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DOE OSTI2020

Materials Data on Sr(NiP2)2 by Materials Project

Sr(NiP2)2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Sr2+ is bonded to eight equivalent P1- atoms to form distorted SrP8 hexagonal bipyramids that share corners with sixteen equivalent NiP4 tetrahedra and edges with four equivalent SrP8 hexagonal bipyramids. There are four shorter (3.12 Å) and four longer (3.14 Å) Sr–P bond lengths. Ni1+ is bonded to four equivalent P1- atoms to form NiP4 tetrahedra that share corners with eight equivalent SrP8 hexagonal bipyramids and edges with two equivalent NiP4 tetrahedra. There are two shorter (2.21 Å) and two longer (2.22 Å) Ni–P bond lengths. P1- is bonded in a 6-coordinate geometry to two equivalent Sr2+, two equivalent Ni1+, and two equivalent P1- atoms. There are one shorter (2.23 Å) and one longer (2.25 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr(SbRu)2 by Materials Project

Sr(RuSb)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr2+ is bonded in a body-centered cubic geometry to eight equivalent Sb3- atoms. All Sr–Sb bond lengths are 3.54 Å. Ru2+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing RuSb4 tetrahedra. All Ru–Sb bond lengths are 2.60 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Sr2+, four equivalent Ru2+, and one Sb3- atom. The Sb–Sb bond length is 3.12 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr(RuO3)2 by Materials Project

Sr(RuO3)2 is Hydrophilite-derived structured and crystallizes in the trigonal P-31m space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent O2- atoms to form SrO6 octahedra that share corners with twelve equivalent RuO6 octahedra. The corner-sharing octahedral tilt angles are 54°. All Sr–O bond lengths are 2.57 Å. Ru5+ is bonded to six equivalent O2- atoms to form RuO6 octahedra that share corners with six equivalent SrO6 octahedra and edges with three equivalent RuO6 octahedra. The corner-sharing octahedral tilt angles are 54°. All Ru–O bond lengths are 1.96 Å. O2- is bonded in a distorted trigonal planar geometry to one Sr2+ and two equivalent Ru5+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr(HoS2)2 by Materials Project

Sr(HoS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Sr–S bond distances ranging from 3.09–3.29 Å. There are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six S2- atoms to form a mixture of edge and corner-sharing HoS6 octahedra. The corner-sharing octahedra tilt angles range from 48–63°. There are a spread of Ho–S bond distances ranging from 2.70–2.76 Å. In the second Ho3+ site, Ho3+ is bonded to six S2- atoms to form a mixture of edge and corner-sharing HoS6 octahedra. The corner-sharing octahedra tilt angles range from 48–63°. There are a spread of Ho–S bond distances ranging from 2.68–2.76 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Sr2+ and three Ho3+ atoms. In the second S2- site, S2- is bonded to two equivalent Sr2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing SSr2Ho3 square pyramids. In the third S2- site, S2- is bonded to two equivalent Sr2+ and three Ho3+ atoms to form a mixture of distorted edge and corner-sharing SSr2Ho3 trigonal bipyramids. In the fourth S2- site, S2- is bonded to two equivalent Sr2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing SSr2Ho3 trigonal bipyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Am-241, Pu-238, Pu-239/240, and Sr-90 Decision Levels for the Environmental Air Monitoring Program for the Idaho National Laboratory

This report provides a comprehensive analysis of Am-241, Pu-238, Pu-239/240, and Sr-90 radiation data collected from air monitoring sites at or near Idaho National Laboratory from June 2013 through December 2020. These data were used to compute monitoring limits that will be used to assess future measurements of Am-241, Pu-238, Pu-239/240, and Sr-90. Data were analyzed for seasonality, stationarity, and other data issues that may impact the calculation and use of the monitoring limits.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Sr and Co Vapor-Phase Transport from LSCF Cathodes

A series of tests were performed to differentiate between surface diffusion and vapor-phase diffusion of chemical species from LSCF cathode material at typical sintering temperatures (up to 1100°C) in SOFC production. A GDC source substrate was printed with LSCF and separated by an air gap from a YSZ target substrate. Various geometries with long surface paths were employed to reduce the possibility of surface transport. Sr and Co were detected on the target substrates via energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS), including spatially resolved XPS. These results support a vapor-phase transport mechanism for Sr and Co. Sintering conditions and barrier layer requirements may need to be revisited to prevent the formation of undesired strontium zirconate at cathode/electrolyte interface due to vapor-phase transport.

vapor phase transport, SOFC cathode, Sr transport↗

DOE OSTI2023

Resolving Diverse Oxygen Transport Pathways Across Sr‐Doped Lanthanum Ferrite and Metal‐Perovskite Heterostructures

Abstract Perovskite structured transition metal oxides are important technological materials for catalysis and solid oxide fuel cell applications. Their functionality often depends on oxygen diffusivity and mobility through complex oxide heterostructures, which can be significantly impacted by structural and chemical modifications, such as doping. Further, when utilized within electrochemical cells, interfacial reactions with other components (e.g., Ni‐ and Cr‐based alloy electrodes and interconnects) can influence the perovskite's reactivity and ion transport, leading to complex dependencies that are difficult to control in real‐world environments. Here, this work uses isotopic tracers and atom probe tomography to directly visualize oxygen diffusion and transport pathways across perovskite and metal‐perovskite heterostructures, that is, (Ni‐Cr coated) Sr‐doped lanthanum ferrite (La 0.5 Sr 0.5 FeO 3 ; LSFO). Annealing in 18 O 2(g) results in elemental and isotopic redistributions through oxygen exchange (OE) in the LSFO while Ni‐Cr undergoes oxidation via multiple mechanisms and transport pathways. Complementary density functional theory calculations at experimental conditions provide rationale for OE reaction mechanisms and reveal a complex interplay of different thermodynamic and kinetic drivers. These results shed light on the fundamental coupling of defects and oxygen transport in an important class of catalytic materials.

36 MATERIALS SCIENCE↗

DOE OSTI2022

(La 0.8 Sr 0.2 ) 0.98 MnO 3-δ -Zr 0.92 Y 0.16 O 2-δ :PrOx for oxygen electrode supported solid oxide cells

(La 0.8 Sr 0.2 ) 0.98 MnO 3-δ (LSM)- Zr 0.92 Y 0.16 O 2-δ (YSZ) has been widely studied as the cathode for solid oxide fuel cells (SOFCs), but its low activity has been a cell performance limiting factor. Herein, LSM-YSZ:PrO x composite is developed as an active electrocatalyst for both oxygen reduction and evolution reactions. A single step PrO x infiltration into LSM-YSZ lowers the polarization resistance (Rp) 10–20 times depending on the test temperature. Distribution of relaxation times (DRT) calculation reveals that adding PrO x affects surface exchange between adsorbed/desorbed oxygen and lattice oxygen, and oxygen dissociative adsorption/desorption. A symmetrical cell with a thin YSZ electrolyte sandwiched between thick LSM-YSZ:PrO x electrode-supports is developed and its oxygen generation performance and stability are evaluated under various current densities and temperatures. Finally, reversible solid oxide cell (ReSOC) performance is also reported for LSM-YSZ:PrO x supported cells with the oxide fuel electrode Sr 0.95 (Ti 0.3 Fe 0.63 Ni 0.07 )O 3-δ (STFN).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Nickel B-site substitution in bulk Sr 1-x Ca x FeO 3 perovskite oxygen carriers: Benefits and limitations

We report oxygen (O 2 ) storage materials often rely on the presence of cobalt (Co) to reduce the thermodynamic penalty and increase the kinetics necessary for efficient O 2 storage and release. In this work, we investigate nickel (Ni) as an alternative B-site dopant in Sr 1-x Ca x FeO 3 to identify Co-free carriers that still show improved kinetics at low temperatures. In fact, we show a substantial increase in the reversible O2 release rate through mild Ni B-site substitution (y = 0.06) in select Sr 1-x Ca x Fe 1-y Ni y O 3 systems at 400 to 500 °C, reaching 2.00 wt.% O 2 release up to approximately 75% faster than Ni-free systems. To explain the role of Ni in these systems, we use density functional theory to calculate the O 2 vacancy (V O ) formation energy from separate metal-oxygen (M-O) bonding and relaxation components. We computationally show elongated Ni-O bonds are directly responsible for the decrease in V O upon Ni substitution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Catalyzed oxidation of nuclear graphite by simulated fission products Sr, Eu, and I

The influence of three fission products Sr, Eu, and I on the oxidation of IG-110 nuclear graphite was studied in the temperature range of 400 to 1000 °C. Sr and Eu were introduced as chlorides, and I was introduced as NaI. The temperature dependence of both CO 2 and CO production during the graphite oxidation measured with mass spectroscopy and infrared spectrometry shows that the introduction of these three compounds to graphite significantly decreases the onset temperature for the oxidation of graphite. Among the three compounds, NaI is the most active towards the oxidation reaction, characterized by a significant decrease of the onset temperature from approximately 650 to 400 °C before and after its introduction to graphite. Separate measurements of CO 2 and CO concentration at varying temperatures enable the calculation of the activation energy for the formation of CO 2 and CO. The activation energies for the oxidation of pure and fission product-impregnated graphite samples decrease in the following order: standard IG-110 graphite, EuCl 3 -impregnated IG-110, SrCl 2 -impregnated IG-110, and NaI-impregnated IG-110. This trend indicates that the three compounds catalyze the oxidation of graphite at temperatures relevant to the operation of high-temperature gas-cooled reactors. Furthermore, it is found that the three compounds can also affect the molar ratio of reaction products CO 2 and CO, and the rates of the graphite oxidation. At temperatures higher than about 850 °C, the impregnated samples exhibit lower CO 2 : CO ratios than the pure graphite. Different from EuCl 3 and NaI, the introduction of SrCl 2 decreases the graphite oxidation rates at temperatures higher than about 770 °C. Their catalytic mechanism can be understood based on a redox cycle of the intermediate active species, promoting the dissociation of molecular oxygen and transfer to the carbon.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2020

The effect of water vapor on surface oxygen exchange kinetics of thin film (La,Sr)(Co,Fe)O 3-δ

Oxygen reduction and transport in electrochemical applications are strongly affected by the reactant gas composition, including impurities such as water. Understanding the relationship between oxygen reactivity and humidity is key for attaining stability and high efficiency of solid oxide fuel cells, which are especially attractive for transportation applications as low emission power generation devices. Both short- and long-term effects of moisture have previously been associated with use of ambient air. To better understand these effects, we study oxygen exchange kinetics at the cathode surface and the cathode/electrolyte interface using La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) epitaxial thin films as a model-surface system. In situ synchrotron X-ray techniques evaluate the oxygen reduction reaction (ORR) kinetics in response to environmental variables. The results suggest a clear enhancement of the ORR rate upon short term exposure of the perovskite-structured films to water. Finally, on the basis of these measurements, along with in situ X-ray characterization of Sr segregation and computational first-principles studies, we suggest a model for this increased ORR activity that may lead to further improvements by stabilizing active cathode surface configurations.

25 ENERGY STORAGE↗

DOE OSTI2022

Catalytic and electrocatalytic performance of Sr(Ti 0.3 Fe 0.7 Ru 0.07 )O 3-δ for applications in solid oxide fuel cells supplied with ethanol steam reforming mixtures

We discuss how direct utilization of alcohols in Solid Oxide Fuel Cells (SOFCs) can improve the conversion efficiency by using excess heat for internal reforming and simplify the system balance of plant. Thanks to their scarce carbon- formation tendency, perovskite oxide anodes are promising alternatives to Ni-based cermets. Here we show that Sr(Ti 0.3 Fe 0.7 Ru 0.07 )O 3-δ (STF-Ru) exsolution anodes provide both catalytic reforming activity and electro- chemical activity with steam/ethanol (S/E) mixtures at 3:1 and 2:1 M ratio between 700 and 800 °C. Electrolyte- supported scandia stabilized zirconia SOFCs with STF-Ru anodes and Sr 0.95 Ti 0.3 Fe 0.7 O 3-δ (STF) cathodes are reasonably stable in the 3:1 S/E mixture over 20 h at 800 °C, with maximum power density of 195 mW/cm 2 and 140 mW/cm 2 at 0.7 V. Deactivation instead occurs with the 2:1 S/E mixture. Comparatively, cells with Ni-YSZ anodes rapidly coke and fail under the same conditions. Ethanol steam reforming experiments in a fixed bed powder reactor reveal that, above 650 °C, gas phase reactions convert ethanol to CO, hydrogen, acetaldehyde and ethylene, while STF-Ru catalyzes steam reforming. Thermogravimetric and Raman characterizations show that a moderate amount of carbon is deposited on the STF-Ru surface, which is more amorphous than the disruptive carbon which degrades Ni-YSZ.

09 BIOMASS FUELS↗

DOE OSTI2020

Domain-Matching Epitaxy of Ferroelectric Hf 0.5 Zr 0.5 O 2 (111) on La 2/3 Sr 1/3 MnO 3 (001)

Epitaxial ferroelectric HfO2 films are the most suitable to investigate intrinsic properties of the material and for prototyping emerging devices. Ferroelectric Hf 0.5 Zr 0.5 O 2 (111) films were epitaxially stabilized on La 2/3 Sr 1/3 MnO 3 (001) electrodes. This epitaxy, considering the symmetry dissimilarity and the huge lattice mismatch, is not compatible with conventional mechanisms of epitaxy. In this work, to gain insight into the epitaxy mechanism, scanning transmission electron microscopy characterization of the interface was performed, revealing arrays of dislocations with short periodicities. Additionally, these observed periodicities agree with those expected for domain matching epitaxy, indicating that this unconventional mechanism could be the prevailing factor in the stabilization of ferroelectric Hf0.5Zr0.5O2 with (111) orientation in the epitaxial Hf 0.5 Zr 0.5 O 2 (111)/La 2/3 Sr 1/3 MnO 3 (001)heterostructure.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Crystal and Electronic Structures of A 2 NaIO 6 Periodate Double Perovskites (A = Sr, Ca, Ba): Candidate Wasteforms for I-129 Immobilization

The synthesis, structure, and thermal stability of the periodate double perovskites A 2 NaIO 6 (A= Ba, Sr, Ca) were investigated in the context of potential application for the immobilization of radioiodine. A combination of X-ray diffraction and neutron diffraction, Raman spectroscopy, and DFT simulations were applied to determine accurate crystal structures of these compounds and understand their relative stability. The compounds were found to exhibit rock-salt ordering of Na and I on the perovskite B-site; Ba 2 NaIO 6 was found to adopt the Fm- 3 m aristotype structure, whereas Sr 2 NaIO 6 and Ca 2 NaIO 6 adopt the P 2 1 / n hettotype structure, characterized by cooperative octahedral tilting. DFT simulations determined the Fm- 3 m and P 2 1 / n structures of Ba 2 NaIO 6 to be energetically degenerate at room temperature, whereas diffraction and spectroscopy data evidence only the presence of the Fm- 3 m phase at room temperature, which may imply an incipient phase transition for this compound. The periodate double perovskites were found to exhibit remarkable thermal stability, with Ba 2 NaIO 6 only decomposing above 1050 °C in air, which is apparently the highest recorded decomposition temperature so far recorded for any iodine bearing compound. As such, these compounds offer some potential for application in the immobilization of iodine-129, from nuclear fuel reprocessing, with an iodine incorporation rate of 25–40 wt%. The synthesis of these compounds, elaborated here, is also compatible with both current conventional and future advanced processes for iodine recovery from the dissolver off-gas.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Deconvoluting the Magnetic Structure of the Commensurately Modulated Quinary Zintl Phase Eu 11– x Sr x Zn 4 Sn 2 As 12

The structure, magnetic properties, and 151 Eu and 119 Sn Mössbauer spectra of the solid-solution Eu 11– x Sr x Zn 4 Sn 2 As 12 are presented. A new commensurately modulated structure is described for Eu 11 Zn 4 Sn 2 As 12 ( R 3 m space group, average structure) that closely resembles the original structural description in the monoclinic C 2/ c space group with layers of Eu, puckered hexagonal Zn 2 As 3 sheets, and Zn 2 As 6 ethane-like isolated pillars. The solid-solution Eu 11– x Sr x Zn 4 Sn 2 As 12 (0 < x < 10) is found to crystallize in the commensurately modulated R 3 space group, related to the parent phase but lacking the mirror symmetry. Eu 11 Zn 4 Sn 2 As 12 orders with a saturation plateau at 1 T for 7 of the 11 Eu 2+ cations ferromagnetically coupled (5 K) and shows colossal magnetoresistance at 15 K. The magnetic properties of Eu 11 Zn 4 Sn 2 As 12 are investigated at higher fields, and the ferromagnetic saturation of all 11 Eu 2+ cations occurs at ~8 T. The temperature-dependent magnetic properties of the solid solution were investigated, and a nontrivial structure–magnetization correlation is revealed. The temperature-dependent 151 Eu and 119 Sn Mössbauer spectra confirm that the europium atoms in the structure are all Eu 2+ and that the tin is consistent with an oxidation state of less than four in the intermetallic region. The spectral areas of both Eu(II) and Sn increase at the magnetic transition, indicating a magnetoelastic effect upon magnetic ordering.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Structural and Electronic Effect Driven Distortions in Visible Light Absorbing Polar Materials A Ta 2 V 2 O 11 ( A = Sr, Pb)

Complex vanadates of tantalum(V), such as ATa 2 V 2 O 11 (A = Sr, Pb), are rare and underrated materials, which have potential application domains that could be substantially expanded, mitigating the existing controversy on their atomic and electronic organization. Herein, we present a thorough structural examination combining synchrotron powder X-ray diffraction-aided distortion mode analysis with computational methods to study hettotypes of SrTa 2 V 2 O 11 (STVO) and PbTa 2 V 2 O 11 (PTVO). Being distinct from the perovskite family due to the presence of [VO 4 ] groups, both compounds are polar dielectric materials with certain similarities to SBT and PBT Aurivillius phases. Applying the model of anions of metallic matrices to the analysis of electron localization functions calculated on top of as-established equilibrium structures helps retrace the effects in the Sr and Pb surroundings on the respective crystal packings of STVO and PTVO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Imaging Ferroelastic Domain Walls in Hybrid Improper Ferroelectric Sr 3 Sn 2 O 7

For this work, we combined synchrotron-based near field infrared spectroscopy and atomic force microscopy to image the properties of ferroelastic domain walls in Sr 3 Sn 2 O 7 . Although frequency shifts at the walls are near the limit of our sensitivity, we can confirm semiconducting rather than metallic character and widths between 20 and 60 nm. The latter is significantly narrower than in other hybrid improper ferroelectrics like Ca 3 Ti 2 O 7 . We attribute this trend to the softer lattice in Sr 3 Sn 2 O 7 , which may enable the octahedral tilt and rotation order parameters to evolve more quickly across the wall without significantly increased strain. These findings are crucial for the understanding of phononic properties at interfaces and the development of domain wall-based devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Unveiling the Degradation Mechanism of High-Temperature Superconductor Bi 2 Sr 2 CaCu 2 O 8+δ in Water-Bearing Environments

We report the physical properties of copper oxide high-temperature superconductors have been studied extensively, such as its band structure, and doping effects of Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212). However, some chemical-related properties of these superconductors are rarely reported, such as their stability in air. Here, we report experiments combined with ab initio calculations that address the effects of water in contact with Bi-2212. The evolution of Bi-2212 flake with exposure to water for different time intervals were tested and characterized by optical microscopy (OM), atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM) and electrical measurements. The thickness of Bi-2212 flakes is gradually decreased in water, and some thin flakes can be completely etched away after a few days. The stability of Bi-2212 in other solvents is also evaluated, including alcohol, acetone, HCl and KOH. The morphology of Bi-2212 flakes is relatively stable in organic solvents. However, the flakes are etched relatively quick in HCl and KOH, especially in acidic environment. Our results imply that hydrogen ion is primarily responsible for the deterioration of their properties. Both TEM and calculation results demonstrate that the atoms in Bi-O plane is relatively stable when compared to the inner atoms in Sr-O, Ca-O and Cu-O planes. This work contributes towards understanding the chemical stability of Bi-2212 superconducting device in environmental medium, which is important for both fundamental studies and practical applications of copper oxide high-temperature superconductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗