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All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

First-principles thermodynamic assessment of Sr-containing secondary phase formation in strontium-substituted lanthanum manganites for solid oxide cell applications

Sr-secondary phase formation is a potentially significant degradation mode with direct impact upon solid-oxide cell (SOC) commercial viability. A first-principles based thermodynamic study was performed for La 1−x Sr x MnO 3±δ (LSM) perovskites to assess their stability against formation of different Sr-secondary phases, including SrO, SrCrO 4 , SrSO 4 , SrCO 3 , and Sr(OH) 2 , for SOC applications. The Sr-secondary phase formation reaction free energies were determined via a thermodynamic model by combining ab initio lattice dynamics calculations for the solid phases and ab initio thermodynamic data for the gas phases. The current approach expands the previously reported thermodynamic modeling studies by integrating first-principles based point defect equilibria into the thermodynamic analysis. The modeling results obtained using this new approach indicate an increased tendency to form the SrO oxide upon decreasing the oxygen partial pressure. Additionally, the enhancing factors to form the Sr-related secondary phase from the associated SrO activity in LSM are further quantified by considering the equilibrium of SrO reacting with the contaminant gas species as a function of temperature and pressure.

defect thermodynamics modeling↗
DOE OSTI2024

Stability of the first-order character of phase transition in HoCo 2

HoCo 2 exhibits a giant magnetocaloric (MC) effect at its first-order magnetostructural phase transition around 77 K, and understanding the thermodynamic nature of this transition in response to external magnetic fields is crucial for its MC applications. In this study, we present a comprehensive investigation of specific heat and magnetization measurements of HoCo 2 under varying magnetic fields. The specific heat measurements qualitatively indicate a transformation from first- to second-order behavior of this phase transition at higher magnetic fields. However, analysis of the power-law dependence of the magnetic entropy change (Δ S M ∝H n ) and the breakdown of universal behavior in the temperature dependence of Δ S M suggest that the first-order nature remains intact, even up to 7 T. This stability of the first-order nature is further manifested through the distinctive non-linear behavior of modified Arrott plots, with a negative slope in the 6–7 T range.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Solar Steam on Demand

INTRODUCTION: This Report summarizes the research and development project performed by Sunvapor and the subrecipient National Renewable Energy Laboratory (NREL) during the period of 10/01/2018-9/30/2021. The work was aimed at the economic integration of solar steam with an industrial process, and in particular, the advantages that a novel type of thermal energy storage and collector design could bring to the system. The completed work includes experimental research on the storage material, design of the collector, engineering of a complete solar steam plant, and economic analysis. The plant was, in the end, not constructed, due to COVID-19 impacts to the project host. PURPOSE: The purpose of the project was to test the hypothesis that a levelized cost of heat (LCOH) of 2¢/kWh delivered to a steam-consuming process, including energy discharged from storage, could be feasibly achieved. PROJECT OBJECTIVES: For Budget Period 1 our objectives were to engineer a prototype industrial solar steam generation system, and design and test a Latent Heat Energy Storage (LHES) lab-scale system. For Budget Period 2 our objectives were to construct and test the solar steam prototype plant, and to build and factory-test a full LHES module. For Budget Period 3 our objective was to integrate the storage module with the solar steam generator, show successful long duration energy tests of the combined system, and use the results to project the LCOH of delivered steam to a second-generation plant. PROJECT OUTCOMES: Various phase change materials (PCMs) for the LHES were tested for compatibility with industrial steam uses as measured by phase change temperature, stability of latent heat of fusion, and their corrosive effects on steel (the heat exchanger material). Two of these materials (sodium formate and sodium/ potassium) showed potential to meet the technical criteria. The estimated cost of a complete LHES module with these materials did not meet economic targets. The developmental collector design builds from previous work to exploit the potential cost advantages of a spaceframe of lumber construction. Design improvements were achieved in assembly efficiency and structural performance. A complete engineering package was completed for the solar steam system without storage that included the developmental as well as commercial arrays. The plant was permitted for construction. The storage CAPEX for a reference plant was estimate to be greater than $\$ 57$/kWh. The LCOH of the system without storage and with developmental collectors of lumber construction was projected to be 2¢/kWh, assuming a FCR of 8.2% over thirty years. PROJECT MILESTONES: The Milestones fully achieved in the first Budget Period includes obtaining a Letter of Intent from an industrial steam-consuming project host, issuance of a construction permit, and corrosion resistance. The Milestone that was partly achieved was the degradation in the latent heat of fusion. Milestones associated with Budget Periods 2 and 3, related to the construction and operation of the plant were not achieved as a result of the host shutting down the plant due to COVID-19 impacts. CONCLUSIONS: Sunvapor was able to secure an agreement with a host to build a fully engineered and permitted solar steam plant that met the host’s economic goals. As a basis for comparison, the solar field design was comprised of eight commercial collector arrays and one developmental Green Parabolic Trough Collector (GPTC) array. The projected LCOH with a solar field entirely populated with a second generation GPTC met the goal of 2¢/kWh. The experimental program concerning the PCM indicated the feasibility of meeting their technical requirements for industrial steam uses. The cost of the complete LHES exceeded its $\$ 14$/kWh target, and therefore the inclusion of LHES could not be economically justified. Due to COVID-19 impacts on the host, the solar steam plant was not constructed.

14 SOLAR ENERGY↗
DOE OSTI2022

Synthesis and structure of high-purity BaCe 0.25 Mn 0.75 O 3 : an improved material for thermochemical water splitting

Solar thermochemical hydrogen production (STCH) via redox-active metal oxides is an approach for direct solar-driven hydrogen generation typically using a high-temperature redox cycle involving refractory oxides and steam. Typical cycles involve high-temperature reduction of oxides to form oxygen vacancies, followed by lower temperature reaction between oxygen vacancies and steam where the oxide is re-oxidized and the steam is reduced to hydrogen. Only a few materials have demonstrated reversible cycling under the typically harsh STCH conditions (e.g. 1500°C reduction, 900°C re-oxidation) and critical questions remain on the true reversibility of non-stoichiometric multi-cation oxide systems, significantly hampered by the lack of single-phase samples for these material systems. To date, most STCH processes have relied on CeO 2 as a benchmark active material, but more recently, the 12R phase of BaCe 0.25 Mn 0.75 O 3 (BCM) has demonstrated greater hydrogen-generation potential at lower peak temperatures. However, previous reports of 12R-BCM have included large fractions, > 10 wt%, of secondary phases, which complicate analysis of the stability and performance. A comprehensive understanding of the redox mechanism and reversibility of the process in BCM can only be achieved with nearly single-phase samples which, to date, have been difficult to produce. Here two approaches to BCM synthesis are reported: solid state and sol–gel-based routes. It is demonstrated that both routes can be tuned to produce the 12R structure with > 97 wt% yield when annealed ≥1450°C. Herein synchrotron-based diffraction measurements of rhombohedral 12R-BCM enabled characterization of the anisotropy between thermal expansion along the c-axis and within the ab plane. The impact of high-temperature redox cycling on the stability and phase fraction of the 12R-BCM polytype was also investigated. Our results offer two viable routes for synthesis of high-purity 12R-BCM critically needed for evaluating the efficacy of BCM as a STCH material and validate its ability to split water at lower temperatures over extended numbers of redox cycles.

08 HYDROGEN↗
DOE OSTI2025

Tailoring P2/P3‐Intergrowth in Manganese‐Based Layered Transition Metal Oxide Positive Electrodes via Sodium Content for Na‐Ion Batteries

High-manganese content sodium-ion positive electrodes have received heightened interest as an alternative to contemporary Li-ion chemistries due to their high abundance, low toxicity, and even geographical distribution. However, these materials typically suffer from poor capacity, unstable cycling performance, and sluggish Na + kinetics. Herein, we explore a manganese-based layered transition metal oxide (Na x N 0.25 Mn 0.75 O 2 ) and show by X-ray diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that careful variation of the sodium content can instigate the formation of a biphasic intergrowth. This intergrown P2/P3 material offered a higher capacity than its monophasic P2 counterpart due to the P3 structure having greater low-voltage Mn 3+/4+ redox. Further, the intergrowth material offers greatly enhanced kinetics and cycling stability when compared to single-phase P3 material, due to the stabilizing nature of the P2 structure, elucidated by galvanostatic intermittent titration technique (GITT) and operando synchrotron X-ray diffraction. These results highlight the beneficial effect that the intergrowth structure has on the electrochemical performance of high-manganese content positive electrode for future sodium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

Intermediate temperature solid oxide fuel cells (IT-SOFCs) are cost-effective and efficient energy conversion systems. Here, the sluggish oxygen reduction reaction (ORR) and the degradation of cathodes are critical challenges to the commercialization of IT-SOFCs. Here, a highly efficient multiphase (MP) catalyst coating, consisting of Ba 1–x Co 0.7 Fe 0.2 Nb 0.1 O 3–δ (BCFN) and BaCO 3 , to enhance the ORR activity and durability of the state-of-the-art lanthanum strontium cobalt ferrite (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ , LSCF) cathode is reported. The conformal MP catalyst-coated LSCF cathode shows a polarization resistance (R p ) of 0.048 Ω cm 2 at 650 °C, about one order of magnitude smaller than that of the bare LSCF. In an accelerated Cr-poisoning test, the degradation rate of the catalyst-coated LSCF electrode is 10 –3 Ω cm 2 h –1 (0.59% h –1 ) over 200 h, only one fifth of the degradation rate of the bare LSCF electrode at 750 °C. In addition, anode-supported single cells with the MP catalyst-coated LSCF cathode show a dramatically enhanced peak power density (1.4 W cm –2 vs 0.67 W cm –2 at 750 °C) and increased durability against Cr and H 2 O. Both experimental results and density functional theory-based calculations indicate that the BCFN phase improves the ORR activity while the BaCO 3 phase enhances the stability of the LSCF cathode.

solid oxide fuel cells↗
DOE OSTI2025

Effect of Propagating Dopant Reactivity on Lattice Oxygen Loss in LLZO Solid Electrolyte Contacted with Lithium Metal

Lithium lanthanum zirconium oxide (LLZO) is widely known as the most stable solid electrolyte against lithium metal electrodes. This thermodynamic stability can be lost by the presence of dopants which are required to stabilize the cubic phase of LLZO and can be reduced by lithium metal. However, the role of oxygen in such reactions is taken for granted. In this work, the reduction of Nb-substituted LLZO (Nb-LLZO) is explored by Li metal and shows that interfacial reactions propagate and lead to the decomposition with substantial Nb 5+ reduction deep into the bulk electrolyte. Scanning Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy and thermogravimetric analyses show much of the reduction is due to oxygen vacancies formed, leading to increased electronic conductivity mapped with conductive Atomic Force Microscopy. Density functional theory calculations indicate oxygen release is favored by increased excess lithiation of Nb-LLZO. Electrochemical impedance of polycrystalline Nb-LLZO shows the continuous evolution of ionically resistive interphases near the lithium metal interface with Nb-LLZO while single crystals show little reactivity at room temperature and self-limiting reduction at 60°C. This work underlines the role of grain boundaries in propagating destructive solid electrolyte reactions and highlights previously unseen mechanisms involving lattice oxygen in LLZO.

Li metal, solid-state electrolytes↗
DOE OSTI2020

A Pressure‐Induced Inverse Order–Disorder Transition in Double Perovskites

Abstract Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure‐induced disordering could require recognition of an order–disorder transition in solid‐state physics/chemistry and geophysics. Double perovskites Y 2 CoIrO 6 and Y 2 CoRuO 6 polymorphs synthesized at 0, 6, and 15 GPa show B‐site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long‐range ferrimagnetic ordering in the B‐site ordered samples are gradually overwhelmed by B‐site disorder. Theoretical calculations suggest that unusual unit‐cell compressions under external pressures unexpectedly stabilize the disordered phases of Y 2 CoIrO 6 and Y 2 CoRuO 6 .

Deng, Zheng↗
DOE OSTI2025

Photocatalytic Activity and Stability of Carbon Nitride‐Pyrite Composites

Abstract In photocatalysis, the photoabsorber plays a crucial role in the reaction. The most important parameters are stability, cost and optical band gap. In this work, a prominent class of absorbers, namely carbon nitrides (CN), has been investigated. In the literature, CN is most often described as stable, although photodegradation has been observed. In order to retain the beneficial properties of CN while improving stability, a crystalline phase poly(triazine imide) (PTI) of carbon nitride was investigated and compared to polymeric CN in photocatalytic hydrogen generation experiments. In order to improve the charge separation for the photoinduced hydrogen evolution reaction, pyrite (FeS 2 ) was used as a surface co‐catalyst with a loading of 1, 5 and 10 wt %. At the same time, any photodegradation products in solution were investigated by ion chromatography. Interestingly, PTI shows hardly any photocorrosion compared to defective carbon nitride, indicating its higher photostability in hydrogen evolution experiments. However, FeS 2 produces ammonium as a degradation product when synthesised from nitrogen‐containing precursors. When made from nitrogen‐free precursors, FeS 2 together with photostable PTI releases little ammonia, making it a photostable, earth‐abundant composite for photocatalytic hydrogen generation.

Kaulbersch, Julian [University of Bayreuth 95440 B↗
DOE OSTI2022

Structure and thermodynamics of calcium rare earth silicate oxyapatites, Ca 2 RE 8 (SiO 4 ) 6 O 2 (RE = Pr, Tb, Ho, Tm)

Calcium rare earth silicate oxyapatites, (Ca 2 RE 8 (SiO 4 ) 6 O 2 ), are of interest as components of glass-ceramic nuclear waste forms. To assess their long-term behavior in a geologic repository, it is essential to determine their structure and thermodynamic stability at relevant conditions. Here, in this work, we performed detailed structural and thermodynamic investigations on Ca 2 Pr 8 (SiO 4 ) 6 O 2 , Ca 2 Tb 8 (SiO 4 ) 6 O 2 , Ca 2 Ho 8 (SiO 4 ) 6 O 2 , and Ca 2 Tm 8 (SiO 4 ) 6 O 2 by high energy synchrotron powder X-ray diffraction combined with Rietveld analysis and high temperature oxide melt drop solution calorimetry. Enthalpies of formation from constituent oxides (ΔH f,ox ) were determined to be -765.1 ± 22.8 kJ/mol for Ca 2 Pr 8 (SiO 4 ) 6 O 2 ; -638.9 ± 20.5 kJ/mol for Ca 2 Tb 8 (SiO 4 ) 6 O 2 ; -643.3 ± 10.3 kJ/mol for Ca 2 Ho 8 (SiO 4 ) 6 O 2 ; and -403.2 ± 5.1 kJ/mol for Ca 2 Tm 8 (SiO 4 ) 6 O 2 . These thermodynamic parameters were used in assessing the thermochemical stability of these phases in the presence of water vapor from room temperature to 600 K, as encountered in the subsurface environments of a geological repository.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A General Model for the Ductility of Intermetallics Applied to Fe-Co Alloys

The mechanical properties, specifically ductility, of high performing soft magnets such as Fe-Co alloys are a limiting factor to their broader use in a number of systems. The understanding of the mechanical robustness in these materials is currently insufficient to be able to support the growing interest in applications such as magnetic shielding or electric motors. Fe-Co alloys provide the highest commercially available magnetic saturation and high magnetic permeability but have very poor ductility. The addition of vanadium to these alloys has allowed for significant commercialization and some ductility improvements, but the fundamental reasons for the observed improvements are not well understood. In most published work on mechanical properties in these alloys, the precise chemistry of the alloys investigated, often a critical aspect of intermetallics, is not reported or controlled and thermal history is unclear. This work creates a ductility model that is sensitive to changes in chemistry and can predict relative strain to failure as well as brittle fracture mode for intermetallics and is applied to Fe-Co alloys. Through the application of density functional theory (DFT), this model identifies defect stabilities, anti-phase boundary (APB) energies, the energy necessary to cross-slip, and cleavage energies and combines them through energetic competition to determine a relative failure strain. The model correctly predicts ductility improvements with the addition of vanadium as well as the transition from intergranular to transgranular cleavage, though more precise experiments are necessary to appropriately validate the various improvements observed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Flame aerosol synthesis of hollow alumina nanoshells for application in thermal insulation

Commercial implementation of hollow nanoshell materials is often limited by difficult scale-up and high cost. Here we present a scalable, continuous, and potentially low-cost route to hollow nanostructured materials using a High Temperature Reducing Jet flame aerosol reactor. The key advantage of this process over traditional flame aerosol synthesis methods is separation of flame chemistry and particle formation, which allows production of hollow nanoshells from an aqueous salt solution without any template or surfactant. We produced amorphous hollow alumina with an average diameter of 181 nm and shell thickness below 10 nm, and demonstrated the generality of the method by also producing hollow SiO 2 , ZrO 2 , Ga 2 O 3 , and Co 2 O 3 . We characterized the morphology, phase transition, thermal stability, and thermal conductivity of the flame-made hollow alumina by electron microscopy, x-ray diffraction, and thermal analysis methods. As a prototypical application, we incorporated hollow alumina into thermal insulation, combining it with common fiberglass insulation to reduce the thermal conductivity by 30% relative to pure fiberglass, to 0.028 W m -1 K -1 while maintaining robust fire-resistance and elasticity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Atomically precise synthesis of oxides with hybrid molecular beam epitaxy

Advancements in synthesis science are revolutionizing the way we create atomically precise materials. Techniques like molecular beam epitaxy (MBE) have set the benchmark for addressing long-standing questions in materials science by leveraging improved control over the composition and structure of existing materials and enabling materials discovery. In this review, we discuss recent innovations in MBE that are redefining its capabilities, enabling the fabrication of ultra-pure, defect-engineered films and the stabilization of metastable phases that were previously unattainable. These advancements are unlocking new opportunities in electronic, magnetic, and quantum technologies, where the precise tuning of material properties is essential for advancing device functionality and performance.

complex oxides↗
DOE OSTI2026

Unraveling the Synergistic effects of La and Al co-doping on Ni/Co-free P2-type Na 0.67 Mn 0.67 Fe 0.33 O 2 layered oxide cathodes for sodium-ion batteries

Recent developments in high-performance cathodes for sodium-ion batteries (SIBs) tend to mitigate use of critical Ni and Co active species to satisfy sustainability. P2-type layered oxide cathodes based on Mn and Fe promise high capacity, sustainability, and low cost on account of the abundance and multiple redox characteristics of Mn and Fe. However, their commercialization is still challenged due to poor cycling stability caused by phase changes emanating from inherent Jahn-Teller distortions. Herein, we propose a novel strategy of trivalent La and Al co-doping to alleviate the drawbacks, innovating a new cathode of Na 0.67 Mn 0.62 Al 0.05 Fe 0.31 La 0.02 O 2 (AlLa). The co-doped cathode delivers an impressive capacity of 128.7 mAh/g at 1C and 106.5 mAh/g at high rate of 5C with a good capacity retention of 85% after 100 cycles. These are superior to the unmodified material, whose specific capacity was 118.6 mAh/g at 1C and 61.1 mAh/g at 5C with a retention of only 65% after 100 cycles. The synergistic contribution from La and Al associated with their improved oxygen bonding, pillaring, and local electronic structural modification stemming from rigid Lasingle bondO and Alsingle bondO bonding resulted in the observed structural and electrochemical improvement. Overall, this research offers novel strategies for designing high-performance cathode materials for sodium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Energetics of hydroxylbastnäsite solid solutions, La 1-$\chi$ Nd $\chi$ CO 3 OH

Bastnäsites (LnCO 3 (F,OH)) are a group of common rare earth elements (REE)-bearing minerals and are one of the primary global sources of REE. Due to the chemical similarities among REE, bastnӓsites tend to occur as solid solutions instead of end members in REE containing ores. To better understand the processes and the mechanisms of formation of such deposits, it is essential to determine the thermodynamic properties of bastnӓsites, including hydroxylbastnӓsite (LnCO 3 OH) solid solutions. In this work, we performed detailed structural and calorimetric investigations on synthetic hexagonal La–Nd hydroxylbastnӓsite (La 1-$\chi$ NdCO 3 OH, $\chi$ = 0, 0.25, 0.5, 0.75, 1) solid solutions. X-ray diffraction confirms the crystal structure of the solid solution series in the $\ P$6 space group, and pair distribution function (PDF) analysis reveals local bonding environments characterized by three different types of 9-coordinated metal-oxygen polyhedra. Unit cell parameters of La1–xNdxCO3OH exhibit a nearly linear relation with the Nd content x, suggesting a random distribution of La and Nd in the structure. Their standard enthalpies of formation (Δ$\ H$° f ) were determined by high temperature oxide melt drop solution calorimetry, from which the enthalpies of mixing (Δ$\ H$ mix ) were derived. The Δ$\ H$ mix can be fitted by a regular solution model with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting enthalpic metastability of La1–xNdxCO3OH relative to the two endmembers. Combining entropy and enthalpy, we further estimated the Gibbs free energies of mixing (Δ$\ G$ mix ) at relevant temperatures, revealing favorable temperatures under which the intermediate La 1-$\chi$ NdCO 3 OH phases can be stabilized. Such entropy-driven stabilization, as is consistent with our geochemical modeling results, may explain the enhancement of thermal stability of the solid solutions in nature. Additionally, the temperature range constrained from this study may be used to estimate the thermal history of REE bastnӓsite deposit.

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

Sluggish atomic dynamics in a Y-Sc-Co-Al high entropy bulk metallic glass

We present how 20 at% Sc addition affects the atomic packing and dynamics in a Y-Co-Al metallic glass (MG) and find that it greatly suppresses the dynamics of Co atoms by reducing the atomic packing difference in their surroundings. The Co atoms tending to be mobile or static depend on their nearest neighbors, i.e., possessing more Y/Y+Sc atoms but fewer Co atoms or vice versa. The X-ray absorption fine structure results confirm that Sc addition mainly changes the local environment around Co atoms, forming more Co-Co and Co-Sc pairs but significantly fewer Co-Y pairs than in the ternary counterpart, which can seriously slow the atomic dynamics and stabilize the competing phases. Our findings shed new light on the understanding of strong glass forming ability of the Sc-added Y-based high entropy MG from its local structure and dynamics and will be helpful in developing new bulk MGs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A linearity preserving nodal variation limiting algorithm for continuous Galerkin discretization of ideal MHD equations

A stabilized continuous Galerkin (CG) method for magnetohydrodynamics (MHD) is presented herein. Ideal, compressible inviscid MHD equations are discretized in space on unstructured meshes using piecewise linear or bilinear finite element bases to get a semi-discrete scheme. Stabilization is then introduced to the semi-discrete method in a strategy that follows the algebraic flux correction paradigm. This involves adding some artificial diffusion to the high order, semi-discrete method and mass lumping in the time derivative term. The result is a low order method that provides local extremum diminishing properties for hyperbolic systems. The difference between the low order method and the high order method is scaled element-wise using a limiter and added to the low order scheme. The limiter is solution dependent and computed via an iterative linearity preserving nodal variation limiting strategy. The stabilization also involves an optional consistent background high order dissipation that reduces phase errors. The resulting stabilized scheme is a semi-discrete method that can be applied to inviscid shock MHD problems and may be even extended to resistive and viscous MHD problems. To satisfy the divergence free constraint of the MHD equations, we add parabolic divergence cleaning to the system. Various time integration methods can be used to discretize the scheme in time. We demonstrate the robustness of the scheme by solving several shock MHD problems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗