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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Structural and phonon anomalies in the superconducting Bi 2 Sr 2 CaCu 2 O 8+σ with varying doping level at high pressures

Here we examined the effect of the lattice compression on the crystal structure of the Bi 2 Sr 2 CaCu 2 O 8+σ superconductor with nearly optimally doped and overdoped composition using X-ray diffraction technique. Our studies show that at high pressures (up to 30 GPa ) the doping level does not affect the crystal structure of this superconductor. Along with this, structural anomalies in ratio appear at a pressure that corresponds to that at which T c begins to decrease. This fact indicates a close connection between the observed anomalies and superconductivity. We also studied the effect of doping and pressure on the T c (P) and on the Raman active lattice modes of the Bi 2 Sr 2 CaCu 2 O 8+σ superconductors. We find universal suppression of the T c by the pressure starting from the critical pressure P c in the range from 9 to 16 GPa, depending on the doping level of the Bi 2 Sr 2 CaCu 2 O 8+σ samples. Concomitantly, we observe phonon anomalies around 10 to 20 GPa, which indicate possible pressure-induced charge redistribution in BiO layers. These newly detected anomalies may be related to the changes in the electronic structure which compete with the superconductivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Theoretical study of CO2 capture mechanisms of SrO and Sr(OH)2.nH2O (n=0,1,8)

This presentation encapsulated the use of density functional theory (DFT) to investigate the mechanism of CO2 conversion on various crystal surfaces, including SrO, Sr(OH)2, Sr(OH)2·H2O, and Sr(OH)2·8H2O. The study provides unique insights into the fundamental mechanism for CO2 capture using SrO and its hydrated forms.

catalyst performance↗
DOE OSTI2020

Flexible Magnetic Polymer Composite Substrate with Ba 1.5 Sr 1.5 Z Hexaferrite Particles of VHF/Low UHF Patch Antennas for UAVs and Medical Implant Devices

Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε), have attracted great attention, because they facilitate miniaturization of microwave devices while keeping or enhancing electromagnetic characteristics. Mechanically millled Ba 1.5 Sr 1.5 Co 2 Fe 24 O 41 (Ba 1.5 Sr 1.5 Z) hexaferrite particles were used to increase permeability in the interesting frequency band. The microwave properties of Ba 1.5 Sr 1.5 Z composites were predicted and measured. Hansen’s zero-order analysis of antenna bandwidth and electromagnetic field simulation showed that the hexaferrite-based flexible composite could enhance a bandwidth and achieve the miniaturization of antennas as well. The magnetic antenna substrates can be a good solution to integrate antennas into the UAVs whose dimensions are comparable to or larger than communication wavelength.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk

High-contrast imaging of exoplanets and protoplanetary disks depends on wave front sensing and correction made by adaptive optics instruments. Classically, wave front sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wave front sensor (PWFS). With this new module we observed SR 21, a young star that is brighter at NIR wavelengths than at optical wavelengths. Compared with the archival data of SR 21 taken with the optical wave front sensing we achieved ~20% better Strehl ratio in similar natural seeing conditions. Further post-processing utilizing angular differential imaging and reference-star differential imaging confirmed the spiral feature reported by the Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch instrument polarimetric observation, which is the first detection of the SR 21 spiral in total intensity at L' band. We also compared the contrast limit of our result (10 -4 at 0.'4 and 2 × 10 -5 at 1.'0) with the archival data that were taken with optical wave front sensing and confirmed the improvement, particularly at ≤0.'5. Our observation demonstrates that the NIR PWFS improves AO performance and will provide more opportunities for red targets in the future.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Hard x-ray standing-wave photoemission study of the interfaces in a BiFeO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ superlattice

Hybrid multiferroics such as BiFeO$_3$ (BFO) and La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) heterostructures are highly interesting functional systems due to their complex electronic and magnetic properties. One of the key parameters influencing the emergent properties is the quality of interfaces, where varying interdiffusion lengths can give rise to different chemistry and distinctive electronic states. Here we report high-resolution depth resolved chemical and electronic investigation of BFO/LSMO superlattice using standing-wave hard X-ray photoemission spectroscopy in the first-order Bragg as well as near-total-reflection geometry. Our results show that the interfaces of BFO on top of LSMO are atomically abrupt, while the LSMO on top of BFO interfaces show an interdiffusion length of around 1.2 unit cells. The two interfaces also exhibit different chemical gradients, with the BFO/LSMO interface being Sr-terminated by a spectroscopically distinctive high binding energy component in Sr 2p core-level spectra, which is spatially contained within 1 unit cell from the interface. From the electronic point of view, unique valence band features were observed for bulk-BFO, bulk-LSMO and their interfaces. Our X-ray optical analysis revealed a unique electronic signature at the BFO/LSMO interface, which we attribute to the coupling between those respective layers. Valence band decomposition based on the Bragg-reflection standing-wave measurement also revealed the band alignment between BFO and LSMO layers. Our work demonstrates that standing-wave hard x-ray photoemission is a reliable non-destructive technique for probing depth-resolved electronic structure of buried layers and interfaces with sub-unit-cell resolution. Equivalent investigations can be successfully applied to a broad class of material such as perovskite complex oxides with emergent interfacial phenomena.

Martins, HP↗
DOE OSTI2020

Experimental Study on the Transfer of Cs, Sr, Pu and Water in Concrete for the Estimation of Contamination - 20085

As part of the 'Nuclear Energy Science and Technology and Human Resources Development project- through concentrating wisdom-by MEXT' in Japan, the major results from the second year of a project on the analysis of radionuclide contamination mechanisms of concrete and the estimation of contamination distribution at the Fukushima Daiichi nuclear power station active during 2018-2020 are presented. The transfer of Cs, Sr, Pu, and water through concrete was studied experimentally. In a saturated condition, the clay did not affect the transfer and Cs penetrated much faster than Sr. In the dried condition, clay retarded Cs transfer. Carbonation of the concrete retarded the transfer of Cs and Sr. Pu was expected to be precipitated immediately in a high pH condition of concrete. Water suction depends on the temperature. Further, the detailed mechanism was analyzed by {sup 1}H-NMR. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Sr(BeN)2 by Materials Project

Sr(BeN)2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. All Sr–N bond lengths are 2.83 Å. Be2+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. There is one shorter (1.63 Å) and two longer (1.67 Å) Be–N bond length. N3- is bonded in a 7-coordinate geometry to four equivalent Sr2+ and three equivalent Be2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(As3Pt2)2 by Materials Project

Sr(Pt2As3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr2+ is bonded to six Pt2- atoms to form distorted corner-sharing SrPt6 pentagonal pyramids. There are a spread of Sr–Pt bond distances ranging from 2.99–3.18 Å. There are three inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded to six As1+ atoms to form corner-sharing PtAs6 octahedra. The corner-sharing octahedra tilt angles range from 60–65°. There are two shorter (2.52 Å) and four longer (2.53 Å) Pt–As bond lengths. In the second Pt2- site, Pt2- is bonded to two equivalent Sr2+ and four As1+ atoms to form PtSr2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four PtSr2As4 octahedra. The corner-sharing octahedra tilt angles range from 20–108°. There are a spread of Pt–As bond distances ranging from 2.48–2.54 Å. In the third Pt2- site, Pt2- is bonded to two equivalent Sr2+ and four As1+ atoms to form PtSr2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four equivalent PtSr2As4 octahedra. The corner-sharing octahedra tilt angles range from 30–83°. There are two shorter (2.47 Å) and two longer (2.53 Å) Pt–As bond lengths. There are three inequivalent As1+ sites. In the first As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms. In the second As1+ site, As1+ is bonded in a trigonal planar geometry to three Pt2- atoms. In the third As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(Ni5P3)2 by Materials Project

Sr(Ni5P3)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Sr2+ is bonded in a 12-coordinate geometry to eight P3- atoms. There are a spread of Sr–P bond distances ranging from 3.20–3.56 Å. There are four inequivalent Ni+1.60+ sites. In the first Ni+1.60+ site, Ni+1.60+ is bonded in a distorted rectangular see-saw-like geometry to four P3- atoms. There are a spread of Ni–P bond distances ranging from 2.31–2.46 Å. In the second Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of distorted edge and corner-sharing NiP4 tetrahedra. There are two shorter (2.25 Å) and two longer (2.34 Å) Ni–P bond lengths. In the third Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.17–2.30 Å. In the fourth Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.20–2.32 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 6-coordinate geometry to two equivalent Sr2+ and six Ni+1.60+ atoms. In the second P3- site, P3- is bonded in a 6-coordinate geometry to one Sr2+ and six Ni+1.60+ atoms. In the third P3- site, P3- is bonded in a 9-coordinate geometry to one Sr2+ and eight Ni+1.60+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(NiO2)4 by Materials Project

Sr(NiO2)4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Sr2+ is bonded in a distorted hexagonal planar geometry to six equivalent O2- atoms. All Sr–O bond lengths are 2.52 Å. There are two inequivalent Ni+3.50+ sites. In the first Ni+3.50+ site, Ni+3.50+ is bonded to six equivalent O2- atoms to form edge-sharing NiO6 octahedra. All Ni–O bond lengths are 2.02 Å. In the second Ni+3.50+ site, Ni+3.50+ is bonded to six O2- atoms to form edge-sharing NiO6 octahedra. There is four shorter (1.89 Å) and two longer (1.91 Å) Ni–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Sr2+ and three Ni+3.50+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Ni+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(InTe2)2 by Materials Project

Sr(InTe2)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are four shorter (3.51 Å) and four longer (3.58 Å) Sr–Te bond lengths. In3+ is bonded to four Te2- atoms to form edge-sharing InTe4 tetrahedra. There are a spread of In–Te bond distances ranging from 2.83–2.88 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two equivalent In3+ atoms. In the second Te2- site, Te2- is bonded to two equivalent Sr2+ and two equivalent In3+ atoms to form a mixture of distorted corner and edge-sharing TeSr2In2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(Sb3Ru)4 by Materials Project

Sr(RuSb3)4 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Sr2+ is bonded to twelve equivalent Sb1- atoms to form SrSb12 cuboctahedra that share faces with eight equivalent RuSb6 octahedra. All Sr–Sb bond lengths are 3.56 Å. Ru+2.50+ is bonded to six equivalent Sb1- atoms to form RuSb6 octahedra that share corners with six equivalent RuSb6 octahedra and faces with two equivalent SrSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 55°. All Ru–Sb bond lengths are 2.65 Å. Sb1- is bonded in a 2-coordinate geometry to one Sr2+, two equivalent Ru+2.50+, and two equivalent Sb1- atoms. There are one shorter (2.97 Å) and one longer (3.00 Å) Sb–Sb bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(Ag3O2)2 by Materials Project

Sr(Ag3O2)2 crystallizes in the orthorhombic Pnna space group. The structure is three-dimensional. Sr2+ is bonded to six O2- atoms to form edge-sharing SrO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.49–2.73 Å. There are four inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a linear geometry to two O2- atoms. There are one shorter (2.11 Å) and one longer (2.12 Å) Ag–O bond lengths. In the second Ag1+ site, Ag1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.42 Å) and two longer (2.90 Å) Ag–O bond lengths. In the third Ag1+ site, Ag1+ is bonded in a bent 150 degrees geometry to two O2- atoms. There are one shorter (2.14 Å) and one longer (2.16 Å) Ag–O bond lengths. In the fourth Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.13 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Sr2+ and four Ag1+ atoms. In the second O2- site, O2- is bonded to two equivalent Sr2+ and three Ag1+ atoms to form a mixture of distorted edge and corner-sharing OSr2Ag3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(NiP)2 by Materials Project

SrNi2P2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a distorted body-centered cubic geometry to eight P3- atoms. There are four shorter (3.16 Å) and four longer (3.19 Å) Sr–P bond lengths. In the second Sr2+ site, Sr2+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Sr–P bond lengths are 3.24 Å. There are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to four P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. There are three shorter (2.25 Å) and one longer (2.28 Å) Ni–P bond lengths. In the second Ni2+ site, Ni2+ is bonded to four P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. There are two shorter (2.28 Å) and two longer (2.29 Å) Ni–P bond lengths. There are two inequivalent P3- sites. In the first P3- site, P3- is bonded in a 4-coordinate geometry to four Sr2+ and four Ni2+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to four equivalent Sr2+, four Ni2+, and one P3- atom. The P–P bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(MnSb)2 by Materials Project

Sr(MnSb)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent Sb3- atoms to form SrSb6 octahedra that share corners with twelve equivalent MnSb4 tetrahedra, edges with six equivalent SrSb6 octahedra, and edges with six equivalent MnSb4 tetrahedra. All Sr–Sb bond lengths are 3.38 Å. Mn2+ is bonded to four equivalent Sb3- atoms to form MnSb4 tetrahedra that share corners with six equivalent SrSb6 octahedra, corners with six equivalent MnSb4 tetrahedra, edges with three equivalent SrSb6 octahedra, and edges with three equivalent MnSb4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–51°. There are three shorter (2.77 Å) and one longer (2.78 Å) Mn–Sb bond lengths. Sb3- is bonded to three equivalent Sr2+ and four equivalent Mn2+ atoms to form a mixture of distorted corner and edge-sharing SbSr3Mn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(C2N3)2 by Materials Project

Sr(C2N3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight N3- atoms. There are a spread of Sr–N bond distances ranging from 2.63–2.95 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.30 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.31 Å) C–N bond length. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted single-bond geometry to two equivalent Sr2+ and one C4+ atom. In the second N3- site, N3- is bonded in a distorted bent 120 degrees geometry to one Sr2+ and two C4+ atoms. In the third N3- site, N3- is bonded in a distorted bent 150 degrees geometry to one Sr2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(Mo3S4)2 by Materials Project

Sr(Mo3S4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Sr2+ is bonded in a body-centered cubic geometry to eight S2- atoms. There are two shorter (2.86 Å) and six longer (3.17 Å) Sr–S bond lengths. Mo+2.33+ is bonded to five S2- atoms to form a mixture of corner and edge-sharing MoS5 square pyramids. There are a spread of Mo–S bond distances ranging from 2.40–2.60 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one Sr2+ and three equivalent Mo+2.33+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to one Sr2+ and four equivalent Mo+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(CeS2)2 by Materials Project

Sr(CeS2)2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Sr2+ is bonded to eight equivalent S2- atoms to form distorted SrS8 hexagonal bipyramids that share corners with eight equivalent CeS8 hexagonal bipyramids, edges with four equivalent SrS8 hexagonal bipyramids, and faces with eight equivalent CeS8 hexagonal bipyramids. There are four shorter (2.96 Å) and four longer (3.14 Å) Sr–S bond lengths. Ce3+ is bonded to eight equivalent S2- atoms to form distorted CeS8 hexagonal bipyramids that share corners with four equivalent SrS8 hexagonal bipyramids, corners with four equivalent CeS8 hexagonal bipyramids, edges with four equivalent CeS8 hexagonal bipyramids, faces with four equivalent SrS8 hexagonal bipyramids, and faces with four equivalent CeS8 hexagonal bipyramids. There are a spread of Ce–S bond distances ranging from 2.87–3.11 Å. S2- is bonded to two equivalent Sr2+ and four equivalent Ce3+ atoms to form a mixture of distorted edge, corner, and face-sharing SSr2Ce4 octahedra. The corner-sharing octahedra tilt angles range from 16–51°.

36 MATERIALS SCIENCE↗