances ranging from 3.47–3.52 Å. There are a spread of Ce–Sn bond distances ranging from 3.46–3.59 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Sn atoms. All Pt–Sn bond lengths are 2.68 Å. In the second Pt site, Pt is bonded in a 9-coordinate geometry to four equivalent Ce and five Sn atoms. There are one shorter (2.59 Å) and four longer (2.69 Å) Pt–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ce and five Pt atoms. In the second Sn site, Sn is bonded to four equivalent Ce and four equivalent Pt atoms to form a mixture of distorted face and edge-sharing SnCe4Pt4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(NiSn)2 by Materials Project

CeNi2Sn2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Ni and eight Sn atoms. There are four shorter (3.27 Å) and four longer (3.42 Å) Ce–Ni bond lengths. There are four shorter (3.34 Å) and four longer (3.44 Å) Ce–Sn bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 8-coordinate geometry to four equivalent Ce and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.56 Å. In the second Ni site, Ni is bonded in a 9-coordinate geometry to four equivalent Ce and five Sn atoms. There are one shorter (2.49 Å) and four longer (2.56 Å) Ni–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 12-coordinate geometry to four equivalent Ce and four equivalent Ni atoms. In the second Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ce and five Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(PIr)2 by Materials Project

CeIr2P2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Ir and eight P atoms. There are four shorter (3.19 Å) and four longer (3.23 Å) Ce–Ir bond lengths. There are four shorter (3.12 Å) and four longer (3.15 Å) Ce–P bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded to four equivalent Ce and four equivalent P atoms to form a mixture of distorted edge and face-sharing IrCe4P4 cuboctahedra. All Ir–P bond lengths are 2.48 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Ce and five P atoms. There are four shorter (2.35 Å) and one longer (2.36 Å) Ir–P bond lengths. There are two inequivalent P sites. In the first P site, P is bonded in a 8-coordinate geometry to four equivalent Ce and four equivalent Ir atoms. In the second P site, P is bonded in a 9-coordinate geometry to four equivalent Ce and five Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(CuSn)2 by Materials Project

CeCu2Sn2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Cu and eight Sn atoms. There are four shorter (3.36 Å) and four longer (3.44 Å) Ce–Cu bond lengths. There are four shorter (3.37 Å) and four longer (3.56 Å) Ce–Sn bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to four equivalent Ce and four equivalent Sn atoms. All Cu–Sn bond lengths are 2.61 Å. In the second Cu site, Cu is bonded in a 9-coordinate geometry to four equivalent Ce and five Sn atoms. There are one shorter (2.52 Å) and four longer (2.65 Å) Cu–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Cu atoms. In the second Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ce and five Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(AlPd)2 by Materials Project

CePd2Al2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Pd and eight Al atoms. There are four shorter (3.28 Å) and four longer (3.38 Å) Ce–Pd bond lengths. There are four shorter (3.31 Å) and four longer (3.37 Å) Ce–Al bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Ce and five Al atoms. There are one shorter (2.51 Å) and four longer (2.56 Å) Pd–Al bond lengths. In the second Pd site, Pd is bonded to four equivalent Ce and four equivalent Al atoms to form distorted PdCe4Al4 tetrahedra that share corners with twelve equivalent AlCe4Pd4 tetrahedra, edges with two equivalent AlCe4Pd4 tetrahedra, edges with four equivalent PdCe4Al4 tetrahedra, and faces with four equivalent PdCe4Al4 tetrahedra. All Pd–Al bond lengths are 2.52 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 5-coordinate geometry to four equivalent Ce and five Pd atoms. In the second Al site, Al is bonded to four equivalent Ce and four equivalent Pd atoms to form distorted AlCe4Pd4 tetrahedra that share corners with twelve equivalent PdCe4Al4 tetrahedra, edges with two equivalent PdCe4Al4 tetrahedra, edges with four equivalent AlCe4Pd4 tetrahedra, and faces with four equivalent AlCe4Pd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Multi‐electron Oxidation of Ce(III) Complexes Facilitated by Redox‐Active Ligands

A family of cerium complexes featuring a redox-active ligand in different oxidation states has been synthesized, including the the iminosemiquinone (isq) 1− compound, Ce( dipp isq) 3 (1-Ceisq), and the amidophenolate (ap) 2− species Ce III ( dipp ap) 3 K 3 (2-Ceap), [Ce III ( dipp ap) 3 K][K(18-c-6)] 2 (2-Ceap 18c6), and [Ce III ( dipp ap) 3 K][K(15-c-5) 2 ] 2 (2-Ceap 15c5). Treating 2-Ceap 15c5 with dioxogen furnishes the cerium(IV) derivative [Ce IV ( dipp ap) 3 ][K(15-c-5) 2 ] 2 (3-Ceap 15c5), and an analogous synthesis can be used to generate [Ce IV ( dipp ap) 3 ][K(crypt)] 2 (3-Ceap crypt). Similarly, addition of hexamethyldisiloxane produces an interesting bis(amidophenolate) species, [(Me 3 SiO) 2 Ce IV ( dipp ap) 2 ][K(15-c-5) 2 ] 2 (4-CeOSiMe 3 ). In conclusion, full spectroscopic and structural characterization of each derivative was performed to establish the oxidation states of both the ligands and the cerium ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Influence of Rare Earth Ce Additions on Microstructure and Mechanical Properties of Experimental Pipeline Steels

Herein, the effect of Ce additions ranging from 57 to 263 ppm is evaluated for an experimental pipeline steel. Compared to the Ce-free steel, progressive Ce additions result in a slightly refined microstructure, significantly improve transverse impact properties, and slightly increase strength. All these observations can be attributed to the gradual transformation of Mn sulfide and Mn–Si–Al oxide inclusions to Ce-containing oxide/sulfides. In particular, the inclusions consist exclusively of sub-5 μm spherical Ce 2 O 2 S particles upon near-stoichiometric additions of Ce, considering the oxygen and sulfur impurity level of the steel. In conclusion, the results suggest that Ce is a potentially promising alloying addition for next-generation pipeline steels by replacing overtly deleterious inclusions with potentially beneficial ones.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Microstructural refinement of an Al-Ce-Mg alloy via Shear Assisted Processing and Extrusion

Al-Ce alloys have attracted recent interest because of their high thermal stability due to the low solubility of Ce in the Al matrix. The Al 11 Ce 3 eutectic phase gives excellent strain hardening behavior and moderate high-temperature strength in the as-cast state. However, its strengthening effect is limited by its coarse as-cast structure. Therefore, alternative manufacturing methods such as additive manufacturing or equal channel angular pressing have been applied to refine the Al 11 Ce 3 phase to good effect. However, these techniques are both expensive and time-consuming. Therefore, this study aims to use Shear Assisted Processing and Extrusion (ShAPE), an emerging solid phase processing technique that is more easily scalable than the previously mentioned methods. ShAPE can produce useful cross-sections of an Al-8Ce-4Mg alloy while refining the Al 11 Ce 3 phase to produce a higher strength material. It was found that a low temperature ShAPE process can improve the room temperature yield strength by ~60 % compared to a binary Al-4Mg alloy. Additionally, the high-temperature yield strength of the Al-Ce alloys increased by 20%, with a simultaneous 15% improvement in ductility compared to the binary Al-Mg alloy. Finally, these results highlight the potential for ShAPE as a processing technique for Al-Ce alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Metal–Oxo Cluster Formation Using Ammonium and Sulfate to Differentiate M IV (Th, U, Ce) Chemistries

Isolating isostructural compounds of tetravalent metals M IV (Zr, Hf, Ce, Th, U, Pu, Np) improves our understanding of metal hydrolysis and coordination behavior across the periodic table. These metals form polynuclear clusters typified by the hexamer [M IV 6 O 4 (OH) 4 ] 12+ . Exploiting the ammonium M IV -sulfate (Ce IV , Th IV , and U IV ) phase space targeting rapid crystallization, we isolate the common hexamer [M IV 6 (OH) 4 (O) 4 ] 12+ but with different numbers of capping sulfates and water molecules for Ce IV , Th IV , and U IV . Furthermore, these phases allowed a direct comparison of bonding trends across the series. Upon cocrystallization with the hexamers, higher complex structures can be identified. Thorium features assemblies with monomer-linked hexamer chains. Uranium features assemblies with sulfate-bridged hexamers and the supramolecular assembly of 14 hexamers into the U 84 , [U 6 (OH) 4 (O) 4 ) 14 (SO 4 ) 120 (H 2 O) 42 ] 72– . Last, cerium showcases the isolation from monomers to the Ce 62 , [Ce 62 (OH) 30 (O) 58 (SO 4 ) 71 (H 2 O) 33.25 ] 41– . Furthermore, small-angle X-ray scattering (room temperature) shows ammonium-induced cluster assembly for Ce IV but minimal reactivity for U IV and Th IV . In this study, because the phases crystallized at elevated temperature demonstrates favorable cluster assembly, these solution phase results were surprising and suggest some other characteristics such as Ce’s facile redox behavior, contributes to its solution-phase speciation.

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

Anisotropic magnetism and Kondo-lattice behavior in the frustrated antiferromagnet Ce 3 ⁢MgBi 5

Here, we report the synthesis and physical characterization of single-crystalline Ce 3 ⁢MgBi 5 , a previously unexplored member of the Ce 3 ⁢𝑀⁢𝑃⁢𝑛 5 family. This compound crystallizes in the hexagonal 𝑃⁢6 3 /𝑚⁢𝑐⁢𝑚 structure, featuring an anisotropic Ce sublattice composed of zigzag chains along the 𝑐 axis and a distorted kagome-like network in the basal plane. Magnetization measurements reveal antiferromagnetic order below 𝑇 𝑁 ≈ 4.2K with strong magnetic anisotropy and multiple field-induced metamagnetic transitions for fields applied perpendicular to [001], leading to a dome-shaped 𝐻–𝑇 phase diagram. Electrical transport exhibits characteristic signatures of a Ce-based Kondo lattice, including broad resistivity maxima and pronounced field-dependent anomalies in the magnetoresistance and Hall response that track the magnetic phase boundaries. Specific-heat measurements confirm the magnetic transition and show that the full R ⁢ln⁡ 2 entropy expected for a Ce 3+ Kramers doublet is recovered by 20 K, indicating an extended temperature range of magnetic fluctuations consistent with Kondo correlations. Our results establish Ce 3 ⁢MgBi 5 as a platform within the Ce 3 ⁢𝑀⁢𝑃⁢𝑛 5 family for exploring the interplay of geometric frustration, magnetic anisotropy, and Kondo-lattice physics under applied magnetic fields.

Kondo effect↗
DOE OSTI2023

$μ$ $\mathrm{SR}$ study of the dipole-octupole quantum spin ice candidate $\mathrm{Ce_2Zr_2O_7}$

The Ce 3+ pseudospin-1/2 degrees of freedom in Ce 2 Zr 2 O 7 possess both dipolar and octupolar character which enables the possibility of novel quantum spin liquid ground states in this material. In this study, we report muon spin relaxation and rotation (μSR) measurements on single-crystal samples of Ce 2 Zr 2 O 7 in zero magnetic field and in magnetic fields directed along the [1, $\overline{1}$, 0] and [1, 1, 1] crystallographic directions, and for magnetic fields directed both longitudinal and transverse to the direction of muon polarization. Our zero-field results show no signs of magnetic ordering or spin freezing, consistent with earlier zero-field μSR measurements on a powder sample of Ce 2 Zr 2 O 7 , and also with the expectations for a quantum spin ice. However, we measure a more gentle relaxation rate for Ce 2 Zr 2 O 7 in zero field at low temperatures than was previously reported. This difference in relaxation rate is likely due to the low oxidation and, correspondingly, the high stoichiometry of our singlecrystal samples. Longitudinal field measurements confirm that the magnetic dipole moments in Ce 2 Zr 2 O 7 remain dynamic at T = 0.1 K on the microsecond timescale. For both [1, $\overline{1}$, 0] and [1, 1, 1] magnetic fields, our μSR Knight shift measurements show a field-induced leveling off of the magnetic susceptibility at low temperature which is qualitatively consistent with corresponding calculations using the numerical-linked-cluster method in combination with recent estimates for the nearest-neighbor exchange parameters of Ce 2 Zr 2 O 7 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗