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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ho(BO2)6 by Materials Project

Ho(BO2)6 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Ho is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Ho–O bond distances ranging from 2.34–2.47 Å. There are two inequivalent B sites. In the first B site, B is bonded in a tetrahedral geometry to four O atoms. There are a spread of B–O bond distances ranging from 1.45–1.51 Å. In the second B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.36–1.39 Å. There are four inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Ho and one B atom. In the second O site, O is bonded in a 2-coordinate geometry to one Ho and two B atoms. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one Ho and two B atoms. In the fourth O site, O is bonded in a bent 120 degrees geometry to two B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(PPd)2 by Materials Project

Ho(PdP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent P atoms. All Ho–Pd bond lengths are 3.21 Å. All Ho–P bond lengths are 3.09 Å. Pd is bonded to four equivalent Ho, four equivalent Pd, and four equivalent P atoms to form a mixture of distorted edge, corner, and face-sharing PdHo4P4Pd4 cuboctahedra. All Pd–Pd bond lengths are 2.89 Å. All Pd–P bond lengths are 2.47 Å. P is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Pd, and one P atom. The P–P bond length is 2.19 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(Al2Cu)4 by Materials Project

HoCu4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Ho–Cu bond lengths are 3.36 Å. There are four shorter (3.06 Å) and eight longer (3.19 Å) Ho–Al bond lengths. Cu is bonded in a 12-coordinate geometry to two equivalent Ho, two equivalent Cu, and eight Al atoms. Both Cu–Cu bond lengths are 2.55 Å. There are four shorter (2.56 Å) and four longer (2.68 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Ho, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.68–2.82 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Ho, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(Ge2Rh3)2 by Materials Project

Ho(Rh3Ge2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ho is bonded to six equivalent Rh and six equivalent Ge atoms to form face-sharing HoGe6Rh6 cuboctahedra. All Ho–Rh bond lengths are 3.14 Å. All Ho–Ge bond lengths are 3.12 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.51 Å) and four longer (2.56 Å) Rh–Ge bond lengths. In the second Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Ho and four Ge atoms. There are two shorter (2.47 Å) and two longer (2.56 Å) Rh–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Ho and six Rh atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to nine Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Tailoring Ion Transport in Li 3‐3y Ho 1+y Cl 6‐x Br x via Transition‐Metal Free Structural Planes and Charge Carrier Distribution

Abstract Localized atomistic disorder in halide‐based solid electrolytes (SEs) can be leveraged to boost Li + mobility. In this study, Li + transport in structurally modified Li 3 HoCl 6 , via Br − introduction and Li + deficiency, is explored. The optimized Li 3‐3 y Ho 1+ y Cl 6‐ x Br x achieves an ionic conductivity of 3.8 mS cm −1 at 25 °C, the highest reported for holmium halide materials. 6,7 Li nuclear magnetic resonance and relaxometry investigations unveil enhanced ion dynamics with bromination, attaining a Li + motional rate neighboring 116 MHz. X‐ray diffraction analyses reveal mixed‐anion‐induced phase transitions with disproportionate octahedral expansions and distortions, creating Ho‐free planes with favorable energetics for Li + migration. Bond valence site energy analysis highlights preferred Li + transport pathways, particularly in structural planes devoid of Ho 3+ blocking effects. Molecular dynamics simulations corroborate enhanced Li + diffusion with Br − introduction into Li 3 HoCl 6 . Li‐Ho electrostatic repulsions in the (001) plane presumably drive Li + diffusion into the Ho‐free (002) layer, enabling rapid intraplanar Li + motion and exchange between the 2d and 4h sites. Li 3‐3 y Ho 1+ y Cl 6‐ x Br x also demonstrates good battery cycling stability. These findings offer valuable insights into the intricate correlations between structure and ion transport and will help guide the design of high‐performance fast ion conductors for all‐solid‐state batteries.

Chemistry↗
DOE OSTI2022

Magnetothermal properties of Ho 1-x Dy x Al 2 (x = 0, 0.05, 0.10, 0.15, 0.25 and 0.50) compounds

Magnetic and magnetocaloric properties of H o 1 - x D y x A l 2 compounds with x = 0 , 0.05 , 0.10 , 0.15 , 0.25 and 0.50 , modelled using a Hamiltonian that includes the exchange interactions between Ho-Dy, Ho-Ho and Dy-Dy ions in addition to the crystalline electric field and the Zeeman effects, have been compared with those determined experimentally. In order to reproduce experimentally observed global ferromagnetic ordering temperatures and spin reorientation transition temperatures as x Dy varies, the exchange interactions between Ho-Dy and Ho-Ho were set as free parameters and adjusted to match the experimental results. We demonstrate that heat capacity of polycrystalline materials in non-zero magnetic fields can be satisfactory reproduced by using the average of multiple magnetic field directions with respect to the crystallographic coordinate system, while reasonably good agreement between experimentally determined and theoretically predicted magnetocaloric effects can be achieved considering an average of only three field directions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

New Instrument for Time-Resolved OH and HO 2 Quantification in High-Pressure Laboratory Kinetics Studies

Here, we have constructed a new time-resolved high-pressure fluorescence assay by gas expansion (HP-FAGE) apparatus, optimized for the detection of OH and HO 2 radicals in complex gas-phase reactions. The new instrument fills a gap in the existing experimental toolkit for chemical kinetics by enabling the quantification of two key reactive species with microsecond time resolution from high-pressure sources, which was previously not attainable. The HP-FAGE is interfaced with a flow reactor, designed for pressures up to 100 bar and temperatures up to 1000 K, in which reactions are initiated by laser photolysis of radical precursors at repetition rates of 1–10 Hz. The HP-FAGE samples gas out of the reactor into a miniature FAGE chamber, where OH is detected by resonant laser-induced fluorescence using a time-delayed probe laser pulse. HO 2 is converted to OH via reaction with NO and then detected by OH fluorescence. The novel FAGE design places the probe region very close to the gas expansion, minimizing the transport time of sampled molecules and resulting in time resolution better than 20 μs for both OH and HO 2 . We calibrate the sensitivity of HP-FAGE, validate its performance with measurements of well-known reaction kinetics (OH + CH 4 , OH + OH, OH + HO 2 , and HO 2 + HO 2 ), and discuss prospects for its future use.

calibration↗
DOE OSTI2024

Coercive Fields Exceeding 30 T in the Mixed-Valence Single-Molecule Magnet (Cp iPr5 ) 2 Ho 2 I 3

Mixed-valence dilanthanide complexes of the type (Cp iPr5 ) 2 Ln 2 I 3 (Cp iPr5 = pentaisopropylcyclopentadienyl; Ln = Gd, Tb, Dy) featuring a direct Ln–Ln σ-bonding interaction have been shown to exhibit well-isolated high-spin ground states and, in the case of the Tb and Dy variants, a strong axial magnetic anisotropy that gives rise to a large magnetic coercivity. Here, we report the synthesis and characterization of two new mixed-valence dilanthanide compounds in this series, (Cp iPr5 ) 2 Ln 2 I 3 (1-Ln; Ln = Ho, Er). Both compounds feature a Ln–Ln bonding interaction, the first such interaction in any molecular compounds of Ho or Er. Like the Tb and Dy congeners, both complexes exhibit high-spin ground states arising from strong spin–spin coupling between the lanthanide 4f electrons and a single σ-type lanthanide–lanthanide bonding electron. Beyond these similarities, however, the magnetic properties of the two compounds diverge. In particular, 1-Er does not exhibit observable magnetic blocking or slow magnetic relaxation, while 1-Ho exhibits magnetic blocking below 28 K, which is the highest temperature among Ho-based single-molecule magnets, and a spin reversal barrier of 556(4) cm –1 . Additionally, variable-field magnetization data collected for 1-Ho reveal a coercive field of greater than 32 T below 8 K, more than 6-fold higher than observed for the bulk magnets SmCo 5 and Nd 2 Fe 14 B, and the highest coercive field reported to date for any single-molecule magnet or molecule-based magnetic material. Multiconfigurational calculations, supported by far-infrared magnetospectroscopy data, reveal that the stark differences in magnetic properties of 1-Ho and 1-Er arise from differences in the local magnetic anisotropy of the lanthanide centers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Influence of controlled disorder on the dipolar spin-ice state of Ho-based pyrochlores

Pyrochlore magnets of the form 𝑅 2 ⁢𝐵 2 ⁢O 7 , in which rare-earth ions on the 𝑅 site form a three-dimensional network of corner-sharing tetrahedra, provide a canonical setting for geometrical frustration. Ho-based pyrochlores host a dipolar spin-ice ground state, characterized by Ising moments constrained by the ice rules and elementary excitations analogous to magnetic monopoles. Here, in this work, we examine how controlled chemical disorder influences this state by introducing site mixing on the nonmagnetic 𝐵 site in two compounds. Ho 2⁢ GaSbO 7 contains only Ga 3+ /Sb 5+ charge disorder, whereas Ho 2 ⁢ScSbO 7 exhibits both charge and substantial size disorder arising from the large ionic-radius mismatch between Sc 3+ and Sb 5+ . Although both materials retain the pyrochlore structure, neutron-scattering measurements reveal a reduced correlation length for the 𝑅/𝐵-site cation ordering and enhanced local structural distortions in Ho 2 ⁢ScSbO 7 . Despite these structural differences, bulk thermodynamic measurements and magnetic diffuse scattering demonstrate that both systems exhibit the defining signatures of a dipolar spin-ice state. Low-energy inelastic neutron spectroscopy further uncovers broad magnetic excitations that develop within the dipolar spin-ice regime, a feature absent in pristine Ho pyrochlores and indicative of disorder-induced splitting of the non-Kramers ground-state doublet. Together, these results show that controlled disorder generates tunable transverse-field-driven quantum fluctuations in Ho-based pyrochlores, although the dipolar spin-ice state is remarkably robust to this disorder.

magnetic anisotropy↗
NASA NTRS1992

FAGE measurements of tropospheric HO with measurements and model of interferences

Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August 1987. The observed peak daytime ambient HO concentrations are in the range (2.5 to 8) x 10 exp 6 molecules/cu cm and show small negative offsets due to photochemical interference. Direct measurements of the interference at fixed (O3) give the dependence on ambient (H2O) and on the modulating reagent (isobutane). At ambient (O3) = 30 ppb and 10 torr H2O, with excitation and detection at a total pressure of 4 torr, the net interference is equal to (HO) = -1.3 x 10 exp 6 molecules/cu cm. Production of HO by the reaction of isobutane with O(1D) accounts for the negative interference. Quenching of HO fluorescence by the modulating reagent contributes a smaller positive term to the interference; kinetic measurements of the quenching rate coefficient are reported. The experimental interference results are compared with a detailed kinetic model of HO production, excitation, relaxation, and detection; reasonable agreement is found.

Hard, T. M.↗
NASA NTRS2000

High Energy Directly Pumped Ho:YLF Laser

The most commonly used crystal architecture to produce 2 micrometer laser is co-doping Ho and Tm into a single host crystal. In this method, the stored energy transfer from the Tm (3)F4 to the Ho (5)I7 manifold is not fast enough to warrant high efficiency for short pulse applications. By separating the Ho and the Tm ions and doping the Tm in YALO3 and the Ho in YLF, we were able to directly pump the Ho (5)I7 manifold with 1.94 micrometers. The Ho:YLF laser has produced 33 mJ at 2.062 micrometers with a quantum efficiency of 0.88. The performance of each laser will be presented.

Petros, Mulugeta↗
DOE OSTI2020

Materials Data on Ho(BC)2 by Materials Project

HoB2C2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent B and eight equivalent C atoms. All Ho–B bond lengths are 2.73 Å. All Ho–C bond lengths are 2.67 Å. B is bonded in a distorted trigonal planar geometry to four equivalent Ho and three equivalent C atoms. There is one shorter (1.52 Å) and two longer (1.60 Å) B–C bond length. C is bonded in a 3-coordinate geometry to four equivalent Ho and three equivalent B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(FeGe)2 by Materials Project

HoFe2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent Ge atoms. All Ho–Fe bond lengths are 3.32 Å. All Ho–Ge bond lengths are 3.05 Å. Fe is bonded to four equivalent Ho and four equivalent Ge atoms to form a mixture of edge, corner, and face-sharing FeHo4Ge4 tetrahedra. All Fe–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Fe, and one Ge atom. The Ge–Ge bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(SiRh)2 by Materials Project

HoRh2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Si atoms. All Ho–Rh bond lengths are 3.22 Å. All Ho–Si bond lengths are 3.12 Å. Rh is bonded to four equivalent Ho and four equivalent Si atoms to form a mixture of distorted face, edge, and corner-sharing RhHo4Si4 tetrahedra. All Rh–Si bond lengths are 2.40 Å. Si is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Rh, and one Si atom. The Si–Si bond length is 2.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(SiPd)2 by Materials Project

HoPd2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Si atoms. All Ho–Pd bond lengths are 3.25 Å. All Ho–Si bond lengths are 3.14 Å. Pd is bonded to four equivalent Ho and four equivalent Si atoms to form a mixture of distorted edge, corner, and face-sharing PdHo4Si4 tetrahedra. All Pd–Si bond lengths are 2.47 Å. Si is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Pd, and one Si atom. The Si–Si bond length is 2.31 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(NiGe)2 by Materials Project

HoNi2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Ho–Ni bond lengths are 3.18 Å. All Ho–Ge bond lengths are 3.13 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Ho and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.35 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(CoGe)2 by Materials Project

HoCo2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Ho–Co bond lengths are 3.21 Å. All Ho–Ge bond lengths are 3.08 Å. Co is bonded to four equivalent Ho and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing CoHo4Ge4 tetrahedra. All Co–Ge bond lengths are 2.33 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(CuGe)2 by Materials Project

HoCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Ho–Cu bond lengths are 3.28 Å. All Ho–Ge bond lengths are 3.11 Å. Cu is bonded to four equivalent Ho and four equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing CuHo4Ge4 tetrahedra. All Cu–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.46 Å.

36 MATERIALS SCIENCE↗