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Results for “Rare Earth Synthesis”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Data‐Driven Insights into Rare Earth Mineralization: Machine Learning Applications Using Functional Material Synthesis Data

Understanding rare‐earth element (REE) mineralization mechanisms is essential for developing efficient separation strategies. Although the geochemical pathways that generate REE deposits are qualitatively known, quantitative links between specific conditions and mineralization outcomes remain limited. Herein, the repurpose laboratory REE hydrothermal synthesis data—originally collected for functional‐materials fabrication—as a surrogate for studying mineralization with data‐driven methods. The compiled 1,200+ hydrothermal reaction records and trained three machine‐learning models—K‐nearest neighbors (KNN), random forest (RF), and extreme gradient boosting (XGB)—to predict product elements and phases from precursors, additives, reaction conditions, and engineered features. Validation shows XGB achieves the highest accuracy. Feature importance indicates thermodynamic properties of cations and anions dominate model decisions. Correlations reveal positive relationships among precursor concentration, reaction time, pH, and temperature, consistent with classical crystallization behavior. XGB‐based regressors are built to predict crystallization temperature and pH from precursor/product attributes. Performance is strongest when similar training examples exist, while accuracy declines for underrepresented reactions, notably REE carbonates and heavy‐REE systems. Overall, the study shows that functional‐materials datasets can illuminate REE mineralization and provide priors for exploration and processing. Expanding datasets with less‐studied chemistries and conditions will improve generality and support deposit discovery and more efficient REE recovery.

feature importance analysis↗
DOE OSTI2020

Single step solution combustion synthesis of crystalline transuranic-doped rare earth zirconate pyrochlores

One-step solution combustion synthesis (SCS) methods for fabricating durable crystalline transuranic-doped rare earth zirconium pyrochlores are described. Methods are fast, amenable to upscaling, and present a simple strategy for producing crystalline ceramic materials that meet the minimum attractiveness criteria for special nuclear material. The methods include analysis of reactants and reaction conditions to select proper fuel as well as proper fuel content so as to encourage formation of the crystalline product in a single-step synthesis procedure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Solid–state synthesis of multicomponent equiatomic rare–earth oxides

Phase formation in multicomponent rare–earth oxides is determined by a combination of composition, sintering atmosphere, and cooling rate. Polycrystalline ceramics comprising various combinations of Ce, Gd, La, Nd, Pr, Sm, and Y oxides in equiatomic proportions were synthesized using solid–state sintering. The effects of composition, sintering atmosphere, and cooling rate on phase formation were investigated. Single cubic or monoclinic structures were obtained with a slow cooling of 3.3°C/min, confirming that rare–earth oxides follow a different structure stabilization process than transition metal high–entropy oxides. In an oxidizing atmosphere, both Ce and Pr induce a cubic structure, while only Ce plays that role in an inert or reducing atmosphere. Samples without Ce or Pr develop a single monoclinic structure. The structures formed at initial synthesis may be converted to a different one, when the ceramics are annealed in an additional atmosphere. Phase evolution of a five–cation composition was also studied as a function of sintering temperature. In conclusion, the binary oxides used as raw materials completely dissolve into a single cubic structure at 1450°C in air.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Harnessing Biomineralization Potential of Metal-Sequestering Bacteria for Rare Earth Elements (REE) Material Synthesis

Extremophilic methylotrophs, such as Methylotuvimicrobium alcaliphilum 20ZR are known for their natural ability to carry out REE capture and uptake. It has been predicted that proteins associated with surface layers facilitate transport and homeostasis of essential metals. Indeed, electron microscopic analysis coupled with antibody staining revealed that cell envelop of metal-grown M. alcaliphilum 20ZR contains metal-binding proteins in the base of the cup-shaped structures of S-layers. While less explored, the proteins associated with S-layers are also predicted to contribute to scavenging of other minerals essential for core metabolism. Here, we employed bottom-up proteomic study to compare the protein content of S-layer fractions of M. alcaliphilum 20ZR cultures grown in the presence and absence trace metals to identify putative components REE-scavenging machinery.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Synthesis and properties of anhydrous rare-earth phosphates, monazite and xenotime: a review

The synthesis methods, crystal structures, and properties of anhydrous monazite and xenotime (REPO 4 ) crystalline materials are summarized within this review. For both monazite and xenotime, currently available Inorganic Crystal Structure Database data were used to study the effects of incorporating different RE cations on the unit cell parameters, cell volumes, densities, and bond lengths. Domains of monazite-type and xenotime-type structures and other AXO4 compounds (A = RE; X = P, As, V) are discussed with respect to cation sizes. Reported chemical and radiation durabilities are summarized. Different synthesis conditions and chemicals used for single crystals and polycrystalline powders, as well as first-principles calculations of the structures and thermophysical properties of these minerals are also provided.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Cooling-Rate-Driven Polymorphism and Vacancy Ordering in Ce 2 MnGe 6 Intergrowth Phases

Intergrowth phases in intermetallic systems provide a compelling framework for investigating structure–property relationships as a function of crystallographic subunit stacking. In this study, we examine the influence of Mn vacancy ordering on subunit stacking and reassign the structure of Ce 2 MnGe 6 to a monoclinic C2/m space group (a = 8.3486(17) Å, b = 8.6181(18) Å, c = 10.778(2) Å, β = 101.17(2)°). Additionally, we report a monoclinic polymorph of the Ln 2 MGe 6 family characterized as a tripled c-axis supercell derivative of monoclinic Ce 2 MnGe 6 , 3×c-Ce 2 MnGe 6 (a = 8.3482(16) Å, b = 8.6179(18) Å, c = 31.813(6) Å, β = 93.763(7)°). This polymorph emerges under rapid cooling conditions during the synthesis and offers insight into the structural relationship between the orthorhombic and monoclinic variants of the Ln 2 MGe 6 phases. Notably, the supercell form of Ce 2 MnGe 6 (3×c-Ce 2 MnGe 6 ) exhibits increased electrical resistivity and suggests enhanced Zintl-like behavior, potentially indicating greater thermodynamic stability relative to the parent monoclinic phase.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis and Characterization of Homoleptic Rare Earth Nitrato Complexes with the Quaternary Ammonium Cations Et 4 N + and n Pr 4 N +

Two periodic series of homoleptic rare earth nitrato com plexes, [R 4 N] x [M(NO 3 ) y ](M = La-Nd, Sm-Lu, Y); R = Et, $n$ Pr; x = 2-3; y = 5-6) have been synthesized, and charac terized by single crystal X-ray diffraction, IR and Raman spectroscopy, comparing the solid state speciation of the nitrate ions as a function of lanthanide ion and quarternary ammonium cation. The series of the form [Et 4 N] 3 [Ln(NO 3 ) 6 ] crystallizes in the rhombohedral space group $R$$\bar{3}$, as a twelve-coordinate hexanitrato complex [Et 4 N] 3 [Ln(NO 3 ) 6 ] with cocrystallized HNO 3 for La, Pr, and Nd. For Ce, a distinct orthorhombic phase retaining the same formula, [Et 4 N] 3 [Ce(NO 3 ) 6 ] is isolated in the absence of HNO 3 to prevent oxidation of the Ce(III) to Ce(IV) in nitric acid. A ten-coordinate pentanitrato complex, [Et 4 N] 2 [Ln(NO 3 ) 5 ], in monoclinic symmetry forms for the remainder of the series, and for Y(III). The entire series crystallized in the presence of [ $n$ Pr 4 N] + counterions forms a pentanitrato complex [ $n$ Pr 4 N] 2 [M(NO 3 ) 5 ] in the orthorhombic space group, $Pccn$. In conclusion, analysis of trends in the structural and spectroscopic characteristics of these series reveal insight into the structure directing influences of both the lanthanide contraction and the quarternary ammonium cations.

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

Developing techniques for crystal growth synthesis and characterization of rare earth-silicon-germanium magnetoresponsive alloys

In this study, a crystal growth technique was developed for the family of intermetallic, magnetoresponsive RE 5 (Si 1-x Ge x ) 4 alloys in order to access the intrinsic and anisotropic properties. Initial bulk properties measured on polycrystalline samples alluded to the properties being obscured or averaged and high-quality, well-characterized, single crystals would clarify this. Successful crystal growth led to development of oriented sample preparation techniques specific for the crystal structures (monoclinic and orthorhombic) and mechanical properties (hard and brittle) of these alloys, and customized for the various measurement techniques undertaken. Here we describe our journey, sometimes circuitous, from crystal growth to sample preparation and cite the scientific discoveries that came about as a result.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Materials design, synthesis, and transport properties of disordered rare-earth Zintl bismuthides with the anti -Th 3 P 4 structure type

The synthesis, structural elucidation, and transport properties of the extended series Ca 4–x RE x Bi 3 (RE = Y, La–Nd, Sm, Gd–Tm, and Lu; x ≈ 1) and Ca 4–x RE x Bi 3–δ Sb δ (RE = La, Ho, Er, and Lu; x ≈ 1, δ ≈ 1.5) are presented. Structural elucidation is based on single-crystal X-ray diffraction data and confirms the chemical drive of Ca4Bi3 with the cubic anti-Th 3 P 4 structure type (space group I4 ¯3d, no. 220, Z = 4) into a Zintl phase by the introduction of trivalent rare-earth atoms. The structure features complex bonding, heavy elements, and electron count akin to that of valence-precise semiconductors, making it an ideal target for thermoelectrics development. Introducing crystallographic site disorders at the cation site for the Ca 4–x RE x Bi 3 phase and both the cation and anion sites for the Ca 4–x RE x Bi 3–δ Sb δ phase brings about additional desirable characteristics for thermoelectric materials in the context of tuning knobs for lowering thermal conductivity. Electronic structure calculations of idealized Ca 3 YBi 3 and Ca 3 LaBi 3 compounds indicate the opening of indirect bandgaps at the Fermi level with magnitudes Eg = 0.38 eV and 0.57 eV, respectively. The electrical resistivity ρ(T) of some of the investigated phases measured on single crystals evolve in a metallic manner with magnitudes of order 1.4 mΩ cm near 500 K, thus supporting the notion of a degenerate semiconducting state, with the temperature dependence of the Seebeck coefficient α(T) suggesting the p-type behavior. Furthermore, the low electrical resistivity and the realization of a degenerate semiconducting state in the title phases present a window of opportunity for optimizing their carrier concentrations for enhanced thermoelectric performance.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Rare Earth Element Partition Coefficients from Enstatite/Melt Synthesis Experiments

Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb and Lu. The rare earth element concentrations were measured in both the basaltic glass and the enstatite. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. The partition coefficients are consistent with crystal structural constraints.

Schwandt, Craig S.↗
DOE OSTI2021

Synthesis method comparison of compositionally complex rare earth-based Ruddlesden–Popper n = 1 T'-type cuprates

The multicomponent approach has been successfully expanded to the Ruddlesden–Popper structure with the synthesis of two different high-entropy cuprate compositions: (La 0.2 Nd 0.2 Gd 0.2 Tb 0.2 Dy 0.2 ) 2 CuO 4 and (La 0.2 Pr 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 CuO 4 . Additionally, the effect of synthesis method is explored using both solid-state reaction and polymeric steric entrapment (PSE) methods. It is found that PSE leads to more randomly distributed cation species, providing an advantageous method of synthesis for the growing field of high entropy oxides. In situ high-temperature x-ray diffraction tracks the amorphous to crystalline phase transformation in (La 0.2 Nd 0.2 Gd 0.2 Tb 0.2 Dy 0.2 ) 2 CuO 4 powder, synthesized using the PSE method. Using the High-Temperature XRD data, a method for gaining information on the kinetic behavior is also applied. Magnetometry of both compositions indicates ferrimagnetic behavior at low temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Synthesis and characterization of the rare-earth chloride complexes with N,N,N',N' -tetramethylmalonamide

Exploration of the solid-state chemistry of the f-elements and their coordination chemistry can assist in understanding the speciation of these elements in solution, which, in turn, can aid in the interpretation of their chemical behavior in complex liquid-liquid separations. Within these separation processes, malonamides are common organic extractants that are used for complexing both lanthanides and actinides, thus it is relevant to understand the malonamide ligand complexation under various conditions. In this work, we investigate solid-state complexes of the rare-earth chlorides with N,N,N',N' -tetramethylmalonamide (TMMA) across the entire lanthanide series. Here, we isolated two structural families of compounds Ln(TMMA) 2 Cl 3 Ln = La–Dy and [Ln(TMMA) 2 (H 2 O) 4 ]Cl 3 • x H 2 O x = 0,4 Ln = Ho–Lu, showing differences in chloride coordination from the inner-sphere complex for early lanthanides to outer-sphere for the late lanthanides. Both structural series were additionally analyzed by both IR and Raman spectroscopy confirming similarities in malonamide ligand coordination modes, while showing differences in vibrational features associated with chloride and aqua ligand coordination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis of a series of rare-earth-based multi-anion chalcogenide iodides RE 3 Si 2 Se x S 8− x I (RE = La, Ce, Pr, and Nd) using the flux-assisted boron–chalcogen mixture method

Single crystals and polycrystalline powders of rare earth mixed chalcogenide iodides La 3 Si 2 Se 1.21 S 6.79 I, Ce 3 Si 2 Se 1.39 S 6.61 I, Pr 3 Si 2 Se 1.22 S 6.78 I, and Nd 3 Si 2 Se 1.18 S 6.82 I were prepared using the reactive flux-assisted boron–chalcogen mixture (BCM) method at 850 °C. All compounds crystallized in the monoclinic crystal system, space group C2/c (space group number 15). The series adopts the La 3 Si 2 O 8 Cl structure type, containing isolated SiQ 4 tetrahedra connected by REQ 8 (RE = La, Ce, Pr and Nd) polyhedra; this arrangement creates tunnels that are filled by I atoms. The partial substitution of S by Se was carried out to modulate the optical properties. Phase pure samples and uniform solid solutions were obtained for all compositions as determined using powder X-ray diffraction patterns. Polycrystalline powders were used for physical property measurements, including magnetic susceptibility and UV-Vis diffuse reflectance. The solid-state UV-Vis data for the polycrystalline La 3 Si 2 Se 1.21 S 6.79 I, Ce 3 Si 2 Se 1.39 S 6.61 I, and Pr 3 Si 2 Se 1.22 S 6.78 I samples revealed band gaps of E g = 2.5(1), 2.2(1), and 2.3(1) eV, typical of semiconductors. Magnetic measurements indicated that Ce 3 Si 2 Se 1.39 S 6.61 I and Nd 3 Si 2 Se 1.18 S 6.82 I exhibit paramagnetic behavior with slightly negative Weiss constants θ = −25 and −38. The photoluminescence spectrum of Ce 3 Si 2 Se 1.39 S 6.61 I exhibits a broad emission band around ∼493 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Advances in Rare-Earth Tritelluride Quantum Materials: Structure, Properties, and Synthesis

A distinct class of 2D layered quantum materials with the chemical formula of RTe 3 (R = lanthanide) has gained significant attention owing to the occurrence of collective quantum states, superconductivity, charge density waves (CDW), spin density waves, and other advanced quantum properties. To study the Fermi surface nesting driven CDW formation, the layered RTe 3 family stages an excellent low dimensional genre system. In addition to the primary energy gap feature observed at higher energy, optical spectroscopy study on some RTe 3 evidence a second CDW energy gap structure indicating the occurrence of multiple CDW ordering even with light and intermediate RTe 3 compounds. Here, a comprehensive review of the fundamentals of RTe 3 layered tritelluride materials is presented with a special focus on the recent advances made in electronic structure, CDW transition, superconductivity, magnetic properties of these unique quantum materials. A detailed description of successful synthesis routes including the flux method, self-flux method, and CVT along with potential applications is summarized.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ferromagnetism with in-plane magnetization, Dirac spin-gapless semiconducting properties, and tunable topological states in two-dimensional rare-earth metal dinitrides

Since the successful synthesis of bulk single crystals MoN 2 and ReN 2 , which have a layered structure, transition-metal dinitrides have attracted considerable attention in recent years. Here, we focus on rare-earth metal (Rem) elements, and propose seven stable Rem dinitride monolayers with a 1T structure, namely, 1T-RemN 2 . We use first-principles calculations, and find that these monolayers have a ferromagnetic ground state with in-plane magnetization. Without spin-orbit coupling (SOC), the band structures are spin-polarized with Dirac points at the Fermi level. Remarkably, the 1T-LuN 2 monolayer exhibits an isotropic magnetocrystalline anisotropy energy in the xy plane with in-plane magnetization, indicating easy tunability of the magnetization direction. Additionally, when rotating the magnetization vector in the xy plane, we propose a model that accurately describes the variation of the SOC band gap and the two possible topological states (Weyl-like semimetal and Chern insulator states) whose properties are tunable. The Weyl-like semimetal state is a critical point between the two Chern insulator states with opposite sign of the Chern numbers (±1). The nontrivial band gap (up to 60.3 meV) and the Weyl-like semimetal state are promising for applications in spintronic devices.

2-dimensional systems↗
DOE OSTI2020

Infrared optically stimulated luminescence of rare earth doped CaF 2 and co-doped with Al or Li produced by combustion synthesis

The aim of this paper is to characterize the IRSL response of rare earth doped CaF 2 and co-doped with Al or Li, produced by the solution combustion synthesis (SCS). The results showed a high intensity of the infrared optically stimulated luminescence (IRSL) response for the samples of CaF 2 doped with Tb and co-doped with Li. For the samples of CaF 2 doped with Ce and co-doped with Li present better IRSL response than the samples co-doped with Al. It was also observed that the samples of CaF 2 :Ce,Li present a high fading with 50% reduction of the IRSL signal in a period of 60 min. In case of the CaF 2 :Tb,Li there is no significant fading during this period. For clinical dosimetry the fast fading of the dosimeter is not adequate. However, this feature can be exploited for other applications such as tamper-proof passive systems that detect and timestamp the movement of undeclared nuclear materials, by the estimation of the OSL response of materials with different fading rates.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

High-Pressure Synthesis of Bulk Cobalt Cementite, Co 3 C

Transition metal carbides find use in a wide range of advanced high-resilience applications including high-strength steels, heat shields, and deep-earth drills. However, carbides of the mid-to-late transition metals remain difficult to isolate and characterize on account of their metastability, which precludes the preparation of high-quality bulk single crystal samples using traditional solid-state methods. Herein, we report a combined computational and experimental survey of the cobalt-carbon binary system under high pressures and demonstrate that pressure offers a route toward the bulk synthesis of the metastable cementite-type cobalt carbide, Co 3 C, which under ambient conditions can only be prepared in low-dimensional thin film or nanoparticle forms. First-principles calculations reveal two competitive low-energy stoichiometric phases under ambient pressures - Pnnm-Co 2 C (Fe 2 C-type) and Pnma-Co 3 C (Fe 3 Ctype) - consistent with the known low-dimensional phases that have been studied for their promising magnetic properties. However, the calculated formation enthalpy of Pnma-Co 3 C decreases steadily with the applied pressure, while that of Pnnm-Co 2 C increases. Here, we pursue these results using high-pressure laser-heated synthesis methods coupled with in situ X-ray diffraction and observe the formation of Pnma-Co 3 C above 4.8 GPa. We determine the experimental bulk modulus of Co 3 C to be K o = 237 GPa (K p = 4.0). First-principles calculations of the phonon modes in Co 3 C reveal dynamical instabilities at ambient pressure that are absent under compression. These results offer a promising new route for the synthesis of rare-earth-free magnets.

36 MATERIALS SCIENCE↗