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Results for “Rare Earth Compounds”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Integer versus half-integer spin on an approximate honeycomb lattice

Recent interest in honeycomb lattice materials has focused on their potential to host quantum spin liquid (QSL) states. Variations in bond angles and spin allow a range of interesting behaviors on this lattice, from the predicted QSL ground state of the Kitaev model to exotic magnetic orders. Here we report the physical properties of two compounds with rare earths on an approximate honeycomb lattice. Here, the isostructural compounds Nd 2 S 5 Sn (J = 9/2) and Pr 2 S 5 Sn (J = 4) permit a direct comparison of half-integer versus integer spins on this lattice. We find strikingly different magnetic properties for the two compounds. Nd 2 S 5 Sn orders antiferromagnetically at T N ≈ 2.5 K and undergoes several magnetic transitions to other ordered states under applied field. Pr 2 S 5 Sn displays no magnetic ordering transition above T = 0.41 K, and may be proximate to a spin liquid state.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si) 13 -Based Compounds

The transition toward a carbon-neutral society based on renewable energies goes hand in hand with the availability of energy-efficient technologies. Here, magnetocaloric cooling is a very promising refrigeration technology to fulfill this role regarding cryogenic gas liquefaction. However, the current reliance on highly resource critical, heavy rare-earth-based compounds as magnetocaloric material makes global usage unsustainable. Here, we aim to mitigate this limitation through the utilization of a multicaloric cooling concept, which uses the external stimuli of isotropic pressure and magnetic field to tailor and induce magnetostructural phase transitions associated with large caloric effects. In this study, La 0.7 Ce 0.3 Fe 11.6 Si 1.4 is used as a nontoxic, low-cost, low-criticality multiferroic material to explore the potential, challenges, and peculiarities of multicaloric cryocooling, achieving maximum isothermal entropy changes up to −28 J (kg K) −1 in the temperature range from 190 K down to 30 K. Thus, the multicaloric cooling approach offers an additional degree of freedom to tailor the phase transition properties and may lead to energy-efficient and environmentally friendly gas liquefaction based on designed-for-purpose, noncritical multiferroic materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Crystalline compounds for remediation of rare-earth fission products: A review

Rare-earth (RE) containing crystals have been investigated as media for the immobilization of RE fission products. During reprocessing of spent nuclear fuels, various fission products including REs, alkalis, and alkaline earths are found after the extraction of actinides. One viable option to immobilize the RE fission products is to incorporate them into chemically durable crystalline phases in specific waste forms. This study summarizes the crystal structures and synthesis methods of six RE-containing compounds that have applications in remediation of RE fission products. These compounds include oxyapatite [Ca2RE8(SiO4)6O2], oxychloride [REOCl], borosilicate [RE3BSi2O10], pyrochlore [RE2A2O7], monazite [REPO4], and perovskite [REAO3] where A denotes transitional metals. This review provides an overview of literature on the usage of these six compounds for immobilizing RE fission products and summarizes different synthesis methods for producing these compounds. Comparisons of structural parameters with different REs in each compound are also discussed.

rare-earth oxychloride, rare-earth oxyapatite, rar↗
DOE OSTI2022

Spin liquid state in a rare-earth hyperkagome lattice

We report quantum fluctuations enhanced by frustration and subtle interplay between competing degrees of freedom offer an ideal ground to realize novel states with fractional quantum numbers in quantum materials that defy standard theoretical paradigms. Quantum spin liquid (QSL) is a highly entangled state wherein frustration-induced strong quantum fluctuations preclude symmetry-breaking phase transitions down to zero temperature without any order parameter. Experimental realizations of QSL in quantum materials with spin dimensionality greater than one is very rare. Here, we present our thermodynamic, nuclear magnetic resonance, muon spin relaxation, and inelastic neutron scattering studies of a rare-earth hyperkagome compound Li 3 Yb 3 Te 2 O 12 in which Yb 3+ ions constitute a three-dimensional spin lattice without any detectable disorder. Our comprehensive experiments evince neither signature of magnetic ordering nor spin freezing down to 38 mK that suggest the realization of dynamic liquid-like ground state in this antiferromagnet. The ground state of this material is interpreted by a low energy J eff = 1/2 degrees of freedom with short-range spin correlations. The present results demonstrate a viable basis to explore spin-orbit driven enigmatic correlated quantum states in a class of rare-earth-based three-dimensional frustrated magnets that may open avenues in theoretical and experimental search for spin liquids.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Magnetic transitions and magnetocaloric effect of Gd 4 Nd 1 Si 2 Ge 2

In this work, crystal structure and magnetic properties of the quaternary Gd 4 Nd 1 Si 2 Ge 2 compound were investigated using synchrotron X-ray diffraction and magnetic measurements. The compound crystallized into an orthorhombic structure in the temperature range 200-300 K. In zero field cooling, the compound undergoes a spin reorientation following a ferromagnetic-like transition at 276 K. The spin reorientation is hinted at by nonlinear changes of lattice parameters but is suppressed in a high magnetic field of 6 T. Magnetic measurements revealed a magnetocaloric effect with a high relative cooling power. It is suggested that Nd substitution for Gd enlarges magnetic anisotropy and induces a canted spin structure.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Semihard magnetic properties of TiFe 2.5 iron-rich Laves phase and the effect of 4d- and 5d-element-substitutions for Ti

Rare-earth-free compounds exhibiting modest intrinsic hard magnetic properties may still yield viable permanent magnets if their constituent elements are abundant and inexpensive, and the properties are at least comparable to those of the hard ferrites. In this study, one such compound, the off-stoichiometric TiFe 2.5 Laves phase with the hexagonal C14 crystal structure, was found to exhibit – in addition to the already known room-temperature ferromagnetism – a uniaxial, albeit weak, magnetic anisotropy. With a Curie temperature of 422 K, saturation magnetization of 55.3 Am 2 /kg and magnetic hardness parameter of 0.97 this semihard compound is just below the threshold for being of interest for the development into permanent magnets. Replacing a small fraction of Ti with the 4d Nb and Mo or with the 5d Ta or W increases the anisotropy field, but only below room temperature. Replacing Ti with Zr or Hf increases the Curie temperature and leads to a spin reorientation below 200 K. All these substitutions, as well as combined (Zr,W) and (Nb,W) substitutions, fail to improve the room-temperature intrinsic hard magnetic properties of the Fe-rich Laves phase. Furthermore, an attempt to develop a room-temperature coercivity through high-energy ball-milling yielded a value of 0.026 T, an unusually small 2.9% fraction of the anisotropy field. Here, defects inherent in the C14 crystal lattice may be responsible for the underperformance.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Structurally Defined Water‐Soluble Metallofullerene Derivatives towards Biomedical Applications

Abstract Endohedral metallofullerenes (EMFs) are excellent carriers of rare‐earth element (REE) ions in biomedical applications because they preclude the release of toxic metal ions. However, existing approaches to synthesize water‐soluble EMF derivatives yield mixtures that inhibit precise drug design. Here we report the synthesis of metallobuckytrio (MBT), a three‐buckyball system, as a modular platform to develop structurally defined water‐soluble EMF derivatives with ligands by choice. Demonstrated with PEG ligands, the resulting water‐soluble MBTs show superb biocompatibility. The Gd MBTs exhibit superior T 1 relaxivity than typical Gd complexes, potentially superseding current clinical MRI contrast agents in both safety and efficiency. The Lu MBTs generated reactive oxygen species upon light irradiation, showing promise as photosensitizers. With their modular nature to incorporate other ligands, we anticipate the MBT platform to open new paths towards bio‐specific REE drugs.

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

Magnetothermal properties of Tm x Dy 1- x Al 2 ( x = 0.25, 0.50 and 0.75)

Here, we describe magnetic, thermal, and magnetocaloric properties of rare earth intermetallic compounds Tm x Dy 1-x Al 2 with 0.25, 0.5 and 0.75. Using model Hamiltonian we consider contributions of the crystalline electric field anisotropy in both Tm and Dy magnetic sublattices, disorder in exchange interactions among Tm-Tm, Dy-Dy and Tm-Dy magnetic ions, and the Zeeman effect. Employing earlier reported and new experimental measurements, we first determine a single free variable – the intersublattice magnetic exchange parameter – to properly model the temperature and magnetic field dependencies of heat capacity and magnetization, and then use the modeling results to explain the emergence of an anomalous spin reorientation transition and its influence on the magnetocaloric effect in the title compounds. Theoretical results agree with experimental data reasonably well.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Hidden first-order phase transitions and large magnetocaloric effects in GdNi 1-x Co x

We report a large magnetocaloric effect tunable between 70 and 115 K in a series of rare earth intermetallic compounds GdNi 1-x Co x with x varying from 0 to 0.15 that manifest rather unconventional second-order phase transitions with concurrent changes in both magnetic and crystallographic sublattices. While the Curie temperature, TC, linearly increases with x(Co), the maximum isothermal entropy change induced by magnetic field varying between 0 and 50 kOe slightly decreases from 14 J/kg K at 71 K when x(Co) = 0 to10 J/kg K at 115 K when x(Co) = 0.15. Additionally, the temperature-averaged entropy change figures of merit calculated at temperature spans of 10 K for all examined compositions are comparable to those of the best known magnetocaloric materials that exhibit second-order phase transitions, including elemental Gd and La(Fe,Co,Si) 13 alloys. Through a detailed analysis of the magnetic field-induced entropy changes along with assessment of critical exponents we explore the role magneto-elastic coupling plays in controlling magnetocaloric properties of GdNi 1-x Co x compounds. We also formulate a model based on the mean field theory approximation to describe both magnetic and magnetocaloric properties of the title materials in qualitative agreement with experimental results.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nanoengineering room temperature ferroelectricity into orthorhombic SmMnO 3 films

Orthorhombic R MnO 3 ( R = rare-earth cation) compounds are type-II multiferroics induced by inversion-symmetry-breaking of spin order. They hold promise for magneto-electric devices. However, no spontaneous room-temperature ferroic property has been observed to date in orthorhombic R MnO 3 . Here, using 3D straining in nanocomposite films of (SmMnO 3 ) 0.5 ((Bi,Sm) 2 O 3 ) 0.5 , we demonstrate room temperature ferroelectricity and ferromagnetism with T C,FM ~ 90 K, matching exactly with theoretical predictions for the induced strain levels. Large in-plane compressive and out-of-plane tensile strains (-3.6% and +4.9%, respectively) were induced by the stiff (Bi,Sm) 2 O 3 nanopillars embedded. The room temperature electric polarization is comparable to other spin-driven ferroelectric R MnO 3 films. Also, while bulk SmMnO 3 is antiferromagnetic, ferromagnetism was induced in the composite films. The Mn-O bond angles and lengths determined from density functional theory explain the origin of the ferroelectricity, i.e. modification of the exchange coupling. Our structural tuning method gives a route to designing multiferroics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Determination of single-crystal elastic moduli of Li RE F 4 ( RE =Y, Gd, and Tb) by resonant ultrasound spectroscopy

The tetragonal fluoro-scheelite Li RE F 4 compounds (RE = rare earth) have been shown to exhibit a variety of useful optical and magnetic properties. While LiYF 4 has been widely studied, many of the fundamental thermodynamic properties of other members of this family remain unknown. Here, we report the complete elastic tensors (C ij ) of single-crystalline LiYF 4 , LiTbF 4 , and LiGdF 4 using resonant ultrasound spectroscopy and density functional theory (DFT). Here we compare the results for LiYF 4 with prior experimental results using time-of-flight ultrasound methods. This is the first report, however, of the experimental elastic tensors of LiTbF 4 and LiGdF 4 . The present results point to a softening of the elastic moduli of the Li RE F 4 system when Y is replaced by the larger ionic radius of Tb or Gd. Furthermore, we find that just 0.3% doping with Nd on the Y site also leads to a slight softening of the moduli. The variation of the elastic moduli as a function of temperature up to 216°C was also measured. A nearly linear softening of all seven independent elastic moduli was observed with increasing temperature. Phonon dispersions and phonon density of states obtained by DFT support the experimental finding of a significantly higher sound velocity due to lighter Y atoms in LiYF 4 , as compared to heavier LiTbF 4 and LiGdF 4 .

36 MATERIALS SCIENCE↗
DOE OSTI2022

Unusual first-order magnetic phase transition and large magnetocaloric effect in Nd 2 In

A large magnetocaloric effect with its maximum near the boiling point of natural gas occurs in a rare-earth intermetallic compound Nd 2 In. While behaviors of physical properties indicate that paramagnetic-ferromagnetic transformation supporting the large magnetocaloric effect is firstorder in nature, temperature dependent crystallographic study reveals no changes in lattice symmetry and lack of discontinuities either in phase volume or lattice parameters. In this work we discuss how the borderline first-order nature of phase transformation in Nd 2 In is markedly different from conventional firstorder magnetic transitions occurring in other members of the family – isostructural Pr 2 In and non-isostructural Eu 2 In.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Production of castable light rare earth rich light metal compositions from direct reduction processes

The disclosure concerns methods for making a composition comprising a light metal and an intermetallic comprising the light metal and a light rare earth element. The composition also may include a plurality of nanoparticles comprising an oxide of the light metal. The method includes directly reducing a light rare earth element precursor compound in a melt of the light metal, thereby forming the light rare earth element and nanoparticles of the light metal oxide.

Rios, Orlando↗
DOE OSTI2021

Crystal and Magnetic Structures of the Ternary Ho 2 Ni 0.8 Si 1.2 and Ho 2 Ni 0.8 Ge 1.2 Compounds: An Example of Intermetallics Crystallizing with the Zr 2 Ni 1–x P Prototype

We report two new rare-earth (R) ternary intermetallic compounds—Ho 2 Ni 0.8 T 1.2 with T = Si and Ge—that correspond to the R 5 Ni 2 T 3 phase earlier reported to form in Dy–Ni–T and Ho–Ni–T ternary systems. The compounds crystallize in a filled version of the orthorhombic Zr 2 Ni 1–x P-type structure with x = 0.52; their stoichiometry, determined from both single-crystal and powder X-ray diffraction data, is centered on Ho 2 Ni 0.8 T 1.2 with a narrow solid solubility range for the silicide, while the germanide appears to be a line phase. In addition to R = Dy and Ho, R 2 Ni 0.8 T 1.2 compounds also form for R = Y and Tb, representing the first examples of rare-earth-based compounds adopting the Zr 2 Ni 1–x P structural prototype. Bulk magnetization data reveal the main transitions of the ferrimagnetic or ferromagnetic type at TC = 38 K for Ho 2 Ni 0.8 Si 1.2 and TC = 37 K for Ho 2 Ni 0.8 Ge 1.2 , which are followed by subsequent magnetic reordering at lower temperatures. Neutron diffraction shows complex magnetic structures below T C with both ferromagnetic and antiferromagnetic components and magnetic propagation vector κ 1 = [0, 0, 0]. Below T N ≅ 24 K (22 K) for the silicide (germanide), an additional antiferromagnetic coupling following an incommensurate magnetic propagation vector κ 2 = [κ x , 0, 0] appears to coexist with the first magnetic structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Selective Sulfidation for Rare Earth Element Separation

Rare earth metals and compounds are critical components of advanced materials for energy, structural alloys, and transportation. These low-tonnage elements are sourced together as by- and co-products, and presently require complete hydrometallurgical dissolution followed by liquid–liquid separation for their isola- tion and production. There is great interest in developing alternatives to those hydrometallurgical processes in order to limit the environmental impact of rare earth element supply. Herein, we present selective sulfidation as a novel, high- temperature alternative to facilitate physical separation of rare earth by- and co- product elements. We explore the thermodynamics of rare earth oxide sulfidation with elemental sulfur, and discuss the role of carbon in controlling sulfidation selectivity. We apply these findings to the demonstration of selective sulfidation for iron-rare earth and lanthanide-lanthanide separations.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electronic Structure and Spin Correlations in Novel Magnetic Structures

The research has advanced understanding of the interrelation between the crystal structure and magnetism in several materials which are or can be of interest for the development of improved, specialized or more cost-effective permanent magnets, as well as in selected materials for biomedical and catalytic applications. Fundamental aspects of ferromagnetism were investigated for Mn-Ge, Co-V and Co-Ge nanoclusters and for melt-spun Co-Sn alloys. New solution-chemistry synthesis methods were designed and tested for Fe-Pt, Fe3C and Fe3O4 nanoparticles. Off-stoichiometric Laves phases in the Fe-Si-Zr, Fe-Nb and Fe-Ta systems, as well as Fe5(Si,Ge)B2 compounds were assessed as new rare-earth-free permanent magnet materials; all except the Fe-Si-Zr Laves phases were found to be promising enough to merit a further exploration. A new method for manufacturing rare-earth-free magnets based on the MnBi compound was developed; by purposely avoiding oxidation-sensitive fine single-crystalline powders, the new method yields magnets with a 50% larger energy storage capacity. Studies of rare-earth-lean permanent-magnet materials (lean compared to the currently predominant Nd-Fe-B materials) were focused on the tetragonal compound of the ThMn12 structure type and included both discovery and characterization of new formulations and exploration of new fabrication/processing techniques. Among the most significant achievements were successful preparation of a vanadium-lean SmFe11V compound, the first observation of thermomechanically induced texture in nanocrystalline Sm(Fe,V)12 alloys, and a breakthrough reduction-diffusion synthesis of Sm1-xZrx(Fe0.8Co0.2)11.2Ti0.8 single-crystal particles with a coercivity as high as 12.6 kOe. Several experiments aimed at improvement of the Nd-Fe-B magnet have also been undertaken including a five-fold increase of the coercivity through a grain-boundary diffusion treatment of a Nd10Fe84B6 nanocrystalline alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Methods of recovering rare earth elements

A method of recovering a rare earth element. The method comprises dissolving a rare earth element magnetic material in a dissolution organic solvent and a β-diketone compound to form a dissolved rare earth element mixture. A rare earth element of the rare earth element magnetic material and the β-diketone compound are reacted to form a β-diketonate chelate complex and the dissolution organic solvent is removed. The β-diketonate chelate complex is removed using a separation organic solvent, and the β-diketonate chelate complex is recovered. Additional methods are also disclosed.

Klaehn, John R.↗
DOE OSTI2020

Electronic structure of the parent compound of superconducting infinite-layer nickelates

The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO 2 has strengthened these efforts. In this work, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO 2 and NdNiO 2 , while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with $3d_{x^2-y^2}$ symmetry in the NiO 2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics which are well known for heavy fermion behaviour, where the NiO 2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like ‘oxide-intermetallic’ replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗