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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

New Zintl Phase Yb 10 MgSb 9 with High Thermoelectric Performance

Abstract Yb 10 MgSb 9 is a new Zintl compound (with a composition closer to Yb 10.5 MgSb 9 ) and a promising thermoelectric material first reported in this work. Undoped Yb 10 MgSb 9 has an ultralow thermal conductivity due to crystallographic complexity and exhibits a relatively high peak p‐type Seebeck coefficient and high electrical resistivity. This is consistent with Zintl counting and density functional theory (DFT) calculations that the composition Yb 10.5 MgSb 9 should be a semiconductor. Na is found experimentally to be an effective p‐type dopant potentially due to the replacement of Na + for Yb 2+ , allowing for a significant decrease in electrical resistivity. With doping, a dramatic improvement of electrical conductivity is observed and the glass‐like thermal conductivity remains low, allowing for a significant enhancement of the thermoelectric figure of merit, zT . Doping increases the zT from 0.23 in undoped Yb 10 MgSb 9 to 1.06 in 7 at% Na‐doped Yb 10 MgSb 9 at 873K. This high thermoelectric performance found through Na‐doping places this material amongst the leading p‐type Zintl thermoelectrics, making it a promising candidate for future studies and high‐temperature thermoelectric applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Unravelling competing microscopic interactions at a phase boundary: A single-crystal study of the metastable antiferromagnetic pyrochlore Yb 2 Ge 2 O 7

We report inelastic neutron scattering measurements from our newly synthesized single crystals of the structurally metastable antiferromagnetic pyrochlore Yb 2 Ge 2 O 7 . We determine the four symmetry-allowed nearest-neighbor anisotropic exchange parameters via fits to linear spin wave theory supplemented by fits of the high-temperature specific heat using the numerical linked-cluster expansion method. The exchange parameters so-determined are strongly correlated to the values determined for the g-tensor components, as previously noted for the related Yb pyrochlore Yb 2 Ti 2 O 7 . To address this issue, we directly determined the g-tensor from electron paramagnetic resonance of 1% Yb-doped Lu 2 Ge 2 O 7 , thus enabling an unambiguous determination of the exchange parameters. Our results show that Yb 2 Ge 2 O 7 resides extremely close to the classical phase boundary between an antiferromagnetic Γ 5 phase and a splayed ferromagnet phase. By juxtaposing our results with recent ones on Yb 2 Ti 2 O 7 , our work illustrates that the Yb pyrochlore oxides represent ideal systems for studying quantum magnets in close proximity to classical phase boundaries.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Yb(As2Rh3)2 by Materials Project

Yb(Rh3As2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Yb is bonded to six equivalent Rh and six equivalent As atoms to form face-sharing YbAs6Rh6 cuboctahedra. All Yb–Rh bond lengths are 3.15 Å. All Yb–As bond lengths are 3.05 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five As atoms. There are one shorter (2.55 Å) and four longer (2.59 Å) Rh–As bond lengths. In the second Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Yb and four As atoms. There are two shorter (2.45 Å) and two longer (2.55 Å) Rh–As bond lengths. There are two inequivalent As sites. In the first As site, As is bonded in a 8-coordinate geometry to two equivalent Yb and six Rh atoms. In the second As site, As is bonded in a 9-coordinate geometry to nine Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(GeRu)2 by Materials Project

Yb(RuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Ru and eight equivalent Ge atoms. All Yb–Ru bond lengths are 3.28 Å. All Yb–Ge bond lengths are 3.29 Å. Ru is bonded in a 4-coordinate geometry to four equivalent Yb and four equivalent Ge atoms. All Ru–Ge bond lengths are 2.44 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Ru, and one Ge atom. The Ge–Ge bond length is 2.60 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(ClO4)3 by Materials Project

Yb(ClO4)3 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Yb is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Yb–O bond distances ranging from 2.39–2.54 Å. There are four inequivalent O sites. In the first O site, O is bonded in a water-like geometry to one Yb and one Cl atom. The O–Cl bond length is 1.47 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cl atom. The O–Cl bond length is 1.46 Å. In the third O site, O is bonded in a distorted water-like geometry to one Yb and one Cl atom. The O–Cl bond length is 1.48 Å. In the fourth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.43 Å. Cl is bonded in a tetrahedral geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(GeRh)2 by Materials Project

Yb(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Yb–Rh bond lengths are 3.33 Å. All Yb–Ge bond lengths are 3.22 Å. Rh is bonded to four equivalent Yb and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing RhYb4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.46 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Rh, and one Ge atom. The Ge–Ge bond length is 2.59 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(CoGe)2 by Materials Project

Yb(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Yb–Co bond lengths are 3.24 Å. All Yb–Ge bond lengths are 3.09 Å. Co is bonded to four equivalent Yb and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing CoYb4Ge4 tetrahedra. All Co–Ge bond lengths are 2.33 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Fe2Ge)2 by Materials Project

Yb(Fe2Ge)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Yb is bonded in a 6-coordinate geometry to twelve equivalent Fe and six equivalent Ge atoms. There are four shorter (3.12 Å) and eight longer (3.30 Å) Yb–Fe bond lengths. There are two shorter (2.91 Å) and four longer (2.92 Å) Yb–Ge bond lengths. Fe is bonded in a 3-coordinate geometry to three equivalent Yb and three equivalent Ge atoms. There are two shorter (2.43 Å) and one longer (2.45 Å) Fe–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to three equivalent Yb and six equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Al2Cu)4 by Materials Project

YbCu4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Yb–Cu bond lengths are 3.38 Å. There are four shorter (3.07 Å) and eight longer (3.21 Å) Yb–Al bond lengths. Cu is bonded to two equivalent Yb, two equivalent Cu, and eight Al atoms to form a mixture of distorted edge, corner, and face-sharing CuYb2Al8Cu2 cuboctahedra. Both Cu–Cu bond lengths are 2.56 Å. There are four shorter (2.57 Å) and four longer (2.70 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 Yb, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.83 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Yb, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.74 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Manipulating Cu vacancy in Yb triangular lattice Materials: Investigating the quantum disordered compound CuYbSe 2 and spin glass Cu 2.73 ⁢YbP 2

Yb-based triangular lattice materials have attracted significant attention due to their potential for hosting exotic magnetic quantum states. In this paper, we report the structural, magnetic, and thermodynamic properties of two Yb triangular lattice compounds with vacancy disorder at nonmagnetic Cu sites: CuYbSe 2 and Cu 2.73 ⁢YbP 2 . Single-crystal x-ray diffraction determines notable Cu-site vacancies in both materials. Unlike a single Cu site with 0.5 occupancy in CuYbSe 2 , Cu 2.73 ⁢YbP 2 only presents 27% vacancies on one of three Cu sites. Magnetic susceptibility measurements indicate dominant antiferromagnetic interactions between Yb 3+ ions. The effective magnetic moment is consistent with an effective spin-1/2 state of Yb 3+ . CuYbSe 2 exhibits strong magnetic anisotropy between in-plane and out-of-plane directions with the estimated exchange interactions 𝐽 𝑎 /𝑘 B = 6.48 K and 𝐽 𝑐 /𝑘 B = 2.55 K. No magnetic ordering is observed down to 0.4 K, supporting its quantum disordered ground state and candidacy as a quantum spin liquid. In contrast, Cu 2.73 ⁢YbP 2 shows clear evidence of spin freezing at 4.5 K in both magnetization and heat capacity data, indicating a spin glass state. The field-induced magnetic orders are found in CuYbSe 2 . These results highlight the critical role of structural vacancies in perturbing Yb-based triangular lattices. In conclusion, we demonstrate that while the intrinsic Yb triangular lattices are comparable, the presence of Cu vacancies can fundamentally alter the magnetic ground state—tuning the system between quantum disordered and spin glass behavior.

Frustrated magnetism↗
NASA NTRS2024

Mechanisms of Apatite Formation in Reactions of Yb 2-2x Gd 2x Si 2 O 7 with CMAS

Bulk β-Yb 1.9 Gd 0.1 Si 2 O 7 , β-Yb 1.6 Gd 0.4 Si 2 O 7 , and γ-Yb 1.4 Gd 0.6 Si 2 O 7 , along with baseline γ-Y 2 Si 2 O 7 and β-Yb 2 Si 2 O 7 were investigated in contact with a molten silicate to determine mechanisms of thermochemical degradation. A model 30.67CaO-8.25MgO-12.81AlO 1.5- 48.27SiO 2 silicate composition was deposited on the surfaces of the samples at a loading of ~2 mg/cm 2 . Reactions with the molten silicate resulted in the formation of a silicate apatite layer, which has been shown to reduce further molten silicate infiltration. Additions of gadolinium up to 30 mol% to Yb 2 Si 2 O 7 reduced infiltration up to ~60% compared to baseline Yb 2 Si 2 O 7 , but additional exposure time at temperature resulted in loss of the apatite layer. The results herein indicate that doping with gadolinium disilicate may not be beneficial in the long term degradation of disilicate-based EBCs by molten silicates.

Jamesa L. Stokes↗
DOE OSTI2020

Materials Data on Yb(CuGe)2 by Materials Project

YbCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Yb–Cu bond lengths are 3.27 Å. All Yb–Ge bond lengths are 3.15 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Yb and four equivalent Ge atoms. All Cu–Ge bond lengths are 2.44 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(FeGe)2 by Materials Project

YbFe2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Fe and eight equivalent Ge atoms. All Yb–Fe bond lengths are 3.31 Å. All Yb–Ge bond lengths are 3.05 Å. Fe is bonded to four equivalent Yb and four equivalent Ge atoms to form a mixture of edge, face, and corner-sharing FeYb4Ge4 tetrahedra. All Fe–Ge bond lengths are 2.38 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Fe, and one Ge atom. The Ge–Ge bond length is 2.61 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(GePd)2 by Materials Project

YbPd2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Yb–Pd bond lengths are 3.33 Å. All Yb–Ge bond lengths are 3.31 Å. Pd is bonded in a 4-coordinate geometry to four equivalent Yb and four equivalent Ge atoms. All Pd–Ge bond lengths are 2.52 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Yb, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(ClO4)3 by Materials Project

Yb(ClO4)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Yb is bonded in a 9-coordinate geometry to nine O atoms. There are six shorter (2.44 Å) and three longer (2.51 Å) Yb–O bond lengths. There are three 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 1.43 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cl atom. The O–Cl bond length is 1.46 Å. In the third O site, O is bonded in a bent 150 degrees geometry to one Yb and one Cl atom. The O–Cl bond length is 1.47 Å. Cl is bonded in a tetrahedral geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(AlGa)2 by Materials Project

YbAl2Ga2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Ga and eight equivalent Al atoms. All Yb–Ga bond lengths are 3.25 Å. All Yb–Al bond lengths are 3.46 Å. Ga is bonded in a 9-coordinate geometry to four equivalent Yb, one Ga, and four equivalent Al atoms. The Ga–Ga bond length is 2.46 Å. All Ga–Al bond lengths are 2.60 Å. Al is bonded to four equivalent Yb and four equivalent Ga atoms to form a mixture of distorted face, edge, and corner-sharing AlYb4Ga4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(NiGe)2 by Materials Project

YbNi2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Yb–Ni bond lengths are 3.20 Å. All Yb–Ge bond lengths are 3.13 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Yb 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 Yb, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb by Materials Project

Yb is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Yb is bonded to twelve equivalent Yb atoms to form a mixture of face, edge, and corner-sharing YbYb12 cuboctahedra. There are six shorter (3.85 Å) and six longer (3.89 Å) Yb–Yb bond lengths.

36 MATERIALS SCIENCE↗