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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sr(BiPd)2 by Materials Project

SrPd2Bi2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Sr is bonded in a 1-coordinate geometry to eight Pd and nine Bi atoms. There are a spread of Sr–Pd bond distances ranging from 3.29–3.90 Å. There are a spread of Sr–Bi bond distances ranging from 3.63–3.92 Å. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Sr and five Bi atoms. There are a spread of Pd–Bi bond distances ranging from 2.74–2.86 Å. In the second Pd site, Pd is bonded in a 10-coordinate geometry to four equivalent Sr, two equivalent Pd, and four equivalent Bi atoms. Both Pd–Pd bond lengths are 3.07 Å. There are a spread of Pd–Bi bond distances ranging from 2.77–2.84 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 5-coordinate geometry to five equivalent Sr and five Pd atoms. In the second Bi site, Bi is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(PN2)2 by Materials Project

Sr(PN2)2 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. there are six inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven N3- atoms. There are a spread of Sr–N bond distances ranging from 2.57–3.15 Å. In the second Sr2+ site, Sr2+ is bonded in a 12-coordinate geometry to twelve N3- atoms. There are a spread of Sr–N bond distances ranging from 2.72–3.22 Å. In the third Sr2+ site, Sr2+ is bonded in a 4-coordinate geometry to four N3- atoms. There are a spread of Sr–N bond distances ranging from 2.54–2.65 Å. In the fourth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine N3- atoms. There are a spread of Sr–N bond distances ranging from 2.68–2.90 Å. In the fifth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine N3- atoms. There are a spread of Sr–N bond distances ranging from 2.69–2.90 Å. In the sixth Sr2+ site, Sr2+ is bonded in a 4-coordinate geometry to four N3- atoms. There are a spread of Sr–N bond distances ranging from 2.58–2.61 Å. There are eight inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There is one shorter (1.57 Å) and three longer (1.65 Å) P–N bond length. In the second P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There is three shorter (1.64 Å) and one longer (1.65 Å) P–N bond length. In the third P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There are a spread of P–N bond distances ranging from 1.63–1.65 Å. In the fourth P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There are a spread of P–N bond distances ranging from 1.58–1.66 Å. In the fifth P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There is three shorter (1.64 Å) and one longer (1.66 Å) P–N bond length. In the sixth P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There is three shorter (1.64 Å) and one longer (1.66 Å) P–N bond length. In the seventh P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There are a spread of P–N bond distances ranging from 1.63–1.66 Å. In the eighth P5+ site, P5+ is bonded to four N3- atoms to form corner-sharing PN4 tetrahedra. There are a spread of P–N bond distances ranging from 1.63–1.66 Å. There are sixteen inequivalent N3- sites. In the first N3- site, N3- is bonded in a linear geometry to one Sr2+ and two P5+ atoms. In the second N3- site, N3- is bonded in a 2-coordinate geometry to two Sr2+ and two P5+ atoms. In the third N3- site, N3- is bonded in a 2-coordinate geometry to one Sr2+ and two P5+ atoms. In the fourth N3- site, N3- is bonded in a 3-coordinate geometry to one Sr2+ and two P5+ atoms. In the fifth N3- site, N3- is bonded in a 3-coordinate geometry to two Sr2+ and two P5+ atoms. In the sixth N3- site, N3- is bonded in a 3-coordinate geometry to one Sr2+ and two P5+ atoms. In the seventh N3- site, N3- is bonded in a 2-coordinate geometry to two Sr2+ and two P5+ atoms. In the eighth N3- site, N3- is bonded in a distorted trigonal planar geometry to one Sr2+ and two P5+ atoms. In the ninth N3- site, N3- is bonded in a 3-coordinate geometry to two Sr2+ and two P5+ atoms. In the tenth N3- site, N3- is bonded in a 3-coordinate geometry to one Sr2+ and two P5+ atoms. In the eleventh N3- site, N3- is bonded in a 4-coordinate geometry to two Sr2+ and two P5+ atoms. In the twelfth N3- site, N3- is bonded in a 4-coordinate geometry to two Sr2+ and two P5+ atoms. In the thirteenth N3- site, N3- is bonded in a 2-coordinate geometry to two Sr2+ and two P5+ atoms. In the fourteenth N3- site, N3- is bonded in a 3-coordinate geometry to one Sr2+ and two P5+ atoms. In the fifteenth N3- site, N3- is bonded in a 2-coordinate geometry to two Sr2+ and two P5+ atoms. In the sixteenth N3- site, N3- is bonded in a 2-coordinate geometry to two equivalent Sr2+ and two P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(BiPd)2 by Materials Project

SrPd2Bi2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Sr is bonded in a 4-coordinate geometry to eight Pd and eight Bi atoms. There are four shorter (3.58 Å) and four longer (3.77 Å) Sr–Pd bond lengths. There are four shorter (3.72 Å) and four longer (3.75 Å) Sr–Bi bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 8-coordinate geometry to four equivalent Sr and four equivalent Bi atoms. All Pd–Bi bond lengths are 2.79 Å. In the second Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Sr and five Bi atoms. There are one shorter (2.73 Å) and four longer (2.83 Å) Pd–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Pd atoms. In the second Bi site, Bi is bonded in a 5-coordinate geometry to four equivalent Sr and five Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(H8O5)2 by Materials Project

Sr(H8O5)2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Sr is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.69 Å. There are eight inequivalent H sites. In the first H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.03 Å) and one longer (1.57 Å) H–O bond length. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.97 Å. In the third H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.01 Å) and one longer (1.67 Å) H–O bond length. In the fourth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the fifth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the sixth H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.01 Å) and one longer (1.67 Å) H–O bond length. In the seventh H site, H is bonded in a distorted linear geometry to two O atoms. There is one shorter (1.02 Å) and one longer (1.65 Å) H–O bond length. In the eighth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. There are five inequivalent O sites. In the first O site, O is bonded in a 5-coordinate geometry to four H and one O atom. The O–O bond length is 1.50 Å. In the second O site, O is bonded in a distorted water-like geometry to one Sr and two H atoms. In the third O site, O is bonded in a water-like geometry to one Sr and two H atoms. In the fourth O site, O is bonded in a water-like geometry to one Sr and two H atoms. In the fifth O site, O is bonded in a distorted water-like geometry to one Sr and two H atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(SO5)2 by Materials Project

Sr(SO5)2 crystallizes in the hexagonal P6_2 space group. The structure is one-dimensional and consists of one Sr(SO5)2 ribbon oriented in the (0, 0, 1) direction. Sr is bonded in a 4-coordinate geometry to six O atoms. There are four shorter (2.47 Å) and two longer (3.23 Å) Sr–O bond lengths. S is bonded in a trigonal non-coplanar geometry to three O atoms. There is one shorter (1.44 Å) and two longer (1.48 Å) S–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one O atom. The O–O bond length is 1.23 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one Sr and one S atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Sr and one S atom. In the fourth O site, O is bonded in a single-bond geometry to one S atom. In the fifth O site, O is bonded in a distorted single-bond geometry to one Sr and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(TlHg)2 by Materials Project

Sr(HgTl)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Sr is bonded in a 12-coordinate geometry to eight Hg and four equivalent Tl atoms. There are a spread of Sr–Hg bond distances ranging from 3.58–3.70 Å. All Sr–Tl bond lengths are 3.65 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a 9-coordinate geometry to four equivalent Sr, three Hg, and two equivalent Tl atoms. There are two shorter (2.91 Å) and one longer (2.92 Å) Hg–Hg bond lengths. Both Hg–Tl bond lengths are 3.17 Å. In the second Hg site, Hg is bonded in a 8-coordinate geometry to four equivalent Sr, two equivalent Hg, and two equivalent Tl atoms. Both Hg–Tl bond lengths are 3.14 Å. Tl is bonded in a 2-coordinate geometry to two equivalent Sr, two Hg, and five equivalent Tl atoms. There are one shorter (3.20 Å) and four longer (3.38 Å) Tl–Tl bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(AlAu)2 by Materials Project

SrAu2Al2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Sr is bonded in a 8-coordinate geometry to eight Au and eight Al atoms. There are four shorter (3.45 Å) and four longer (3.47 Å) Sr–Au bond lengths. There are four shorter (3.46 Å) and four longer (3.48 Å) Sr–Al bond lengths. There are two inequivalent Au sites. In the first Au site, Au is bonded to four equivalent Sr and four equivalent Al atoms to form distorted AuSr4Al4 tetrahedra that share corners with twelve equivalent AlSr4Au4 tetrahedra, edges with two equivalent AlSr4Au4 tetrahedra, edges with four equivalent AuSr4Al4 tetrahedra, and faces with four equivalent AuSr4Al4 tetrahedra. All Au–Al bond lengths are 2.62 Å. In the second Au site, Au is bonded in a 9-coordinate geometry to four equivalent Sr and five Al atoms. There are one shorter (2.58 Å) and four longer (2.65 Å) Au–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Sr and four equivalent Au atoms to form distorted AlSr4Au4 tetrahedra that share corners with twelve equivalent AuSr4Al4 tetrahedra, edges with two equivalent AuSr4Al4 tetrahedra, edges with four equivalent AlSr4Au4 tetrahedra, and faces with four equivalent AlSr4Au4 tetrahedra. In the second Al site, Al is bonded in a 5-coordinate geometry to four equivalent Sr and five Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(ZnSn)2 by Materials Project

SrZn2Sn2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Sr is bonded in a 4-coordinate geometry to eight Zn and eight Sn atoms. There are a spread of Sr–Zn bond distances ranging from 3.53–3.78 Å. There are a spread of Sr–Sn bond distances ranging from 3.51–3.77 Å. There are two inequivalent Zn sites. In the first Zn site, Zn is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. There are a spread of Zn–Sn bond distances ranging from 2.65–2.85 Å. In the second Zn site, Zn is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Sn atoms. There are a spread of Zn–Sn bond distances ranging from 2.75–2.81 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Sr and five Zn atoms. In the second Sn site, Sn is bonded to four equivalent Sr and four equivalent Zn atoms to form a mixture of distorted edge and face-sharing SnSr4Zn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(NO5)2 by Materials Project

Sr(NO3)2(O2)2 crystallizes in the monoclinic C2/c space group. The structure is one-dimensional and consists of eight hydrogen peroxide molecules and two Sr(NO3)2 ribbons oriented in the (1, 0, 1) direction. In each Sr(NO3)2 ribbon, Sr is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.73 Å. N is bonded in a trigonal planar geometry to three O atoms. There are a spread of N–O bond distances ranging from 1.23–1.32 Å. There are three inequivalent O sites. In the first O site, O is bonded in a distorted water-like geometry to one Sr and one N atom. In the second O site, O is bonded in a 1-coordinate geometry to two equivalent Sr and one N atom. In the third O site, O is bonded in a single-bond geometry to one N atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(ClO3)2 by Materials Project

Sr(O3Cl)2 crystallizes in the monoclinic C2 space group. The structure is one-dimensional and consists of two Sr(O3Cl)2 ribbons oriented in the (0, 0, 1) direction. Sr is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Sr–O bond distances ranging from 2.46–2.57 Å. There are four inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one O and one Cl atom. The O–O bond length is 1.34 Å. The O–Cl bond length is 1.81 Å. In the second O site, O is bonded in a 3-coordinate geometry to one Sr and two equivalent O atoms. Both O–O bond lengths are 1.80 Å. In the third O site, O is bonded in a distorted T-shaped geometry to two equivalent Sr and one O atom. In the fourth O site, O is bonded in a 4-coordinate geometry to two equivalent Sr and two equivalent O atoms. Cl is bonded in a single-bond geometry to one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Kinetics and Thermodynamics of Sr Permeation in CeO 2 -Based Barrier Layers for Solid-Oxide Electrolyzer Cells

Solid-oxide electrolyzer cells (SOECs) convert steam to hydrogen efficiently at high temperatures. However, during operation, the diffusion of cations or impurities through the cells due to electrode degradation can cause unwanted secondary phases to form, which may degrade device performance. Here, in this study, we use atomistic and mesoscale simulations coupled with experimental analysis to study the diffusion of Sr through the Gd-doped CeO 2 (GDC) barrier layer used to protect the yttria-stabilized zirconia (YSZ) electrolyte in SOECs. From our atomistic calculations, we find Sr diffusion to be negligibly slow in bulk GDC; however, surface diffusion is much more favorable. Subsequent mesoscale simulations show that Sr diffusion is activated when the porosity of GDC exceeds ∼10% and significantly exceeds diffusion in bulk and grain boundary regions. We also find that SrO-based species can accumulate at GDC surfaces; however, SrO aggregation and coarsening will be limited by the large lattice mismatch between GDC and SrO. Energy-dispersive X-ray spectroscopy (EDS) and electron diffraction confirm that Sr can accumulate within GDC pores and form disperse Sr-containing secondary phases. Altogether, Sr diffusion in dense GDC is unlikely to give rise to thick SrO layers, which would severely limit device performance. The formation of Sr-containing secondary phases can largely be avoided by restricting the porosity of the GDC layer as much as possible.

36 MATERIALS SCIENCE↗
DOE OSTI2021

In situ EXAFS study of Sr adsorption on TiO 2 (110) under high ionic strength wastewater conditions

In order to provide important details concerning the adsorption reactions of Sr, batch reactions and a set of both ex situ and in situ Grazing Incidence X-ray Absorption Fine Structure (GIXAFS) adsorption experiments were completed on powdered TiO 2 and on rutile(110), both reacted with either SrCl 2 or SrCO 3 solutions. TiO 2 sorption capacity for strontium (Sr) ranges from 550 ppm (SrCl 2 solutions, second order kinetics) to 1400 ppm (SrCO 3 solutions, first order kinetics), respectively, and is rapid. Sr adsorption decreased as a function of chloride concentration but significantly increased as carbonate concentrations increased. In the presence of carbonate, the ability of TiO 2 to remove Sr from the solution increases by a factor of ~4 due to rapid epitaxial surface precipitation of an SrCO 3 thin film, which registers itself on the rutile(110) surface as a strontianite-like phase (d-spacing 2.8 Å). Extended X-ray Absorption Fine Structure (EXAFS) results suggest the initial attachment is via tetradental inner-sphere Sr adsorption. Moreover, adsorbates from concentrated SrCl 2 solutions contain carbonate and hydroxyl species, which results in both inner- and outer-sphere adsorbates and explains the reduced Sr adsorption in these systems. These results not only provide new insights into Sr kinetics and adsorption on TiO 2 but also provide valuable information concerning potential improvements in effluent water treatment models and are pertinent in developing treatment methods for rutile-coated structural materials within nuclear power plants.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Non-Centrosymmetric Sr 2 IrO 4 Obtained Under High Pressure

Sr 2 IrO 4 with strong spin-orbit coupling (SOC) and Hubbard repulsion (U) hosts Mott insulating states. The similar crystal structure, magnetic and electronic properties, particularly the d-wave gap observed in Sr 2 IrO 4 enhanced the analogies to cuprate high-$T_c$ superconductor, La 2 CuO 4 . The incomplete analogy was due to the lack of broken inversion symmetry phases observed in Sr 2 IrO 4 . Here, under high pressure and high temperature conditions, we report a non-centrosymmetric Sr 2 IrO 4 . The crystal structure and its noncentrosymmetric character were determined by single crystal X-ray diffraction and high-resolution scanning transmission electron microscopy (HR-STEM). The magnetic characterization confirms the Ir 4+ with $\textit{S}$ = 1/2 at low temperature in Sr 2 IrO 4 with magnetic ordering occurred at around 86 K, where a larger moment is observed than the ambient pressure Sr 2 IrO 4 . Moreover, the resistivity measurement shows three-dimensional Mott variable-range hopping existed in the system. Further, this non-centrosymmetric Sr 2 IrO 4 phase appears to be a unique material to offer further understanding of high-$T_c$ superconductivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Combinatorial screening of crystal structure in Ba-Sr-Mn-Ce perovskite oxides with ABO 3 stoichiometry

ABO 3 oxides with the perovskite-related structures are attracting significant interest due to their promising physical and chemical properties for many applications requiring tunable chemistry, including fuel cells, catalysis, and electrochemical water splitting. Here we report on the crystal structure of the entire family of perovskite oxides with ABO 3 stoichiometry, where A and B are Ba, Sr, Mn, Ce. Given the vast size of this chemically complex material system, exploration for stable perovskite-related structures with respect to its constituent elements and annealing temperature is performed by combinatorial pulsed laser deposition and spatially-resolved characterization of composition and structure. As a result of this high-throughput experimental study, we identify hexagonal perovskite-related polytypic transformation as a function of composition in the Ba 1-x Sr x MnO 3 oxides after annealing at different temperatures. Furthermore, a hexagonal perovskite-related polytype is observed in a narrow composition-temperature range of the Ba 1-x Sr x MnO 3 oxides. In contrast, a tetragonally-distorted perovskite is observed across a wider range of compositions and annealing temperatures in the Sr 1-x Ce x MnO 3 oxides. This structure stability is further enhanced along the Ba 1-x Sr x MnO 3 - Sr 1-x Ce x MnO 3 pseudo-binary tie-line at x=0.25 by increasing Ba-incorporation and annealing temperature. These results indicate that the BaCe x Mn 1-x O 3 - Sr 1-x Ce x MnO 3 pseudo-binary oxide alloys (solid solutions) with tetragonal perovskite structure and broad composition-temperature range of stability are promising candidates for thermochemical water splitting applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nuclear level density and γ -decay strength of Sr 93

This work presents the first experimentally determined nuclear level density and γ-ray strength function of the short-lived fission product 93 Sr, accomplished using the β-Oslo method. Direct measurement of the 92 Sr(n, γ) 93 Sr cross section is not currently possible, as the half-life of 2.66 hours is too short; instead, 93 Sr was formed through β decay of 93 Rb to excitation energies around the neutron separation energy. The γ-ray spectra were measured using a total absorption spectrometer at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). The statistical properties of the 93 Sr nucleus were experimentally determined, including the γ-ray strength function and nuclear level density. At low energies, the γ-ray strength function exhibits a constant γ-decay strength, rather than a slightly increasing strength with decreasing γ-ray energy as had been previously observed for several nuclei in this mid-mass region. Finally, these statistical properties were then implemented in the reaction code TALYS1.95 to calculate the 92 Sr(n, γ) 93 Sr cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Magnetic polarons and spin-glass behavior in insulating La 1-x Sr x CoO 3 (x = 0.125 and 0.15)

The evolution of magnetic polarons in Sr doped La Co O 3 ( La 1 - x Sr x Co O 3 ) single crystal and polycrystalline samples are investigated by employing dc and ac magnetic measurement and small angle neutron scattering (SANS) techniques. The effect of magnetic field and temperature on magnetic polarons is experimentally studied for La 0.875 Sr 0.125 Co O 3 and La 0.85 Sr 0.15 Co O 3 compounds that belong to the spin glass insulating regime of the broader compositional phase diagram of this system. Langevin analyses of the isothermal magnetization curves in the notional paramagnetic regime prove the existence of magnetic polarons with large moments. The dc field superimposed ac susceptibility data and the analysis of the glassy dynamics prove that the size of polarons in 15% Sr doped crystal increase as the field is increased while the field effect is not visible in the 12.5% Sr doped crystal. A polycrystalline sample of La 0.85 Sr 0.15 Co O 3 is analyzed by SANS experiments, which confirm nonzero correlation length at temperatures far above the macroscopic ordering temperature and hence the presence of magnetic polarons.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Understanding the Degradation of La 1−x Sr x FeO 3−δ (0 ≤ x ≤ 1) Perovskite Oxides during the Oxygen Evolution Reaction in Alkaline Solution

Perovskite oxides are an emerging class of highly active catalysts for the oxygen evolution reaction (OER); however, their electrochemical stability remains poorly understood. Here, we report a systematic evaluation of the OER activity and stability of La 1−x Sr x FeO 3-δ perovskites in 1 M KOH. Their initial OER activity first increases with increasing Sr content (fromx= 0 to 0.8), and then decreases when the Sr content is increased to 1. Their stability evaluated by monitoring the element leaching from the electrodes show that La does not leach at a detectable rate, but Sr and Fe leach substantially. The leaching of Sr occurs at similar rates under open circuit potential (OCP) and OER potential, suggesting a nonelectrochemical dissolution process. The leaching of Fe is, however, strongly dependent on the electrode potential. More Fe leaching is observed under the OER potential than OCP. Additionally, the electrode with higher initial OER activity leaches more Fe. These results indicate that OER facilitates the dissolution of Fe from the electrode. The leaching of Fe, in turn, is considered responsible for the activity loss of La 1-x Sr x FeO 3−δ during OER. This study brings new insight into the degradation mechanism of La 1-x Sr x FeO 3−δ and their related perovskite oxides during electro-oxidation processes.

Electrochemistry↗
NASA NTRS1990

The effect of Sr and Bi on the Si(100) surface oxidation - Auger electron spectroscopy, low energy electron diffraction, and X-ray photoelectron spectroscopy study

The effect of Sr and Bi on the oxidation of the Si(100) surface has been studied by Auger electron spectroscopy, low electron diffraction, and X-ray photoelectron spectroscopy. A dramatic enhancement, by a factor of 10, of the Si oxidation has been observed for Si(100) with a Sr overlayer. The SR-enhanced Si oxidation has been studied as a function of O2 exposure and Sr coverage. In contrast to the oxidation promotion of Sr on Si, it has been also observed that a Bi overlayer on Si(100) reduced Si oxidation significantly. Sr adsorption on the Si(100) with a Bi overlayer enhances Si oxidation only at Sr coverage of greater than 0.3 ML.

Fan, W. C.↗