Search NASA⌕ Search

SEARCH · Search NASA

Results for “LU”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Comparison of structural and electrical properties of Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} gate dielectrics for α-InGaZnO thin-film transistors

We compared the structural properties and electrical characteristics of high-κ Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} gate dielectrics for amorphous indium-gallium-zinc oxide (α-InGaZnO) thin-film transistor (TFT) applications. The Lu{sub 2}O{sub 3} film has a strong Lu{sub 2}O{sub 3} (400) peak in the X-ray diffraction pattern, while the Lu{sub 2}TiO{sub 5} sample shows a relatively weak Lu{sub 2}TiO{sub 5} (102) peak. Atomic force microscopy reveals that the Lu{sub 2}O{sub 3} dielectric exhibits a rougher surface (about three times) than Lu{sub 2}TiO{sub 5} one. In X-ray photoelectron spectroscopy analysis, we found that the intensity of the O 1s peak corresponding to Lu(OH){sub x} for Lu{sub 2}O{sub 3} film was higher than that of Lu{sub 2}TiO{sub 5} film. Furthermore, compared with the Lu{sub 2}O{sub 3} dielectric, the α-InGaZnO TFT using the Lu{sub 2}TiO{sub 5} gate dielectric exhibited a lower threshold voltage (from 0.43 to 0.25 V), a higher I{sub on}/I{sub off} current ratio (from 3.5 × 10{sup 6} to 1.3 × 10{sup 8}), a smaller subthreshold swing (from 276 to 130 mV/decade), and a larger field-effect mobility (from 14.5 to 24.4 cm{sup 2}/V s). These results are probably due to the incorporation of TiO{sub x} into the Lu{sub 2}O{sub 3} film to form a Lu{sub 2}TiO{sub 5} structure featuring a smooth surface, a low moisture absorption, a high dielectric constant, and a low interface state density at the oxide/channel interface. Furthermore, the stability of Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} α-InGaZnO TFTs was investigated under positive gate-bias stress (PGBS) and negative gate-bias stress (NGBS). The threshold voltage of the TFT performed under NGBS is more degradation than that under PGBS. This behavior may be attributed to the electron charge trapping at the dielectric–channel interface under PGBS, whereas the oxygen vacancies occurred in the InGaZnO under NGBS.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

THE LU ISOTOPIC COMPOSITION OF ACHONDRITES: CLOSING THE CASE FOR ACCELERATED DECAY OF {sup 176}LU

Studies of Lu–Hf isotope systematics in meteorites have produced apparent “ages” that are older than Pb–Pb ages and older than the estimated age of our solar system. One proposed explanation for this discrepancy is that irradiation by cosmic rays caused excitation of {sup 176}Lu to its short-lived isomer that then underwent rapid decay to {sup 176}Hf. This explanation can account for apparent excesses in {sup 176}Hf that correlate with Lu/Hf ratio. Mass balance requires that samples with measurable excess in {sup 176}Hf should also have measurable deficiencies in {sup 176}Lu on the order of 1‰–3‰. To unambiguously test the accelerated decay hypothesis, we have measured the {sup 176}Lu/{sup 175}Lu ratio in terrestrial materials and achondrites to search for evidence of depletion in {sup 176}Lu. To a precision of 0.1‰ terrestrial standards, cumulate and basaltic eucrites and angrites all have the same {sup 176}Lu/{sup 175}Lu ratio. Barring a subsequent mass-dependent fractionation event, these results suggest that the apparent excesses in {sup 176}Hf are not caused by accelerated decay of {sup 176}Lu, and so another hypothesis is required to explain apparently old Lu–Hf ages.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

High-pressure Structural Stability of Multiferroic Hexagonal RMnO3 (R=Y Ho Lu)

Structural changes in RMnO{sub 3} (R = Y, Ho, Lu) under high pressure were examined by synchrotron x-ray diffraction methods at room temperature. Compression occurs more readily in the ab plane than along the c axis. With increased pressure, a pressure-induced hexagonal to orthorhombic phase transition was observed starting at {approx}22 GPa for Lu(Y)MnO{sub 3}. When the pressure is increased to 35 GPa, a small volume fraction of Lu(Y)MnO{sub 3} is converted to the orthorhombic phase and the orthorhombic phase is maintained on pressure release. High-pressure infrared absorption spectroscopy and Mn K-edge near-edge x-ray absorption spectroscopy confirm that the hexagonal P6{sub 3}cm structure is stable below {approx}20 GPa and the environment around the Mn ion is not changed. Shifts in the unoccupied p-band density of states with pressure are observed in the Mn K-edge spectra. A schematic pressure-temperature phase diagram is given for the small ion RMnO{sub 3} system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Correlation consistent basis sets for lanthanides: The atoms La–Lu

Using the 3rd-order Douglas-Kroll-Hess (DKH3) Hamiltonian, all-electron correlation consistent basis sets of double-, triple-, and quadruple-zeta quality have been developed for the lanthanide elements La through Lu. Basis sets designed for the recovery of valence correlation (defined here as 4f5s5p5d6s), cc-pVnZ-DK3, and outer-core correlation (valence + 4s4p4d), cc-pwCVnZ-DK3, are reported (n = D, T, and Q). Systematic convergence of both Hartree-Fock and correlation energies towards their respective complete basis set (CBS) limits are observed. Benchmark calculations of the first three ionization potentials (IPs) of La through Lu are reported at the DKH3 coupled cluster singles and doubles with perturbative triples, CCSD(T), level of theory, including effects of correlation down through the 4s electrons. Spin-orbit coupling is treated at the 2-component HF level. After extrapolation to the CBS limit, the average errors with respect to experiment were just 0.52, 1.14, and 4.24 kcal/mol for the 1st, 2nd, and 3rd IPs, respectively, compared to the average experimental uncertainties of 0.03, 1.78, and 2.65 kcal/mol, respectively. The new basis sets are also used in CCSD(T) benchmark calculations of the equilibrium geometries, atomization energies, and heats of formation for Gd{sub 2}, GdF, and GdF{sub 3}. Except for the equilibrium geometry and harmonic frequency of GdF, which are accurately known from experiment, all other calculated quantities represent significant improvements compared to the existing experimental quantities. With estimated uncertainties of about ±3 kcal/mol, the 0 K atomization energies (298 K heats of formation) are calculated to be (all in kcal/mol): 33.2 (160.1) for Gd{sub 2}, 151.7 (−36.6) for GdF, and 447.1 (−295.2) for GdF{sub 3}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Observation of Vacancies, Faults, and Superstructures in Ln 5 Mo 2 O 12 (Ln = La, Y, and Lu) Compounds with Direct Mo–Mo Bonding

Among oxide compounds with direct metal–metal bonding, the Y 5 Mo 2 O 12 (A 5 B 2 O 12 ) structural family of compounds has a particularly intriguing low-dimensional structure due to the presence of bioctahedral B 2 O 10 dimers arranged in one-dimensional edge-sharing chains along the direction of the metal–metal bonds. Furthermore, these compounds can have a local magnetic moment due to the noninteger oxidation state (+4.5) of the transition metal, in contrast to the conspicuous lack of a local moment that is commonly observed when oxide compounds with direct metal–metal bonding have integer oxidation states resulting from the lifting of orbital degeneracy typically induced by the metal–metal bonding. Although a monoclinic C2/m structure has been previously proposed for Ln 5 Mo 2 O 12 (Ln = La–Lu and Y) members of this family based on prior single crystal diffraction data, it is found that this structural model misses many important structural features. On the basis of synchrotron powder diffraction data, it is shown in this paper that the C2/m monoclinic unit cell represents a superstructure relative to a previously unrecognized orthorhombic Immm subcell and that the superstructure derives from the ordering of interchangeable Mo 2 O 10 and LaO 6 building blocks. The superstructure for this reason is typically highly faulted, as evidenced by the increased breadth of superstructure diffraction peaks associated with a coherence length of 1–2 nm in the c* direction. Finally, it is shown that oxygen vacancies can occur when Ln = La, producing an oxygen deficient stoichiometry of La 5 Mo 2 O 11.55 and an approximately 10-fold reduction in the number of unpaired electrons due to the reduction of the average Mo valence from +4.5 to +4.05, a result confirmed by magnetic susceptibility measurements. Finally, this represents the first observation of oxygen vacancies in this family of compounds and provides an important means of continuously tuning the magnetic interactions within the one-dimensional octahedral chains of this system.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High temperature hydrothermal synthesis of rare-earth titanates: synthesis and structure of RE 5 Ti 4 O 15 (OH) (RE = La, Er), Sm 3 TiO 5 (OH) 3 , RE 5 Ti 2 O 11 (OH) (RE = Tm–Lu) and Ce 2 Ti 4 O 11

Reactions of rare-earth oxides with TiO 2 were performed in high temperature (650–700 °C) hydrothermal fluids. Two different mineralizer fluids were examined, 20 M KOH and 30 M CsF, and their respective products analyzed. When concentrated KOH fluids were used, single crystals of a variety of new OH - containing species were isolated and structurally characterized: RE 5 Ti 4 O 15 (OH) (RE = La, Er) I, Sm 3 TiO 5 (OH) 3 II and RE 5 Ti 2 O 11 (OH) (RE = Tm–Lu) III. La 5 Ti 4 O 15 (OH) I crystallizes in the orthorhombic space group Pnnm with unit cell dimensions of a = 30.5152(12) Å, b = 5.5832(2) Å, c = 7.7590(3) Å and V = 1321.92(9) Å 3 , Z = 4. Sm 3 TiO 5 (OH) 3 II crystallizes in the monoclinic space group P21/m with unit cell parameters of a = 5.6066(2) Å, b = 10.4622(4) Å, c = 6.1258(2) Å and β = 104.7390(10)°, V = 347.50(2) Å3, Z = 2. Lu5Ti2O11(OH) III crystallizes in the monoclinic space group C2/m with unit cell dimensions of a = 12.1252(9) Å, b = 5.8243(4) Å, c = 7.0407(5) Å, β = 106.939(3)° and V = 475.65(6) Å3, Z = 2. When concentrated fluoride solutions are used, mostly RE 2 Ti 2 O 7 type compounds were isolated in either cubic or monoclinic phases. In the case of cerium, Ce2Ti4O11IV was isolated that crystallizes in the monoclinic space group C2/c with unit cell parameters of a = 13.6875(7) Å, b = 5.0955(3) Å, c = 12.8592(7) Å, β = 108.964(2)° and V = 848.18(8) Å 3 , Z = 4. The synthesis, structural characterization, and supporting characterization are reported for all compounds. The work highlights the complementary nature of hydroxide and fluoride fluids in studying the reactivity of refractory oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu by Materials Project

Lu is alpha Samarium structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are seven inequivalent Lu sites. In the first Lu site, Lu is bonded to twelve Lu atoms to form LuLu12 cuboctahedra that share corners with eighteen LuLu16 cuboctahedra, edges with eighteen LuLu12 cuboctahedra, and faces with twenty LuLu12 cuboctahedra. There are six shorter (3.44 Å) and six longer (3.49 Å) Lu–Lu bond lengths. In the second Lu site, Lu is bonded to twelve Lu atoms to form a mixture of edge, corner, and face-sharing LuLu12 cuboctahedra. There are a spread of Lu–Lu bond distances ranging from 3.42–3.49 Å. In the third Lu site, Lu is bonded to twelve Lu atoms to form a mixture of edge, corner, and face-sharing LuLu12 cuboctahedra. All Lu–Lu bond lengths are 3.49 Å. In the fourth Lu site, Lu is bonded to twelve Lu atoms to form LuLu12 cuboctahedra that share corners with fifteen LuLu12 cuboctahedra, edges with twenty-one LuLu16 cuboctahedra, and faces with nineteen LuLu12 cuboctahedra. There are a spread of Lu–Lu bond distances ranging from 3.42–3.49 Å. In the fifth Lu site, Lu is bonded to twelve Lu atoms to form a mixture of edge, corner, and face-sharing LuLu12 cuboctahedra. There are three shorter (3.44 Å) and six longer (3.49 Å) Lu–Lu bond lengths. In the sixth Lu site, Lu is bonded to twelve Lu atoms to form a mixture of edge, corner, and face-sharing LuLu12 cuboctahedra. There are three shorter (3.42 Å) and six longer (3.49 Å) Lu–Lu bond lengths. In the seventh Lu site, Lu is bonded to sixteen Lu atoms to form LuLu16 cuboctahedra that share corners with twenty-five LuLu12 cuboctahedra, edges with twenty-one LuLu16 cuboctahedra, and faces with thirty-five LuLu16 cuboctahedra. There are a spread of Lu–Lu bond distances ranging from 3.49–6.97 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(Al5Re)2 by Materials Project

LuRe2Al10 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Lu sites. In the first Lu site, Lu is bonded in a 10-coordinate geometry to four Re and sixteen Al atoms. There are two shorter (3.39 Å) and two longer (3.51 Å) Lu–Re bond lengths. There are a spread of Lu–Al bond distances ranging from 3.04–3.50 Å. In the second Lu site, Lu is bonded in a 4-coordinate geometry to fourteen Al atoms. There are a spread of Lu–Al bond distances ranging from 3.04–3.28 Å. There are two inequivalent Re sites. In the first Re site, Re is bonded in a 10-coordinate geometry to one Lu and ten Al atoms. There are a spread of Re–Al bond distances ranging from 2.55–2.79 Å. In the second Re site, Re is bonded in a 10-coordinate geometry to two equivalent Lu and ten Al atoms. There are a spread of Re–Al bond distances ranging from 2.57–2.74 Å. There are twelve inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Lu, two equivalent Re, and four Al atoms. There are two shorter (2.72 Å) and two longer (3.08 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 12-coordinate geometry to one Lu, two equivalent Re, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.66–3.14 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Lu, two equivalent Re, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.67–3.04 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to one Lu, two equivalent Re, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.80–3.11 Å. In the fifth Al site, Al is bonded in a 12-coordinate geometry to two Lu, two equivalent Re, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.63–3.03 Å. In the sixth Al site, Al is bonded in a 2-coordinate geometry to two Lu, two equivalent Re, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.66–2.97 Å. In the seventh Al site, Al is bonded in a 2-coordinate geometry to one Lu, two equivalent Re, and eight Al atoms. There are two shorter (2.75 Å) and two longer (3.06 Å) Al–Al bond lengths. In the eighth Al site, Al is bonded in a 2-coordinate geometry to one Lu, two equivalent Re, and nine Al atoms. There are two shorter (2.68 Å) and two longer (2.89 Å) Al–Al bond lengths. In the ninth Al site, Al is bonded in a 2-coordinate geometry to two Lu, two equivalent Re, and eight Al atoms. The Al–Al bond length is 2.71 Å. In the tenth Al site, Al is bonded in a 11-coordinate geometry to one Lu, two equivalent Re, and eight Al atoms. Both Al–Al bond lengths are 2.97 Å. In the eleventh Al site, Al is bonded in a distorted linear geometry to two equivalent Lu, two Re, and four Al atoms. In the twelfth Al site, Al is bonded in a 2-coordinate geometry to one Lu, two Re, and four Al atoms.

36 MATERIALS SCIENCE↗