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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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31 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on EuCuSeO by Materials Project

EuCuOSe is Parent of FeAs superconductors structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one CuSe sheet oriented in the (0, 0, 1) direction and one EuO sheet oriented in the (0, 0, 1) direction. In the CuSe sheet, Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.49 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Cu1+ atoms. In the EuO sheet, Eu3+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Eu–O bond lengths are 2.30 Å. O2- is bonded to four equivalent Eu3+ atoms to form a mixture of corner and edge-sharing OEu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YCu2Bi2(SeO2)2 by Materials Project

Bi2YO4Cu2Se2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two CuSe sheets oriented in the (0, 0, 1) direction and two Y(BiO2)2 sheets oriented in the (0, 0, 1) direction. In each CuSe sheet, Cu+1.50+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.47 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Cu+1.50+ atoms. In each Y(BiO2)2 sheet, Y3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Y–O bond lengths are 2.40 Å. Bi3+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Bi–O bond lengths are 2.25 Å. O2- is bonded to two equivalent Y3+ and two equivalent Bi3+ atoms to form a mixture of edge and corner-sharing OY2Bi2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaCuSeO by Materials Project

LaCuOSe is Parent of FeAs superconductors structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one CuSe sheet oriented in the (0, 0, 1) direction and one LaO sheet oriented in the (0, 0, 1) direction. In the CuSe sheet, Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.52 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Cu1+ atoms. In the LaO sheet, La3+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All La–O bond lengths are 2.38 Å. O2- is bonded to four equivalent La3+ atoms to form a mixture of corner and edge-sharing OLa4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmCuSeO by Materials Project

SmCuOSe is Parent of FeAs superconductors structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one CuSe sheet oriented in the (0, 0, 1) direction and one SmO sheet oriented in the (0, 0, 1) direction. In the CuSe sheet, Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.52 Å. Se2- is bonded in a 12-coordinate geometry to four equivalent Cu1+ atoms. In the SmO sheet, Sm3+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Sm–O bond lengths are 2.31 Å. O2- is bonded to four equivalent Sm3+ atoms to form a mixture of edge and corner-sharing OSm4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCuSeO by Materials Project

BaOCuSe crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one BaO sheet oriented in the (0, 0, 1) direction and one CuSe sheet oriented in the (0, 0, 1) direction. In the BaO sheet, Ba2+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Ba–O bond lengths are 2.55 Å. O2- is bonded to four equivalent Ba2+ atoms to form a mixture of edge and corner-sharing OBa4 tetrahedra. In the CuSe sheet, Cu2+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.50 Å. Se2- is bonded in a 4-coordinate geometry to four equivalent Cu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe

The entanglement of lattice thermal conductivity, electrical conductivity, and Seebeck coefficient complicates the process of optimizing thermoelectric performance in most thermoelectric materials. Semiconductors with ultralow lattice thermal conductivities and high power factors at the same time are scarce but fundamentally interesting and practically important for energy conversion. In this work, an intrinsic p-type semiconductor TlCuSe that has an intrinsically ultralow thermal conductivity (0.25 W m -1 K -1 ), a high power factor (11.6 μ W cm -1 K -2 ), and a high figure of merit, ZT (1.9) at 643 K is described. The weak chemical bonds, originating from the filled antibonding orbitals p-d* within the edge-sharing CuSe 4 tetrahedra and long Tl-Se bonds in the PbClF-type structure, in conjunction with the large atomic mass of Tl lead to an ultralow sound velocity. Strong anharmonicity, coming from Tl + lone-pair electrons, boosts phonon-phonon scattering rates and further suppresses lattice thermal conductivity. The multiband character of the valence band structure contributing to power factor enhancement benefits from the lone-pair electrons of Tl + as well, which modify the orbital character of the valence bands, and pushes the valence band maximum off the Gamma-point, increasing the band degeneracy. The results provide new insight on the rational design of thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Weak Electron–Phonon Coupling and Enhanced Thermoelectric Performance in n-type PbTe–Cu 2 Se via Dynamic Phase Conversion

This study investigates Ga-doped n-type PbTe thermoelectric materials and the dynamic phase conversion process of the second phases via Cu 2 Se alloying. Introducing Cu 2 Se enhances its electrical transport properties while reducing its lattice thermal conductivity (κlat) via weak electron–phonon coupling. Additionally, Cu 2 Te and CuGa(Te/Se) 2 (tetragonal phase) nanocrystals precipitate during the alloying process, resulting in Te vacancies and interstitial Cu in the PbTe matrix. At room temperature, Te vacancies and interstitial Cu atoms serve as n-type dopants, increasing the carrier concentration and electrical conductivity from ≈1.18 × 10 19 cm –3 and ≈1870 S cm –1 to ≈2.26 × 10 19 cm –3 and ≈3029 S cm –1 , respectively. With increasing temperature, the sample exhibits a dynamic change in Cu 2 Te content and the generation of a new phase of CuGa(Te/Se) 2 (cubic phase), strengthening the phonon scattering and obtaining an ultralow k lat . Pb 0.975 Ga 0.025 Te-3%CuSe exhibits a maximum figure of merit of ≈1.63 at 823 K, making it promising for intermediate-temperature device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Temperature-Dependent Structural Transition in Cu-Intercalated Trigonal CuYbSe 2

Rare-earth delafossites, ARCh 2 ; A = alkali metal, R = rare-earth, Ch = chalcogen which consist of intercalated rare-earth metal dichalcogenides, host frustrated triangular lattices that are fertile ground for exotic phenomena. In most cases, the triangular rare-earth sublattice arises from R-3m (No. 166) structures with three layers of rare-earth metal dichalcogenide octahedra or P6 3 /mmc (No. 194) structures with two such layers, analogous to those found in transition metal dichalcogenides. Substituting the alkali metal with Cu + yields a distinct trigonal crystal symmetry P-3m1 (No. 164) in these structures. This symmetry change alters the coordination environment from ASe 6 octahedra in R-3m AYbSe 2 to CuSe 4 tetrahedra in CuYbSe 2 , resulting in shortened rare-earth to rare-earth separations and significantly reduced interlayer distances. Using X-ray single-crystal diffraction, powder neutron diffraction, resistance, and specific heat measurements, a structural transition slightly below room temperature (258 K) is observed. The low-temperature structure is a lower-symmetry I2/m structure, accompanied by partial Cu-site vacancy ordering. The combination of Cu disorder and the triangular lattice geometry in CuYbSe 2 provides a promising platform for investigating frustrated magnetism and unconventional transport phenomena.

Chemical structure↗
DOE OSTI2021

Modulating the Electron Affinity of Small Bipyridyl Molecules on Single Gold Nanoparticles for Plasmon-Driven Electron Transfer

Developing controlled platforms for plasmon-driven chemistry is of great importance in catalytic reactions at the nanoscale. We report anion radical formation for five bipyridyl complexes of varying degrees of electron affinity utilizing optically fo-cused intraband (594 nm) and interband (532 nm) pump excitation of single gold nanoparticles. The surface-enhanced Raman scattering (SERS) of anion radicals for the five non-resonant adsorbed molecules 2,2’-bipyridine (22BPY), 4,4’-bipyridine (44BPY), trans-1,2-bis(4-pyridyl)ethylene (BPE), 1,2-bis(4-pyridyl)acetylene (BPA), and 1,2-bis(4-pyridyl)ethane (BPEt) were detected using localized surface-plasmon resonance (LSPR) excitation with 785 nm. The electron affinity of the five bipyridyl complexes were determined using electrochemistry. Molecules with low electron affinity experienced high-er instances of radical anion formation under a plasmon-coupled intraband electron transfer excitation (594 nm) whereas molecules with high electron affinity showed a preference for anion radical formation under direct interband electron trans-fer excitation (532 nm). The lowest unoccupied molecular orbital (LUMO) energy levels for low electron affinity surface-bound molecules (22BPY, BPEt) are on average ~0.43 eV higher for high electron affinity surface-bound molecules (BPA, BPE, 44BPY) as calculated using time-dependent density functional theory, elucidating the importance of plasmon coupling to energy levels that facilitate charge transfer pathways. We also show the ability to ‘activate’ high vs low electron affinity single nanoparticles with the choice of pump excitation wavelength. The findings show the complex interplay between molecular electron affinity, orbital overlap with the density of states of the plasmonic metal, and excitation energetics of the pump laser wavelength. Potential applications of this work include enhanced control over molecular scale catalysis, biosensor design, and solar energy capture.

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

Ultrafine Interwoven Dendritic Cu 2 Se/CuFeSe 2 Composites with Enhanced Thermoelectric Performance

As an effort to develop high-performance and stable copper chalcogenide thermoelectrics, several (1-x)Cu 2 Se/(x)CuFeSe 2 composites were successfully synthesized via a one-step solid-state transformation of CuSe 2 template. Uniform ultrafine dendritic structures consisting of interweaving Cu 2 Se and CuFeSe 2 nanofibers were observed in samples with low Fe content (0.05 ≤ x ≤ 0.1). Increasing the Fe content to x = 0.5 led to phase segregation into Cu 2 Se-rich region with embedded CuFeSe 2 fine structures interwoven with CuFeSe 2 -rich region containing Cu 2 Se nanofibers. The formation of such an entwined dendritic structure is believed to arise from the temperature-dependent solubility of CuFeSe 2 in the Cu 2 Se matrix. The dynamic dissolution of CuFeSe 2 into the Cu 2 Se at high temperatures leads to temperature-dependent doping of the Cu 2 Se matrix, enabling drastic enhancements of thermoelectric power factor at high temperatures. As a result, such a strategy is expected to be a powerful tool for properties modulation in thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reversible electrochemical conversion from selenium to cuprous selenide

Using elemental selenium as an electrode, the redox-active Cu 2+ /Cu + ion is reversibly hosted via the sequential conversion reactions of Se → CuSe → Cu 3 Se 2 → Cu 2 Se. Here, the four-electron redox process from Se to Cu 2 Se produces a high initial specific capacity of 1233 mA h g –1 based on the mass of selenium alone or 472 mA h g –1 based on the mass of Cu 2 Se, the fully discharged product.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Stabilized copper selenide thermoelectric materials and methods of fabrication thereof

A thermoelectric composition is provided that includes a nanocomposite comprising a copper selenide (Cu 2 Se) matrix having a plurality of nanoinclusions comprising copper metal selenide (CuMSe 2 ) distributed therein. M may be selected from the group consisting of: indium (In), aluminum (Al), gallium (Ga), antimony (Sb), bismuth (Bi), and combinations thereof. The thermoelectric composition has an average figure of merit (ZT) of greater than or equal to about 1.5 at a temperature of less than or equal to about 850K (about 577° C.). Methods of making such a thermoelectric nanocomposite material by a sequential solid-state transformation of a CuSe 2 precursor are also provided.

Poudeu-Poudeu, Pierre Ferdinand↗