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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Multiscale and Multimodal Characterization of 2D Titanium Carbonitride MXene

Here, a comprehensive study on the prototype solid solution phase carbonitride MXene Ti 3 CN is conducted using nuclear magnetic resonance, electron spin resonance, total and quasi-elastic neutron scattering, combined with density functional theory-based electronic structure and molecular dynamic calculations. The combination of experiment and theory lead toward rational atomic structural models of Ti 3 CN. The remnant Al ions from the etching process significantly tune the interlayer spacing, distinct from the more typical MXene, Ti 3 C 2 , prepared similarly. Neutron scattering indicates the surface terminations of Ti 3 CN display high oxygen and fluorine concentrations and rather low hydroxyl and hydrogen concentrations. Calculations show that the structure including both the residual Al ions and mixed surface terminations give the best agreement with the measurements. The water molecules in Ti 3 CN are highly immobile, in strong contrast to those in Ti 3 C 2 . The analysis of the electronic structure suggests that the nitride MXene displays higher conductivity than the carbides. Finally, the absence of hydroxyl groups in terminations, the solid-solution in the anion sites, the remnants within layers, and immobile water altogether make the carbonitrides a unique series in the MXene family, implying a further exploration of their exotic properties and applications in energy storage.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

Herbell, T. P.↗
NASA NTRS1985

Electrical conductivity and phase diagram of binary alloys. 21: The system palladium-chromium

Pd-Cr alloys were investigated by thermal analysis, hardness measurements, X-ray analysis, microscopic examination of etched pieces, and temperature-resistance curves of the solid alloys. Only one compound, Pd2Cr3, m, 1389 deg, is formed. It possesses a cubic face centered lattice and forms with excess Pd a series of solid solutions with a minimum m.p. at 45 atoms% Pd. Hardness maximum appears at the Pd2Cr3 point. Pd2Cr3 forms no solid solutions with Cr but eutectic point appears at 25 atoms% Pd, m. 1320 deg. The sp. resistance of pure Cr in an atom of H, indicates no allotropic forms. Cr2O3 is solid in molten Cr. Pure Cr melts at 1890 plus or minus 10 deg but Cr contg. Cr2O3 starts to melt at 1770 to 1790 deg.

Grube, G.↗
DOE OSTI2025

HfZr_BCC_SolidSolution_128atoms_VASP6

We performed density functional theory (DFT) calculations for body-centered-cubic (BCC) structures with 128 lattices sites of solid solution binary alloys hafnium-zirconium (Hf-Zr). The electronic structures of alloys have been calculated using Vienna Ab initio Simulation Package (VASP). Within this package the DFT approach is used to reduce many-body Schrodinger equation to set of single particle Kohn-Sham (KS) equations. The generalized electronic exchange-correlation functional is described by generalized gradient approximation with the Perdew-Burke-Ernzerhof parametrization. The electron-ion interactions is described by pseudopotentials developed within the plane-wave basis projector augmented-wave (PAW) approach. These pseudopotentials are available at the VASP portal (http://cms.mpi.univie.ac.at/vasp/). Our calculations have been run with the pseudopotentials treating s and p semi-core states as valence in case for the elements Hf and Zr. The electronic densities and potentials are expanded over plane-waves with energy cutoff of 350 eV. 2x2x2 k-mesh and normal precision were used. The alloys were modeled by supercell containing 128 randomly distributed atoms. At initial step the atoms occupy perfect bcc lattice cites. This initial structure was optimized until energy changes less than 1e-6 eV, while forces acting on atoms don't exceed 1e-2 eV/angstrom. The electron-ion interaction is described by PAW pseudopotentials. The calculations have been collected by sampling chemical compositions across the entire compositional range. The chemical compositions have been sampled by progressively changing the number of atoms per constituent by 4. For each chemical composition of binaries and ternaries, the first-principle calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. We collected data for a total of 3,100 randomized atomic structures over 31 chemical compositions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

HfTa_BCC_SolidSolution_128atoms_VASP6

We performed density functional theory (DFT) calculations for body-centered-cubic (BCC) structures with 128 lattices sites of solid solution binary alloys hafnium-tantalum (Hf-Ta). The electronic structures of alloys have been calculated using Vienna Ab initio Simulation Package (VASP). Within this package the DFT approach is used to reduce many-body Schrodinger equation to set of single particle Kohn-Sham (KS) equations. The generalized electronic exchange-correlation functional is described by generalized gradient approximation with the Perdew-Burke-Ernzerhof parametrization. The electron-ion interactions is described by pseudopotentials developed within the plane-wave basis projector augmented-wave (PAW) approach. These pseudopotentials are available at the VASP portal (http://cms.mpi.univie.ac.at/vasp/). Our calculations have been run with the pseudopotentials treating s and p semi-core states as valence in case for the elements Hf and Ta. The electronic densities and potentials are expanded over plane-waves with energy cutoff of 350 eV. 2x2x2 k-mesh and normal precision were used. The alloys were modeled by supercell containing 128 randomly distributed atoms. At initial step the atoms occupy perfect BCC lattice sites. This initial structure was optimized until energy changes less than 1e-6 eV, while forces acting on atoms don't exceed 1e-2 eV/angstrom. The electron-ion interaction is described by PAW pseudopotentials. The calculations have been collected by sampling chemical compositions across the entire compositional range. The chemical compositions have been sampled by progressively changing the number of atoms per constituent by 4. For each chemical composition of binaries and ternaries, the first-principle calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. We collected data for a total of 3,040 randomized atomic structures over 31 chemical compositions. Further methodological and structural information is contained in the dataset README.txt file.

36 MATERIALS SCIENCE↗
DOE OSTI2026

TiV_BCC_SolidSolution_128atoms_VASP6

We performed density functional theory (DFT) calculations for body-centered-cubic (BCC) structures with 128 lattices sites of solid solution binary alloys titanium-vanadium (Ti-V). The electronic structures of alloys have been calculated using Vienna Ab initio Simulation Package (VASP). Within this package the DFT approach is used to reduce many-body Schrodinger equation to set of single particle Kohn-Sham (KS) equations. The generalized electronic exchange-correlation functional is described by generalized gradient approximation with the Perdew-Burke-Ernzerhof parametrization. The electron-ion interactions is described by pseudopotentials developed within the plane-wave basis projector augmented-wave (PAW) approach. These pseudopotentials are available at the VASP portal (http://cms.mpi.univie.ac.at/vasp/). Our calculations have been run with the pseudopotentials treating s and p semi-core states as valence in case for the elements Ti and V. The electronic densities and potentials are expanded over plane-waves with energy cutoff of 350 eV. 2x2x2 k-mesh and normal precision were used. The alloys were modeled by supercell containing 128 randomly distributed atoms. At initial step the atoms occupy perfect bcc lattice cites. This initial structure was optimized until energy changes less than 1e-6 eV, while forces acting on atoms don't exceed 1e-2 eV/angstrom. The electron-ion interaction is described by PAW pseudopotentials. The calculations have been collected by sampling chemical compositions across the entire compositional range. The chemical compositions have been sampled by progressively changing the number of atoms per constituent by 4. For each chemical composition of binaries and ternaries, the first-principle calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. We collected data for a total of 3,100 randomized atomic structures over 31 chemical compositions. The calculations have been collected on Air Force HPC11 cluster using the VASP 6.5.1. Additional methodology and file structure information is available in the dataset README.txt file.

36 MATERIALS SCIENCE↗
DOE OSTI2026

NbTi_BCC_SolidSolution_128atoms_VASP6

We performed density functional theory (DFT) calculations for body-centered-cubic (BCC) structures with 128 lattices sites of solid solution binary alloys niobium-titanium (Nb-Ti). The electronic structures of alloys have been calculated using Vienna Ab initio Simulation Package (VASP), https://github.com/ORNL/ScalableWorkflow_VASP_Calculations. Within this package the DFT approach is used to reduce many-body Schrodinger equation to set of single particle Kohn-Sham (KS) equations. The generalized electronic exchange-correlation functional is described by generalized gradient approximation with the Perdew-Burke-Ernzerhof parametrization. The electron-ion interactions is described by pseudopotentials developed within the plane-wave basis projector augmented-wave (PAW) approach. These pseudopotentials are available at the VASP portal (http://cms.mpi.univie.ac.at/vasp/). Our calculations have been run with the pseudopotentials treating s and p semi-core states as valence in case for the elements Nb and Ti. The electronic densities and potentials are expanded over plane-waves with energy cutoff of 350 eV. 2x2x2 k-mesh and normal precision were used. The alloys were modeled by supercell containing 128 randomly distributed atoms. At initial step the atoms occupy perfect bcc lattice cites. This initial structure was optimized until energy changes less than 1e-6 eV, while forces acting on atoms don't exceed 1e-2 eV/angstrom. The electron-ion interaction is described by PAW pseudopotentials. The calculations have been collected by sampling chemical compositions across the entire compositional range. The chemical compositions have been sampled by progressively changing the number of atoms per constituent by 4. For each chemical composition of binaries and ternaries, the first-principle calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. We collected data for a total of 3,100 randomized atomic structures over 31 chemical compositions. The calculations have been collected on Air Force HPC11 cluster using the VASP 6.5.1. Additional methodology and file structure information is available in the dataset README.txt file.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Insights into palladium poisoning of Cu/SSZ-13 selective catalytic reduction catalysts

Here, the impacts of Pd poisoning to the activity, selectivity, and hydrothermal stability of Cu/SSZ-13 selective catalytic reduction (SCR) catalysts are reported. Pd lowers DeNOx efficiency of Cu/SSZ-13 via two mechanisms: (1) displacing SCR active sites in the form of isolated Pd-ions, and (2) catalyzing non-selective NH 3 oxidation in the form of PdO. The first mechanism works by the diffusion of isolated Pd-ions into chabazite cages to displace ZCu II OH SCR active species, and it occurs on Cu/SSZ-13 catalysts with and without external surface CuO clusters in similar fashion. In contrast, the second mechanism works differently with and without external surface CuO clusters. For Cu/SSZ-13 catalyst without external CuO clusters (i.e., primarily isolated Cu-ions), PdO leads to significant decrease of DeNOx efficiency at reaction temperatures above ~400°C due to its non-selective NH 3 oxidation activity at high temperatures. However, this poisoning effect becomes much less impactful on Cu/SSZ-13 catalyst containing CuO clusters. This is due to the formation of CuO-PdO solid solution via interactions between CuO and PdO, which reduces non-selective NH 3 oxidation potential. Furthermore, this solid solution formation even mitigates adverse effects caused by hydrothermal aging. Hence, the poisoning effects of Pd are closely related to Cu speciation and spatial distribution of a Cu/SSZ-13 catalyst. Finally, this study suggests a strategy in eliminating Pd poisoning, that is, the introduction of an oxide phase that effectively traps PdO but does not adversely influence SCR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1997

Development of Creep-Resistant NiAl(Ti,Hf) Single-Crystal Alloys

Nickel-base superalloys are the current choice for high-temperature jet engine applications such as turbine blades and vanes. However, after more than five decades of use, nickel-base superalloys have reached their limit, since the operating temperatures in gas turbine engines are now approaching the melting temperature of these alloys. Thus alternative materials, such as lightweight NiAl intermetallic alloys with superior properties, (e.g., high melting temperature, high thermal conductivity, and excellent chemical stability and oxidation resistance) are required for the next generation of high-temperature structural materials for more efficient 21st century civil transport systems. The two major disadvantages that have historically prevented the application of NiAl as a high-temperature structural material are its poor creep resistance and low room-temperature ductility. Alloying strategies similar to those used for nickel-base superalloys are being used to improve the high-temperature strength via solid-solution and precipitate-hardening effects. This study highlights the potent role of Ti and Hf as potential solid-solution strengtheners in NiAl and also the added effect of second-phase particles when Ti and Hf are both used.

Source record↗
DOE OSTI2020

Enhanced activity and stability of MgO-promoted Ni/Al 2 O 3 catalyst for dry reforming of methane: Role of MgO

Highly dispersed nickel nanoparticles (NPs) were deposited on Al 2 O 3 NPs by atomic layer deposition (ALD). Various amounts of MgO were loaded on Ni/Al 2 O 3 catalysts by the incipient wetness (IW) method for dry reforming of methane. Fresh and used catalysts were systematically characterized to reveal the effects of MgO on the catalytic performance. MgO was found to increase the basic amount and basic strength of catalyst surfaces, which provided additional surface oxygen species and assisted the adsorption and activation of CO 2 . Although the formation of NiO-MgO solid solution, during the calcination of incipient wetness, did not improve the overall reducibility, the Ni NPs from NiO-MgO solid solution after reduction formed an intimate interaction with MgO, which could inhibit Ni NPs from sintering and provide sufficient metal-support interface for CO 2 activation. The MgO-promoted Ni/Al 2 O 3 reached a methane reforming rate of 1780 L CH4 g Ni -1 h -1 at 850 °C, which is 26% more than that of the pristine Ni/Al 2 O 3 . Finally, the higher CO 2 activity enhanced the oxidation rate of the surface carbon generated from side-reactions, thereby resulting in a higher reforming rate and inhibiting coke formation, especially the detrimental graphitic encapsulating carbon on the active nickel surface.

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

Development of Novel Ferritic-Martensitic Steels with Superior Creep Properties for Power Plant Applications

A creep resistant martensitic steel, CPJ-7, was developed with an operating temperature approaching 650°C. Subsequently, another creep resistant martensitic steel, JMP, was designed with the potential to operate at, or slightly above, 650°C. This report describes the development of these alloys from early iterations of CPJ steels to the final CPJ-7 formulation as well as the more heat resistant JMP steel formulation. The design originated from computational modeling for phase stability and precipitate strengthening using fifteen constituent elements. Approximately forty heats of CPJ and ten of JMP, each weighing ~7 kg, were vacuum induction melted. A computationally optimized heat treatment schedule was developed to homogenize the ingots prior to hot forging and rolling prior to final normalization and tempering. Overall, wrought and cast versions of CPJ-7 present superior creep properties when compared to wrought and cast versions of COST alloys for steam turbine and wrought and cast versions of P91/92 for boiler applications. For instance, the Larson Miller Parameter curve for CPJ-7 at 650°C almost coincides with that of COST E at 620°C. The prolonged creep life was attributed to slowing down the process of the destabilization of the MX and M 23 C 6 precipitates at 650°C. On the other hand, the cast version of CPJ-7 also revealed superior mechanical performance, well above commercially available cast 9% Cr martensitic steel or derivatives, especially for creep life at 650°C. The casting process employed slow cooling to simulate the conditions of a thick wall full-size steam turbine casing but utilized a separate homogenization step prior to final normalization and tempering. To advance the development of CPJ-7 for commercial applications, a process was used to scale up the production of the alloy using vacuum induction melting (VIM) and electroslag remelting (ESR), which underlined the importance of melt processing control of intentionally designed minor and trace elements in these advanced alloys. Following the work on CPJ-7, the JMP steels were designed with higher Co for increased solid solution strengthening, Si for oxidation resistance and increased W (with low Mo content) for matrix strength and stability as well as solid solution strengthening. The JMP steels showed increases in creep life compared to CPJ-7 between 118 to 150% at 650°C for testing at various stresses between 138 MPa and 207 MPa. On a Larson-Miller plot, the performance of the JMP steels surpasses that of state-of-the-art MARBN and other MARBN-type steels. The influence of various elements within the composition of the alloys on the microstructure and mechanical properties are discussed. This report presents approximately 420,000 h of in-house creep testing, the equivalent of almost 50 years of cumulative creep tests.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Potential Dependent Mn Oxidation and Its Role in Passivation of Ni 38 Fe 20 Cr 22 Mn 10 Co 10 Multi-Principal Element Alloy Using Multi-Element Resolved Atomic Emission Spectroelectrochemistry

The identity of passivating oxides on multi-principal element alloys is of great interest as their optimization offers the potential for exceptional corrosion resistance in aqueous solutions over a broad range of potential and pH. This study focuses on a non-equiatomic Ni 38 Fe 20 Cr 22 Mn 10 Co 10 solid solution alloy and tracks the fate of each alloying element during linear sweep voltammetry, low and intermediate potential holds in the passive potential domain as well as during open circuit relaxation after anodic polarization in slightly acidified Cl − solution. Ni dissolves at all potentials investigated in this work, Fe and Co are incorporated into oxides or hydroxides in low concentrations whilst Cr and Mn are enriched at passive potentials. At low passivating potentials, Mn(II) dissolves and is incorporated in minor amounts in oxides containing large concentrations of Cr(III). Considerable enrichment in Mn(II)-species occurs relative to Cr(III) in the oxide at 0.1 V vs SCE. Electrochemical impedance spectroscopy suggests the presence of layered oxides with marginal passivation at high Mn(II) levels. The formation of these oxides depends on a combination of thermodynamic and kinetic factors as well as the sequence of passivation.

Han, Junsoo (ORCID:0000000192952954)↗
DOE OSTI2024

Structural Evolution and Photoluminescence Quenching across the FASnI 3– x Br x ( x = 0–3) Perovskites

One of the primary methods for band gap tuning in metal halide perovskites has been halide (I/Br) mixing. Despite widespread usage of this type of chemical substitution in perovskite photovoltaics, there is still little understanding of the structural impacts of halide alloying, with the assumption being the formation of ideal solid solutions. The FASnI 3–x Br x (x = 0–3) family of compounds provides the first example where the assumption breaks down, as the composition space is broken into two unique regimes (x = 0–2.9; x = 2.9–3) based on their average structure with the former having a 3D and the latter having an extended 3D (pseudo 0D) structure. Pair distribution function (PDF) analyses further suggest a dynamic 5s 2 lone pair expression resulting in increasing levels of off-centering of the central Sn as the Br concentration is increased. These antiferroelectric distortions indicate that even the x = 0–2.9 phase space behaves as a nonideal solid-solution on a more local scale. Solid-state NMR confirms the difference in local structure yielding greater insight into the chemical nature and local distributions of the FA + cation. In contrast to the FAPbI 3–x Br x series, a drastic photoluminescence (PL) quenching is observed with x ≥ 1.9 compounds having no observable PL. In conclusion, our detailed studies attribute this quenching to structural transitions induced by the distortions of the [SnBr 6 ] octahedra in response to stereochemically expressed lone pairs of electrons. This is confirmed through density functional theory, having a direct impact on the electronic structure.

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

Simulating the mechanisms of serrated flow in interstitial alloys with atomic resolution over diffusive timescales

Abstract The Portevin-Le Chatelier (PLC) effect is a phenomenon by which plastic slip in metallic materials becomes unstable, resulting in jerky flow and the onset of inhomogeneous deformation. The PLC effect is thought to be fundamentally caused by the dynamic interplay between dislocations and solute atoms. However, this interplay is almost always inaccessible experimentally due to the extremely fine length and time scales over which it occurs. In this paper, simulations of jerky flow in W-O interstitial solid solutions reveal three dynamic regimes emerging from the simulated strain rate-temperature space: one resembling standard solid solution strengthening, another one mimicking solute cloud formation, and a third one where dislocation/solute coevolution leads to jerky flow as a precursor of dynamic strain aging. The simulations are carried out in a stochastic framework that naturally captures rare events in a rigorous manner, providing atomistic resolution over diffusive time scales using no adjustable parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A multivariate library of zirconia metal–organic frameworks with dissolved p -nitroaniline dipoles and concentration-dependent optical and dielectric response

In this work, we show how the combination of soluble non-polar and polar links allows for the preparation of multivariate metal–organic frameworks (MTV MOFs) that exhibit dipolar solid-solution behavior. We prepared a library of PIZOF-2 MOFs with varied concentrations of p -nitroaniline (PNA)-containing moiety embedded within the MTV links. This library forms a partial solid solution up to 30 mol% with input/output composition ratio of 0.536 ± 0.018. MOFs with x > 5 mol% PNA show concentration-dependent hypsochromic dipole–dipole coupling (H-coupling) in the solid-state UV-visible spectra. The MTV library also exhibits a dielectric relaxation event in the broadband dielectric spectra with activation enthalpies and entropies that vary with temperature and PNA content and follow linear Meyer–Neldel compensation relations.

Langlois, Kyle R. [Univ. of Central Florida, Orlan↗
NASA NTRS1972

Study of X-ray diffraction on aging alloys with different degrees of volume discrepancy between the precipitation phase and the matrix

Study of the diffraction patterns of X rays diffracted by dispersion-hardened alloys with various degrees of difference between the specific atomic volumes of their precipitation phases and matrices. Experiments were performed on aging alloys KhN77TIuR (nimonic) and KhN67VMTIuO, which have the same types of gamma solid solutions and precipitating gamma prime phases, but differ considerably with respect to the volume factor. It is found that in the decay of supersaturated solid solutions for which the difference between the specific atomic volumes of the precipitation phase and the matrix is small (alloy KhN67VMTIuO) the nature of the intensity distribution of the diffraction lines remains practically unchanged regardless of the aging, while in cases where the volume discrepancy is large (alloy KhN77TIuR) significant changes in the appearance of the diffraction lines are recorded.-

Gitgarts, M. I.↗
DOE OSTI2025

Analcime-wairakite formation during experimental cement-bentonite alteration at 200–300 °C

Engineered barrier system materials in nuclear waste repositories may undergo hydrothermal alteration in response to groundwater saturation and heating events over their long operational timescales. Hydrothermal interactions between engineered materials (e.g., bentonite buffers, cements, waste canister materials) and the host rock environment may drive alteration processes that affect the advantageous properties of some barrier materials. However, such alteration will also promote the formation of zeolites, hydrothermally formed minerals that may themselves act to isolate radionuclides. Understanding the environmental conditions that control radionuclide-sorbing properties of zeolites, such as Si/Al ratio or Na content, will be valuable for assessing the changing properties of engineered barrier materials in the case of an in situ heating event. Here, we present experimental work characterizing the formation of zeolites during hydrothermal interactions between generic clay and cement barrier materials, with a focus on the analcime-wairakite zeolite series, which has known radionuclide sorption and exchange properties. We present the results of hydrothermal experiments combining uncured ordinary Portland cement powder with steel and Wyoming bentonite in the presence of Opalinus clay and a synthesized Opalinus clay groundwater to simulate water-saturated conditions in an argillaceous rock repository. The experiments were conducted isothermally at 200 or 300 °C for 8 to 24 weeks. In contrast to analogous studies that did not include cement reactants, we observed the formation of analcime-group minerals in all experiments. The addition of cement resulted in lower Si/Al ratios in the zeolites compared to similar studies that did not include cement. The presence of cement as a reactant was interpreted to promote analcime formation at 200 °C. At 300 °C, we observed higher calcium and silica concentrations in the aqueous solutions as well as increased wairakite formation and decreased analcime formation compared to the experiments at 200 °C. These results show a fully realized analcime-wairakite solid solution that falls between Si/Al = 2 (ideal) and a trend of analcime minerals that have increasing Si/Al ratios with increasing Na/(Na+Ca). Our results show predictable relationships between the Si/Al ratio and the analcime-wairakite content under hydrothermal conditions and illustrate that repository material interactions may promote the formation of zeolites in the analcime-wairakite solid-solution series during heating events in the subsurface.

58 GEOSCIENCES↗
DOE OSTI2022

Defect control in the Heisenberg-Kitaev candidate material NaRuO 2

The combination of geometric frustration, extended hopping, spin-orbit coupling, and a disordered magnetic ground state make NaRuO 2 an attractive Heisenberg-Kitaev candidate material. Historically, NaRuO 2 has been a challenging material to produce, even in polycrystalline form. Here we present synthetic efforts that identify a propensity for Na Ru defects to form in NaRuO 2 , revealing a full solid-solution between NaRuO 2 and disordered Na 2 RuO 3 . We report the synthesis of alloys along the Na 3+x Ru 3–x O 6 solid solution and characterize changes in the bulk magnetization and electron transport as a function of Na loading. Furthermore, our results highlight the importance of stoichiometry control in NaRuO 2 when investigating and interpreting this material’s physical properties.

36 MATERIALS SCIENCE↗