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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Site preference, magnetism and lattice vibrations of intermetallics Lu₂Fe 17–x T x (T=Cr, Mn, Ru)

We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth intermetallics Lu₂Fe 17–x T x (T=Cr, Mn, Ru). The calculated preferential occupation site of ternary element T is found to be the 4f site. The order of site preference is given as 4f, 12k, 12j and 6g for Lu₂Fe 17–x T x . The calculated lattice parameters are corresponding to the experimental results. We have calculated the magnetic moments of Lu₂Fe 17–x T x compounds. Results show that the calculated total magnetic moment of Lu₂Fe₁₇ compound is M=37.34 μ B /f.u. In addition, the total and partial phonon densities of states are evaluated first for these complicated structures. - Graphical abstract: The vibrational modes are mostly excited by Fe atoms, Lu contributes to the lower frequencies modes, and the contribution of Ru atoms is the same as Fe atoms. Highlights: • There are no reports on lattice vibrations of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The phase stability and site preference are evaluated first for the complex structures of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The lattice inversion method to obtain the interatomic pair potential is the unique one.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Oxygen miscibility gap and spin glass formation in the pyrochlore Lu{sub 2}Mo{sub 2}O{sub 7}

Rare earth (R) molybdate pyrochlores, R{sub 2}Mo{sub 2}O{sub 7}, are of interest as frustrated magnets. Polycrystalline samples of Lu{sub 2}Mo{sub 2}O{sub 7−x} prepared at 1600 °C display a coexistence of cubic pyrochlore phases. Rietveld fits to powder neutron diffraction data and chemical analyses show that the miscibility gap is between a stoichiometric x=0 and an oxygen-deficient x≈0.4 phase. Lu{sub 2}Mo{sub 2}O{sub 7} behaves as a spin glass material, with a divergence of field cooled and zero field cooled DC magnetic susceptibilities at a spin freezing temperature T{sub f}=16 K, that varies with frequency in AC measurements following a Vogel–Fulcher law. Lu{sub 2}Mo{sub 2}O{sub 6.6} is more highly frustrated spin glass and has T{sub f}=20 K. - Graphical abstract: The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system exhibits a miscibility gap between coexisting pyrochlore phases at 1600 °C. Neutron powder diffraction refinement and chemical analysis shows that the gap separates stoichiometric x=0 and oxygen-deficient x≈0.4 phases. Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content. - Highlights: • The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system has a miscibility gap between coexisting pyrochlore phases at 1600 °C. • Neutron powder diffraction shows that the gap separates x=0 and oxygen-deficient x≈0.4 phases. • Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Large-scale synthesis of Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres and their photoluminescence properties

Graphical abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. Display Omitted Highlights: ► Lu{sub 2}O{sub 3}:Ln{sup 3+} microspheres were prepared by a precipitation followed by a calcination process. ► Lu{sub 2}O{sub 3}:Eu{sup 3+}/Tb{sup 3+} samples exhibit respective red or green emissions. ► Lu{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}/Tm{sup 3+}/Ho{sup 3+} exhibit emissions of green, blue, yellow-green, respectively. ► These finding may find potential applications in bioanalysis and field emission displays. -- Abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. Upon ultraviolet and low-voltage electron beams excitation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+} and Tb{sup 3+}) samples exhibit respective bright red (Eu{sup 3+}, {sup 5}D{sub 0} → {sup 7}F{sub 2}) and green (Tb{sup 3+}, {sup 5}D{sub 4} → {sup 7}F{sub 5}) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) exhibit characteristic up-conversion (UC) emissions of green (Er{sup 3+}, {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} → {sup 4}I{sub 15/2}), blue (Tm{sup 3+}, {sup 1}G{sub 4} → {sup 3}H{sub 6}) and yellow-green (Ho{sup 3+}, {sup 5}F{sub 4}, {sup 5}S{sub 2} → {sup 5}I{sub 8}), respectively. These finding may find potential applications in bioanalysis, optoelectronic and nanoscale devices, field emission displays, and so on.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Measurements and computational analysis of the natural decay of 176 Lu

Background: Mainly because of its long half-life and despite its scientific relevance, spectroscopic measurements of 176 Lu forbidden β decays are very limited and lack formulation of shape factors. A direct precise measurement of its Q value is also presently unreported. In addition, the description of forbidden decays provides interesting challenges for nuclear theory. The comparison of precise experimental results with theoretical calculations for these decays can help to test underlying models and can aid the interpretation of data from other experiments. Purpose: Perform the first precision measurements of 176 Lu β-decay spectra and attempt the observation of its electron capture decays, as well as perform the first precision direct measurement of the 176 Lu β-decay Q value. Compare the shape of the precisely determined experimental β spectra to theoretical calculations, and compare the end point energy to that obtained from an independent Q value measurement. Method: Here, the 176 Lu β-decay spectra measurements and the search for electron capture decays were performed with an experimental setup that employed lutetium-containing scintillator crystals and a NaI(Tl) spectrometer for coincidence counting. The β decay Q value was determined via high-precision Penning trap mass spectrometry (PTMS) with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The β-spectrum calculations were performed within the Fermi theory formalism with nuclear structure effects calculated using a shell model approach. Results: Both β transitions of 176 Lu were experimentally observed and corresponding shape factors formulated in their entire energy ranges. The search for electron capture decay branches led to an experimental upper limit of 6.3×10 –6 relative to its β decays. The 176 Lu β-decay and electron capture Q values were measured using PTMS to be 1193.0(6) and 108.9(8) keV, respectively. This enabled precise β end point energies of 596.2(6) and 195.3(6) keV to be determined for the primary and secondary β decays, respectively. The conserved vector current hypothesis was applied to calculate the relativistic vector matrix elements. The β-spectrum shape was shown to significantly depend on the Coulomb displacement energy and on the value of the axial vector coupling constant gA, which was extracted according to different assumptions. Conclusion: The implemented self-scintillation method has provided unmatched observations of 176 Lu, independently validated by the first direct measurements of its β-decay Q value by Penning trap mass spectrometry. Theoretical study of the main β transition led to the extraction of very different effective gA and log10f values, showing that a high-precision description of this transition would require a realistic nuclear structure with nucleus deformation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Lu-Hf and Sm-Nd geochronological constraints on the influence of subduction metamorphism in controlling the Hf-Nd terrestrial array: Evidence from the world’s orogenic belts

To create a better understanding of the influence of subduction metamorphism on the Hf-Nd terrestrial array, this study examines all of the available Lu-Hf and Sm-Nd garnet isochron ages from the world’s orogenic eclogites and amphi bolites. The garnet isochron y-intercept values provide a record of each sample’s epsilon Hf ( ε Hf) and Nd ( ε Nd) at the age recorded by the isochron, which in the case of most orogenic eclogites and amphibolites is the time of prograde metamorphism during subduction. It is further possible to assess the extent to which each sample’s Lu-Hf and Sm-Nd isotope systematics have remained undisturbed since the date recorded by the isochron by comparison of the bulk-rock isotope systematics with the isochron initial value. This approach provides a means of understanding the Lu-Hf and Sm-Nd systematics of post-subduction metamorphic oceanic crust. On a global scale, the coupled Lu-Hf and Sm-Nd isotope systematics of this crust closely align with the Hf-Nd terrestrial array and have average 176 Lu/ 177 Hf and 147 Sm/ 144 Nd ratios within error of the chondritic uniform reservoir values. This is an important finding because it suggests that a reservoir of deeply subducted oceanic crust, possibly residing at the core-mantle boundary, is unlikely to be significantly fractionated from the Hf-Nd terrestrial array. In contrast to the samples of subduction-metamorphosed oceanic crust, metamorphic rocks with a continental crustal protolith demonstrate garnet isochron initial values and bulk-rock Lu-Hf and Sm-Nd isotope systematics indicating significant decoupling from the Hf-Nd terrestrial array. However, because this material is not readily subducted, this strongly decoupled signature is unlikely to be transferred into deep Earth. Mixing calculations aimed at developing a clearer understanding of what factors control decoupling of a sample’s Lu-Hf and Sm-Nd systematics from the Hf-Nd terrestrial array highlight the complexity of mass-transfer regimes operating in the subduction environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on Lu(BC)2 by Materials Project

Lu(BC)2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to eight equivalent B and eight equivalent C atoms. All Lu–B bond lengths are 2.69 Å. All Lu–C bond lengths are 2.63 Å. B is bonded in a distorted trigonal planar geometry to four equivalent Lu and three equivalent C atoms. There is one shorter (1.52 Å) and two longer (1.59 Å) B–C bond length. C is bonded in a 3-coordinate geometry to four equivalent Lu and three equivalent B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(Al2Fe)4 by Materials Project

LuFe4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Lu is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Al atoms. All Lu–Fe bond lengths are 3.31 Å. There are four shorter (2.94 Å) and eight longer (3.14 Å) Lu–Al bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent Lu, two equivalent Fe, and eight Al atoms. Both Fe–Fe bond lengths are 2.51 Å. There are four shorter (2.51 Å) and four longer (2.62 Å) Fe–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Lu, four equivalent Fe, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.71–2.80 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Lu, four equivalent Fe, and six Al atoms. Both Al–Al bond lengths are 2.68 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(FeB)2 by Materials Project

Lu(FeB)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent B atoms. All Lu–Fe bond lengths are 2.89 Å. All Lu–B bond lengths are 2.66 Å. Fe is bonded to four equivalent Lu and four equivalent B atoms to form a mixture of distorted face, edge, and corner-sharing FeLu4B4 tetrahedra. All Fe–B bond lengths are 2.16 Å. B is bonded in a 9-coordinate geometry to four equivalent Lu, four equivalent Fe, and one B atom. The B–B bond length is 2.05 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(NiGe)2 by Materials Project

Lu(NiGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Lu–Ni bond lengths are 3.16 Å. All Lu–Ge bond lengths are 3.10 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Lu and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.34 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Lu, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Materials Data on Lu(ClO4)3 by Materials Project

Lu(ClO4)3 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Lu is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Lu–O bond distances ranging from 2.33–2.41 Å. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the second O site, O is bonded in a water-like geometry to one Lu and one Cl atom. The O–Cl bond length is 1.48 Å. In the third O site, O is bonded in a bent 150 degrees geometry to one Lu and one Cl atom. The O–Cl bond length is 1.47 Å. In the fourth O site, O is bonded in a water-like geometry to one Lu and one Cl atom. The O–Cl bond length is 1.48 Å. Cl is bonded in a tetrahedral geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(CoGe)2 by Materials Project

Lu(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Lu–Co bond lengths are 3.19 Å. All Lu–Ge bond lengths are 3.05 Å. Co is bonded to four equivalent Lu and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing CoLu4Ge4 tetrahedra. All Co–Ge bond lengths are 2.32 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Lu, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.53 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(BRh)4 by Materials Project

Lu(RhB)4 crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are a spread of Lu–Rh bond distances ranging from 2.90–3.25 Å. There are a spread of Lu–B bond distances ranging from 2.95–3.25 Å. Rh is bonded in a 5-coordinate geometry to three equivalent Lu and five equivalent B atoms. There are a spread of Rh–B bond distances ranging from 2.18–2.26 Å. B is bonded in a 6-coordinate geometry to three equivalent Lu, five equivalent Rh, and one B atom. The B–B bond length is 1.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(Mg4Al3)4 by Materials Project

Lu(Mg4Al3)4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to three equivalent Mg, one Lu, and six equivalent Al atoms. All Mg–Mg bond lengths are 3.03 Å. The Mg–Lu bond length is 3.24 Å. All Mg–Al bond lengths are 3.14 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are two shorter (3.11 Å) and four longer (3.16 Å) Mg–Mg bond lengths. There are a spread of Mg–Al bond distances ranging from 2.87–3.17 Å. Lu is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Lu–Al bond lengths are 3.21 Å. Al is bonded in a 11-coordinate geometry to seven Mg, one Lu, and three equivalent Al atoms. There are one shorter (2.69 Å) and two longer (2.77 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(BC)2 by Materials Project

Lu(BC)2 crystallizes in the tetragonal P4_2/mmc space group. The structure is three-dimensional. Lu is bonded in a 8-coordinate geometry to eight equivalent B and eight equivalent C atoms. All Lu–B bond lengths are 2.69 Å. All Lu–C bond lengths are 2.66 Å. B is bonded in a 2-coordinate geometry to four equivalent Lu and two equivalent C atoms. Both B–C bond lengths are 1.60 Å. C is bonded in a 2-coordinate geometry to four equivalent Lu, two equivalent B, and one C atom. The C–C bond length is 1.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(FeSn)6 by Materials Project

LuFe6Sn6 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Lu is bonded to twelve equivalent Fe and eight Sn atoms to form distorted LuFe12Sn8 hexagonal bipyramids that share faces with twenty-four equivalent FeLu2Fe4Sn6 cuboctahedra and faces with six equivalent LuFe12Sn8 hexagonal bipyramids. All Lu–Fe bond lengths are 3.48 Å. There are two shorter (3.01 Å) and six longer (3.12 Å) Lu–Sn bond lengths. Fe is bonded to two equivalent Lu, four equivalent Fe, and six Sn atoms to form distorted FeLu2Fe4Sn6 cuboctahedra that share corners with fourteen equivalent FeLu2Fe4Sn6 cuboctahedra, edges with seven equivalent FeLu2Fe4Sn6 cuboctahedra, faces with nine equivalent FeLu2Fe4Sn6 cuboctahedra, and faces with four equivalent LuFe12Sn8 hexagonal bipyramids. All Fe–Fe bond lengths are 2.71 Å. There are a spread of Fe–Sn bond distances ranging from 2.69–2.83 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 12-coordinate geometry to three equivalent Lu and six equivalent Fe atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Fe atoms. In the third Sn site, Sn is bonded in a 8-coordinate geometry to one Lu, six equivalent Fe, and one Sn atom. The Sn–Sn bond length is 2.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(BRh)4 by Materials Project

Lu(RhB)4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Lu is bonded in a 12-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are four shorter (2.94 Å) and eight longer (3.17 Å) Lu–Rh bond lengths. There are eight shorter (3.02 Å) and four longer (3.14 Å) Lu–B bond lengths. Rh is bonded in a 5-coordinate geometry to three equivalent Lu and five equivalent B atoms. There are four shorter (2.21 Å) and one longer (2.24 Å) Rh–B bond lengths. B is bonded in a 6-coordinate geometry to three equivalent Lu, five equivalent Rh, and one B atom. The B–B bond length is 1.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(P2Rh3)2 by Materials Project

Lu(Rh3P2)2 crystallizes in the trigonal P3 space group. The structure is three-dimensional. Lu is bonded to six equivalent Rh and six equivalent P atoms to form face-sharing LuP6Rh6 cuboctahedra. There are three shorter (3.00 Å) and three longer (3.01 Å) Lu–Rh bond lengths. All Lu–P bond lengths are 2.95 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Rh–P bond distances ranging from 2.42–2.52 Å. In the second Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Lu and four P atoms. There are a spread of Rh–P bond distances ranging from 2.32–2.51 Å. There are two inequivalent P sites. In the first P site, P is bonded in a 9-coordinate geometry to nine Rh atoms. In the second P site, P is bonded in a 8-coordinate geometry to two equivalent Lu and six Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Materials Data on Lu(Fe2Ge)2 by Materials Project

LuFe4Ge2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Lu is bonded in a 6-coordinate geometry to twelve Fe and six equivalent Ge atoms. There are a spread of Lu–Fe bond distances ranging from 3.08–3.29 Å. There are two shorter (2.89 Å) and four longer (2.92 Å) Lu–Ge bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 3-coordinate geometry to three equivalent Lu and three equivalent Ge atoms. There are one shorter (2.43 Å) and two longer (2.46 Å) Fe–Ge bond lengths. In the second Fe site, Fe is bonded in a 3-coordinate geometry to three equivalent Lu and three equivalent Ge atoms. All Fe–Ge bond lengths are 2.41 Å. Ge is bonded in a 9-coordinate geometry to three equivalent Lu and six Fe atoms.

36 MATERIALS SCIENCE↗