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At least 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Pr2InCu2 by Materials Project

Pr2Cu2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Pr is bonded in a 6-coordinate geometry to six equivalent Cu and four equivalent In atoms. There are two shorter (2.99 Å) and four longer (3.02 Å) Pr–Cu bond lengths. All Pr–In bond lengths are 3.47 Å. Cu is bonded in a 9-coordinate geometry to six equivalent Pr, one Cu, and two equivalent In atoms. The Cu–Cu bond length is 2.60 Å. Both Cu–In bond lengths are 3.13 Å. In is bonded to eight equivalent Pr and four equivalent Cu atoms to form a mixture of face and corner-sharing InPr8Cu4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrDyAl4 by Materials Project

DyPrAl4 is Hexagonal Laves-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Dy is bonded in a 12-coordinate geometry to four equivalent Pr and twelve equivalent Al atoms. All Dy–Pr bond lengths are 3.46 Å. All Dy–Al bond lengths are 3.31 Å. Pr is bonded in a 12-coordinate geometry to four equivalent Dy and twelve equivalent Al atoms. All Pr–Al bond lengths are 3.31 Å. Al is bonded to three equivalent Dy, three equivalent Pr, and six equivalent Al atoms to form a mixture of edge, face, and corner-sharing AlPr3Dy3Al6 cuboctahedra. All Al–Al bond lengths are 2.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr3(SiNi3)2 by Materials Project

Pr3(Ni3Si)2 crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Pr is bonded in a 12-coordinate geometry to eight equivalent Ni and four equivalent Si atoms. There are four shorter (2.89 Å) and four longer (2.99 Å) Pr–Ni bond lengths. All Pr–Si bond lengths are 3.18 Å. Ni is bonded in a 12-coordinate geometry to four equivalent Pr, four equivalent Ni, and two equivalent Si atoms. All Ni–Ni bond lengths are 2.58 Å. Both Ni–Si bond lengths are 2.46 Å. Si is bonded to six equivalent Pr and six equivalent Ni atoms to form a mixture of corner and face-sharing SiPr6Ni6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrNiSb by Materials Project

PrNiSb is hexagonal omega structure-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Pr is bonded to six equivalent Ni and six equivalent Sb atoms to form a mixture of edge and face-sharing PrNi6Sb6 cuboctahedra. All Pr–Ni bond lengths are 3.29 Å. All Pr–Sb bond lengths are 3.29 Å. Ni is bonded in a 3-coordinate geometry to six equivalent Pr and three equivalent Sb atoms. All Ni–Sb bond lengths are 2.54 Å. Sb is bonded in a 3-coordinate geometry to six equivalent Pr and three equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrGa2Co3 by Materials Project

PrCo3Ga2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Pr is bonded in a 6-coordinate geometry to twelve equivalent Co and six equivalent Ga atoms. All Pr–Co bond lengths are 3.27 Å. All Pr–Ga bond lengths are 3.09 Å. Co is bonded to four equivalent Pr, four equivalent Co, and four equivalent Ga atoms to form a mixture of distorted corner, edge, and face-sharing CoPr4Ga4Co4 cuboctahedra. All Co–Co bond lengths are 2.68 Å. All Co–Ga bond lengths are 2.43 Å. Ga is bonded in a 9-coordinate geometry to three equivalent Pr and six equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrCo3Ni2 by Materials Project

PrCo3Ni2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Pr is bonded in a 6-coordinate geometry to twelve equivalent Co and six equivalent Ni atoms. All Pr–Co bond lengths are 3.20 Å. All Pr–Ni bond lengths are 2.87 Å. Co is bonded to four equivalent Pr, four equivalent Co, and four equivalent Ni atoms to form a mixture of edge, face, and corner-sharing CoPr4Co4Ni4 cuboctahedra. All Co–Co bond lengths are 2.49 Å. All Co–Ni bond lengths are 2.47 Å. Ni is bonded in a 12-coordinate geometry to three equivalent Pr and six equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrGeIr by Materials Project

PrIrGe crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Pr is bonded in a 9-coordinate geometry to four equivalent Ir and five equivalent Ge atoms. There are a spread of Pr–Ir bond distances ranging from 3.06–3.11 Å. There are a spread of Pr–Ge bond distances ranging from 3.14–3.20 Å. Ir is bonded in a 8-coordinate geometry to four equivalent Pr and four equivalent Ge atoms. There are a spread of Ir–Ge bond distances ranging from 2.54–2.65 Å. Ge is bonded in a 10-coordinate geometry to five equivalent Pr and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr14Au51 by Materials Project

Pr14Au51 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are five inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 11-coordinate geometry to fourteen Au+0.82- atoms. There are a spread of Pr–Au bond distances ranging from 3.13–3.43 Å. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to fourteen Au+0.82- atoms. There are a spread of Pr–Au bond distances ranging from 3.13–3.38 Å. In the third Pr3+ site, Pr3+ is bonded in a 2-coordinate geometry to fourteen Au+0.82- atoms. There are a spread of Pr–Au bond distances ranging from 3.15–3.75 Å. In the fourth Pr3+ site, Pr3+ is bonded in a 1-coordinate geometry to fourteen Au+0.82- atoms. There are a spread of Pr–Au bond distances ranging from 3.01–3.42 Å. In the fifth Pr3+ site, Pr3+ is bonded in a 9-coordinate geometry to fifteen Au+0.82- atoms. There are a spread of Pr–Au bond distances ranging from 3.20–3.44 Å. There are thirteen inequivalent Au+0.82- sites. In the first Au+0.82- site, Au+0.82- is bonded in a 3-coordinate geometry to three equivalent Pr3+ and eight Au+0.82- atoms. There are two shorter (2.87 Å) and six longer (2.99 Å) Au–Au bond lengths. In the second Au+0.82- site, Au+0.82- is bonded in a 11-coordinate geometry to three equivalent Pr3+ and eight Au+0.82- atoms. There are two shorter (2.89 Å) and six longer (2.94 Å) Au–Au bond lengths. In the third Au+0.82- site, Au+0.82- is bonded in a 11-coordinate geometry to four Pr3+ and seven Au+0.82- atoms. There are a spread of Au–Au bond distances ranging from 2.85–3.16 Å. In the fourth Au+0.82- site, Au+0.82- is bonded in a 4-coordinate geometry to four Pr3+ and seven Au+0.82- atoms. There are a spread of Au–Au bond distances ranging from 2.86–3.18 Å. In the fifth Au+0.82- site, Au+0.82- is bonded to four Pr3+ and eight Au+0.82- atoms to form a mixture of edge and face-sharing AuPr4Au8 cuboctahedra. There are a spread of Au–Au bond distances ranging from 2.79–3.00 Å. In the sixth Au+0.82- site, Au+0.82- is bonded in a 12-coordinate geometry to four Pr3+ and eight Au+0.82- atoms. There are a spread of Au–Au bond distances ranging from 2.84–3.17 Å. In the seventh Au+0.82- site, Au+0.82- is bonded to four Pr3+ and eight Au+0.82- atoms to form a mixture of distorted edge and face-sharing AuPr4Au8 cuboctahedra. Both Au–Au bond lengths are 3.00 Å. In the eighth Au+0.82- site, Au+0.82- is bonded in a 12-coordinate geometry to four Pr3+ and eight Au+0.82- atoms. There are one shorter (2.83 Å) and one longer (2.93 Å) Au–Au bond lengths. In the ninth Au+0.82- site, Au+0.82- is bonded in a 11-coordinate geometry to four Pr3+ and seven Au+0.82- atoms. There are a spread of Au–Au bond distances ranging from 2.92–3.08 Å. In the tenth Au+0.82- site, Au+0.82- is bonded in a 11-coordinate geometry to four Pr3+ and seven Au+0.82- atoms. There are one shorter (2.87 Å) and one longer (2.95 Å) Au–Au bond lengths. In the eleventh Au+0.82- site, Au+0.82- is bonded in a 10-coordinate geometry to three equivalent Pr3+ and seven Au+0.82- atoms. In the twelfth Au+0.82- site, Au+0.82- is bonded in a 3-coordinate geometry to three equivalent Pr3+ and seven Au+0.82- atoms. In the thirteenth Au+0.82- site, Au+0.82- is bonded in a 3-coordinate geometry to four Pr3+ and six Au+0.82- atoms. Both Au–Au bond lengths are 2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Elusive Terminal Copper Arylnitrene Intermediates

Abstract We report herein three new modes of reactivity between arylazides N 3 Ar with a bulky copper(I) β‐diketiminate. Addition of N 3 Ar X3 (Ar X3 =2,4,6‐X 3 C 6 H 2 ; X=Cl or Me) to [ i Pr 2 NN]Cu(NCMe) results in triazenido complexes from azide attack on the β‐diketiminato backbone. Reaction of [ i Pr 2 NN]Cu(NCMe) with bulkier azides N 3 Ar leads to terminal nitrenes [ i Pr 2 NN]Cu]=NAr that dimerize via formation of a C−C bond at the arylnitrene p ‐position to give the dicopper(II) diketimide 4 (Ar=2,6‐ i Pr 2 C 6 H 3 ) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4‐Ph‐2,6‐iPr 2 C 6 H 2 ). Importantly, reactivity studies reveal both 4 and 8 to be “masked” forms of the terminal nitrenes [ i Pr 2 NN]Cu=NAr that undergo nitrene group transfer to PMe 3 , t BuNC, and even into a benzylic sp 3 C−H bond of ethylbenzene.

Bakhoda, Abolghasem (Gus)↗
DOE OSTI2019

Highly tunable compact polarization rotator based on silicon on insulator platform

A novel design of an ultra-compact polarization rotator (PR) based on silicon on insulator platform infiltrated with liquid crystal is reported and studied. The anisotropic property of the liquid crystal material leads to a high modal hybridness, which improves the power exchange between the two orthogonal polarized modes. Therefore, tunable and high polarization conversion can be achieved over a short propagation distance. The proposed PR is analyzed by using full-vectorial finite-difference method and full-vectorial finite-difference beam propagation method. At an operating wavelength of 1.55 μm, the PR has a compact device length of 5.4 μm with 14 dB extinction ratio (ER) and 0.15 dB insertion loss. Moreover, the suggested PR offers a relatively broad bandwidth of (1340–1685) nm with an overall ER better than 10 dB. Further, the polarization conversion ratio can be tuned by controlling the rotation angle of the nematic liquid crystal molecules via an external electric field. Furthermore, the fabrication tolerance study shows that the reported PR has high robustness to the fabrication errors.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Antiferromagnetic transitions of osmium-containing rare earth double perovskites Ba{sub 2}LnOsO{sub 6} (Ln=rare earths)

The perovskite-type compounds containing both rare earth and osmium Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm–Lu) have been prepared. Powder X-ray diffraction measurements and Rietveld analysis show that Ln{sup 3+} and Os{sup 5+} ions are structurally ordered at the M site of the perovskite BaMO{sub 3}. Magnetic susceptibility and specific heat measurements show that an antiferromagnetic ordering of Os{sup 5+} ions has been observed for Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm, Eu, Gd, Lu) at 65–71 K. Magnetic ordering of Ln{sup 3+} moments occurs when the temperature is furthermore decreased. - Graphical abstract: The perovskite-type compounds containing both rare earth and osmium Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm–Lu) have been prepared. An antiferromagnetic ordering of Os{sup 5+} ions has been observed for Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm, Eu, Gd, Lu) at 65–71 K. Measurements and analysis of the specific heat for Ba{sub 2}PrOsO{sub 6} show that magnetic ordering of the Pr{sup 3+} moments should have occurred at ∼20 K. Display Omitted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers: Reactant- and stoichiometry-dependent syntheses, effective photocatalytic properties

The systematic study on the reaction variables affecting single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers (CPs) is firstly demonstrated. Five anionic single cyanide-bridged Mo(W)/S/Cu cluster-based CPs {[Pr_4N][WS_4Cu_3(CN)_2]}{sub n} (1), {[Pr_4N][WS_4Cu_4(CN)_3]}{sub n} (2), {[Pr_4N][WOS_3Cu_3(CN)_2]}{sub n} (3), {[Bu_4N][WOS_3Cu_3(CN)_2]}{sub n} (4) and {[Bu_4N][MoOS_3Cu_3(CN)_2]}{sub n} (5) were prepared by varying the molar ratios of the starting materials, and the specific cations, cluster building blocks and central metal atoms in the cluster building blocks. 1 possesses an anionic 3D diamondoid framework constructed from 4-connected T-shaped clusters [WS{sub 4}Cu{sub 3}]{sup +} and single CN{sup −} bridges. 2 is fabricated from 6-connected planar ‘open’ clusters [WS{sub 4}Cu{sub 4}]{sup 2+} and single CN{sup −} bridges, forming an anionic 3D architecture with an “ACS” topology. 3 and 4 exhibit novel anionic 2-D double-layer networks, both constructed from nest-shaped clusters [WOS{sub 3}Cu{sub 3}]{sup +} linked by single CN{sup −} bridges, but containing the different cations [Pr{sub 4}N]{sup +} and [Bu{sub 4}N]{sup +}, respectively. 5 is constructed from nest-shaped clusters [MoOS{sub 3}Cu{sub 3}]{sup +} and single CN{sup −} bridges, with an anionic 3D diamondoid framework. The anionic frameworks of 1-5, all sustained by single CN{sup −} bridges, are non-interpenetrating and exhibit huge potential void volumes. Employing differing molar ratios of the reactants and varying the cluster building blocks resulted in differing single cyanide-bridged Mo(W)/S/Cu cluster-based CPs, while replacing the cation ([Pr{sub 4}N]{sup +} vs. [Bu{sub 4}N]{sup +}) was found to have negligible impact on the nature of the architecture. Unexpectedly, replacement of the central metal atom (W vs. Mo) in the cluster building blocks had a pronounced effect on the framework. Furthermore, the photocatalytic activities of heterothiometallic cluster-based CPs were firstly explored by monitoring the photodegradation of methylene blue (MB) under visible light irradiation, which reveals that 2 exhibits effective photocatalytic properties. - Highlights: • Reaction variables affecting Mo(W)/S/Cu cluster-based CPs is firstly explored. • Replacing central metal atom had a pronounced effect on W/S/Cu cluster-based CPs. • Photocatalytic activities of Mo(W)/S/Cu cluster-based CPs are firstly investigated.

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

Age hardening and creep resistance of cast Al–Cu alloy modified by praseodymium

The effects of praseodymium on age hardening behavior and creep resistance of cast Al–Cu alloy were investigated. The results indicated that praseodymium facilitated the formation of the θ′ precipitates during the age process and improved the hardness of the Al–Cu alloy. Besides, praseodymium resulted in the formation of the Al{sub 11}Pr{sub 3} phase in the grain boundaries and among the dendrites of the modified alloy. Because of the good thermal stability of Al{sub 11}Pr{sub 3} phase, it inhibits grain boundary migration and dislocation movement during the creep process, which contributes to the improvement in the creep resistance of the modified alloy at elevated temperatures. - Highlights: • Pr addition enhances the hardness and creep resistance of the Al–Cu alloy. • Pr addition facilitates the formation of the θ′ precipitates. • Pr addition results in the formation of the Al11Pr3 phase in the Al–Cu alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Blue photons excited highly chromatic red light emitting K3La(PO4)2:Pr3+ phosphors for white light emitting diodes

Highlights: • K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} phosphors were investigated as an alternative for red light. • Highly chromatic red emission was realized upon blue excitation. • The phosphor has high color purity ∼ 97.8% and yield ∼27%. - Abstract: Highly chromatic blue photons excited red emitting K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} (0–1.8 mol%) phosphors were synthesized by solution combustion method. The resulted phosphors showed peanut like morphology and had a monoclinic phase with space group P2{sub 1}/m. The photoluminescence studies disclosed that the phosphor emits red light due to the {sup 1}D{sub 2} → {sup 3}H{sub 4} and {sup 1}D{sub 2} → {sup 3}H{sub 5} transition of the Pr{sup 3+} ions under blue photons excitation. The optimal concentration for the Pr{sup 3+} ions were optimized to be 1.2 mol% after which concentration quenching occurred. Dipole-dipole interaction among the dopant ions was found to be responsible for the concentration quenching. X-ray photoelectron spectroscopy results depicted that Pr was present in the (+3) valance state in the phosphor. The photometric results suggest that the phosphor with a high color purity ∼ 97.8% and enough quantum yield ∼27% could be an eventual choice as the red component for white light emitting diodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Novel red-emitting phosphor Ba3ZrNb4O15:Pr3+: The structure, characteristic photoluminescence property and thermal quenching behaviour investigation

Highlights: • Novel red emitting phosphors BZN:Pr{sup 3+} were successfully synthesized. • Phase purity, morphology and luminescent property of BZN:Pr{sup 3+} were studied. • Different concentration behavior and related mechanism were discussed. • Decay times and the fluorescence dynamics process were investigated. • Temperature sensitive thermal quenching behavior and mechanism was studied. - Abstract: Pr{sup 3+} activated niobate phosphors Ba{sub 3-x}ZrNb{sub 4}O{sub 15}:xPr{sup 3+} were firstly synthesized through high temperature solid-state method. The phase purity, crystal structure, morphology, luminescence property as well as thermal quenching behavior were carefully determined by using X-ray diffractometer, scanned electron microscope, photoluminescence and temperature dependent emission spectra, respectively. The luminescent property showed that Ba{sub 3-x}ZrNb{sub 4}O{sub 15}:xPr{sup 3+} (0.002 ≤ x ≤ 0.03) had dominate excitation around 451 nm and could exhibit red emissions peaking at 608, 618 and 651 nm, attributed to the {sup 1}D{sub 2}-{sup 3}H{sub 4}, {sup 3}P{sub 0}-{sup 3}H{sub 6} and P{sub 0}-{sup 3}F{sub 2} transitions of Pr{sup 3+} ions. The different concentration quenching behaviors were found while the related mechanism was investigated. The room temperature decay times and the related fluorescence dynamics process of Pr{sup 3+} ions in Ba{sub 3}ZrNb{sub 4}O{sub 15} were investigated. In addition, the optimal doping contents, CIE chromaticity coordinates as well as the color purity were determined. At last, the temperature sensitive emission quenching and decay behavior were discussed and the activation energy was calculated based on Arrhenius equation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

The maximum carboxylation rate of Rubisco affects CO2 refixation in temperate broadleaved forest trees

Mesophyll resistance to CO 2 diffusion (rm) and the maximum carboxylation rate of Rubisco (Vcmax) affect photosynthetic rates, and can potentially also influence the percentage of respiratory and photorespiratory CO 2 being refixated (Pr) by mesophyll cells. Here we investigated how various leaf anatomical traits (e.g. leaf mass per area [LMA] and leaf dry matter content [LDMC]) influenced rm in leaves of mature forest trees. We further explored how rm and Vcmax in turn affected Pr, and if these traits varied among species and leaves along a light gradient. Photosynthetic CO 2 response of leaves grown in high-, medium-, and low-light environments was measured, from Pinus sylvestris [Scots pine], Picea abies [Norway spruce], Quercus robur [English oak], and Betula pendula [Silver birch] in southern Sweden. A modified version of the Farquhar-von Caemmerer-Berry model was fitted to the leaf gas exchange data to estimate Vcmax, rm and Pr. We found that of all leaf traits measured, only LMA for Q. robur was significantly higher in leaves from high-light environments. When comparing species, both rm and LMA were significantly higher in the conifers, and rm had a negative correlation with Vcmax. We found that Pr was similar between different species and functional groups, with an average of 73.2% (and SD of ±10.4) across all species. There was a strong, positive correlation between Pr and Vcmax in broadleaves, and we hypothesise that this effect might derive from a higher CO 2 drawdown near Rubisco in leaves with high Vcmax.

59 BASIC BIOLOGICAL SCIENCES↗