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At least 145 records · Page 8
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DOE OSTI2020

Materials Data on Yb(TmS2)2 by Materials Project

Yb(TmS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Yb2+ is bonded to seven S2- atoms to form distorted YbS7 pentagonal bipyramids that share corners with eight TmS6 octahedra, edges with five TmS6 octahedra, edges with two equivalent YbS7 pentagonal bipyramids, and faces with two equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 14–67°. There are a spread of Yb–S bond distances ranging from 2.86–2.98 Å. There are two inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with six TmS6 octahedra, and an edgeedge with one YbS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.68–2.78 Å. In the second Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with four TmS6 octahedra, and edges with four equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.67–2.75 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Yb2+ and three Tm3+ atoms to form a mixture of distorted edge and corner-sharing SYb2Tm3 trigonal bipyramids. In the second S2- site, S2- is bonded to two equivalent Yb2+ and three Tm3+ atoms to form SYb2Tm3 square pyramids that share corners with two equivalent SYb3Tm2 square pyramids, corners with two equivalent SYb2Tm3 trigonal bipyramids, edges with five SYb2Tm3 square pyramids, and edges with three equivalent SYb2Tm3 trigonal bipyramids. In the third S2- site, S2- is bonded to three equivalent Yb2+ and two equivalent Tm3+ atoms to form a mixture of distorted edge and corner-sharing SYb3Tm2 square pyramids. In the fourth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Tm3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(CuS)3 by Materials Project

Yb(CuS)3 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Yb3+ is bonded to six equivalent S2- atoms to form YbS6 octahedra that share corners with twelve equivalent CuS4 tetrahedra, edges with three equivalent YbS6 octahedra, and edges with six equivalent CuS4 tetrahedra. All Yb–S bond lengths are 2.76 Å. Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with four equivalent YbS6 octahedra, corners with six equivalent CuS4 tetrahedra, edges with two equivalent YbS6 octahedra, and edges with three equivalent CuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–53°. There are a spread of Cu–S bond distances ranging from 2.27–2.41 Å. S2- is bonded in a 6-coordinate geometry to two equivalent Yb3+ and four equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(GaS2)2 by Materials Project

Yb(GaS2)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Yb2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (2.97 Å) and four longer (3.03 Å) Yb–S bond lengths. Ga3+ is bonded to four S2- atoms to form edge-sharing GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.28–2.34 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Yb2+ and two equivalent Ga3+ atoms. In the second S2- site, S2- is bonded to two equivalent Yb2+ and two equivalent Ga3+ atoms to form a mixture of distorted edge and corner-sharing SYb2Ga2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(InS2)2 by Materials Project

Yb(InS2)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Yb2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (2.99 Å) and four longer (3.11 Å) Yb–S bond lengths. In3+ is bonded to four S2- atoms to form edge-sharing InS4 tetrahedra. There are a spread of In–S bond distances ranging from 2.47–2.57 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Yb2+ and two equivalent In3+ atoms. In the second S2- site, S2- is bonded to two equivalent Yb2+ and two equivalent In3+ atoms to form a mixture of distorted corner and edge-sharing SYb2In2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Mo3Se4)2 by Materials Project

Yb(Mo3Se4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Yb3+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.87 Å) and six longer (3.17 Å) Yb–Se bond lengths. Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.53–2.77 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Yb3+ and three equivalent Mo+2.17+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Yb3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(BiS2)2 by Materials Project

Yb(BiS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Yb2+ is bonded to seven S2- atoms to form distorted YbS7 pentagonal bipyramids that share corners with four equivalent BiS6 octahedra, corners with four equivalent BiS7 pentagonal bipyramids, edges with three equivalent BiS6 octahedra, edges with three equivalent BiS7 pentagonal bipyramids, a faceface with one BiS7 pentagonal bipyramid, and faces with two equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 5–71°. There are a spread of Yb–S bond distances ranging from 2.90–3.03 Å. There are two inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six S2- atoms to form BiS6 octahedra that share corners with three equivalent BiS7 pentagonal bipyramids, corners with four equivalent YbS7 pentagonal bipyramids, edges with four equivalent BiS6 octahedra, edges with two equivalent BiS7 pentagonal bipyramids, and edges with three equivalent YbS7 pentagonal bipyramids. There are a spread of Bi–S bond distances ranging from 2.68–3.08 Å. In the second Bi3+ site, Bi3+ is bonded to seven S2- atoms to form distorted BiS7 pentagonal bipyramids that share corners with three equivalent BiS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with two equivalent BiS6 octahedra, edges with three equivalent YbS7 pentagonal bipyramids, edges with four equivalent BiS7 pentagonal bipyramids, and a faceface with one YbS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 9–49°. There are a spread of Bi–S bond distances ranging from 2.81–3.14 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Yb2+ and four Bi3+ atoms to form distorted SYb2Bi4 octahedra that share corners with four equivalent SYb2Bi3 square pyramids, corners with three equivalent SYbBi3 trigonal pyramids, edges with four equivalent SYb2Bi4 octahedra, edges with three equivalent SYbBi3 trigonal pyramids, and a faceface with one SYb2Bi3 square pyramid. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Yb2+ and three Bi3+ atoms. In the third S2- site, S2- is bonded to two equivalent Yb2+ and three equivalent Bi3+ atoms to form distorted SYb2Bi3 square pyramids that share corners with four equivalent SYb2Bi4 octahedra, corners with five equivalent SYbBi3 trigonal pyramids, edges with four equivalent SYb2Bi3 square pyramids, and a faceface with one SYb2Bi4 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. In the fourth S2- site, S2- is bonded to one Yb2+ and three Bi3+ atoms to form distorted SYbBi3 trigonal pyramids that share corners with three equivalent SYb2Bi4 octahedra, corners with five equivalent SYb2Bi3 square pyramids, corners with two equivalent SYbBi3 trigonal pyramids, and edges with three equivalent SYb2Bi4 octahedra. The corner-sharing octahedra tilt angles range from 5–36°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(YSe2)2 by Materials Project

Yb(YSe2)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Yb2+ is bonded to six Se2- atoms to form YbSe6 octahedra that share corners with six equivalent YSe6 octahedra, edges with two equivalent YbSe6 octahedra, and edges with six YSe6 octahedra. The corner-sharing octahedra tilt angles range from 1–4°. There are two shorter (2.94 Å) and four longer (2.98 Å) Yb–Se bond lengths. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six Se2- atoms to form YSe6 octahedra that share corners with six equivalent YbSe6 octahedra, edges with two equivalent YbSe6 octahedra, and edges with six YSe6 octahedra. The corner-sharing octahedra tilt angles range from 1–4°. There are two shorter (2.84 Å) and four longer (2.91 Å) Y–Se bond lengths. In the second Y3+ site, Y3+ is bonded to six Se2- atoms to form YSe6 octahedra that share edges with four equivalent YbSe6 octahedra and edges with six YSe6 octahedra. There are four shorter (2.87 Å) and two longer (2.89 Å) Y–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Yb2+ and three Y3+ atoms to form a mixture of corner and edge-sharing SeYb2Y3 square pyramids. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Yb2+ and three Y3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(GaSe2)2 by Materials Project

Yb(GaSe2)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. Yb2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are four shorter (3.13 Å) and four longer (3.18 Å) Yb–Se bond lengths. Ga3+ is bonded to four Se2- atoms to form edge-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.43–2.48 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Yb2+ and two equivalent Ga3+ atoms. In the second Se2- site, Se2- is bonded to two equivalent Yb2+ and two equivalent Ga3+ atoms to form a mixture of distorted edge and corner-sharing SeYb2Ga2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(CoP3)4 by Materials Project

Yb(CoP3)4 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Yb3+ is bonded to twelve equivalent P1- atoms to form YbP12 cuboctahedra that share faces with eight equivalent CoP6 octahedra. All Yb–P bond lengths are 2.98 Å. Co+2.25+ is bonded to six equivalent P1- atoms to form CoP6 octahedra that share corners with six equivalent CoP6 octahedra and faces with two equivalent YbP12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Co–P bond lengths are 2.25 Å. P1- is bonded in a 2-coordinate geometry to one Yb3+, two equivalent Co+2.25+, and two equivalent P1- atoms. There are one shorter (2.28 Å) and one longer (2.31 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(YSe2)2 by Materials Project

Yb(YSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Yb2+ is bonded to seven Se2- atoms to form distorted YbSe7 pentagonal bipyramids that share corners with eight YSe6 octahedra, edges with five YSe6 octahedra, edges with two equivalent YbSe7 pentagonal bipyramids, and faces with two equivalent YbSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 12–66°. There are a spread of Yb–Se bond distances ranging from 2.99–3.16 Å. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six Se2- atoms to form YSe6 octahedra that share corners with three equivalent YSe6 octahedra, corners with four equivalent YbSe7 pentagonal bipyramids, edges with six YSe6 octahedra, and an edgeedge with one YbSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Y–Se bond distances ranging from 2.85–2.94 Å. In the second Y3+ site, Y3+ is bonded to six Se2- atoms to form YSe6 octahedra that share corners with three equivalent YSe6 octahedra, corners with four equivalent YbSe7 pentagonal bipyramids, edges with four YSe6 octahedra, and edges with four equivalent YbSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Y–Se bond distances ranging from 2.85–2.90 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Yb2+ and three Y3+ atoms to form a mixture of distorted edge and corner-sharing SeYb2Y3 trigonal bipyramids. In the second Se2- site, Se2- is bonded to two equivalent Yb2+ and three Y3+ atoms to form SeYb2Y3 square pyramids that share corners with two equivalent SeYb3Y2 square pyramids, corners with two equivalent SeYb2Y3 trigonal bipyramids, edges with five SeYb2Y3 square pyramids, and edges with three equivalent SeYb2Y3 trigonal bipyramids. In the third Se2- site, Se2- is bonded to three equivalent Yb2+ and two equivalent Y3+ atoms to form a mixture of edge and corner-sharing SeYb3Y2 square pyramids. In the fourth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Y3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(CuS)2 by Materials Project

Yb(CuS)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent S2- atoms to form YbS6 octahedra that share corners with twelve equivalent CuS4 tetrahedra, edges with six equivalent YbS6 octahedra, and edges with six equivalent CuS4 tetrahedra. All Yb–S bond lengths are 2.78 Å. Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with six equivalent YbS6 octahedra, corners with six equivalent CuS4 tetrahedra, edges with three equivalent YbS6 octahedra, and edges with three equivalent CuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–54°. There are three shorter (2.36 Å) and one longer (2.42 Å) Cu–S bond lengths. S2- is bonded to three equivalent Yb2+ and four equivalent Cu1+ atoms to form a mixture of distorted edge and corner-sharing SYb3Cu4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(CuSe)3 by Materials Project

Yb(CuSe)3 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Yb3+ is bonded to six equivalent Se2- atoms to form YbSe6 octahedra that share corners with twelve equivalent CuSe4 tetrahedra, edges with three equivalent YbSe6 octahedra, and edges with six equivalent CuSe4 tetrahedra. All Yb–Se bond lengths are 2.91 Å. Cu1+ is bonded to four equivalent Se2- atoms to form CuSe4 tetrahedra that share corners with four equivalent YbSe6 octahedra, corners with six equivalent CuSe4 tetrahedra, edges with two equivalent YbSe6 octahedra, and edges with three equivalent CuSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–55°. There are a spread of Cu–Se bond distances ranging from 2.43–2.51 Å. Se2- is bonded in a 6-coordinate geometry to two equivalent Yb3+ and four equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A New Family of Proton‐Conducting Electrolytes for Reversible Solid Oxide Cells: BaHf x Ce 0.8− x Y 0.1 Yb 0.1 O 3− δ

Abstract Reversible solid oxide cells based on ceramic proton conductors have potential to be the most efficient system for large‐scale energy storage. The performance and long‐term durability of these systems, however, are often limited by the ionic conductivity or stability of the proton‐conducting electrolyte. Here new family of solid oxide electrolytes, BaHf x Ce 0.8− x Y 0.1 Yb 0.1 O 3− δ (BHCYYb), which demonstrate a superior ionic conductivity to stability trade‐off than the state‐of‐the‐art proton conductors, BaZr x Ce 0.8− x Y 0.1 Yb 0.1 O 3− δ (BZCYYb), at similar Zr/Hf concentrations, as confirmed by thermogravimetric analysis, Raman, and X‐ray diffraction analysis of samples over 500 h of testing are reported. The increase in performance is revealed through thermodynamic arguments and first‐principle calculations. In addition, lab scale full cells are fabricated, demonstrating high peak power densities of 1.1, 1.4, and 1.6 W cm −2 at 600, 650, and 700 °C, respectively. Round‐trip efficiencies for steam electrolysis at 1 A cm −2 are 78%, 72%, and 62% at 700, 650, and 600 °C, respectively. Finally, CO 2 H 2 O electrolysis is carried out for over 700 h with no degradation.

Murphy, Ryan↗
DOE OSTI2023

Stabilization Of The CN 3 5− Anion In Recoverable High‐pressure Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates

Abstract A series of isostructural Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high‐pressure (25–54 GPa) high‐temperature (2000–3000 K) conditions in laser‐heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single‐crystal X‐ray diffraction (SCXRD) as well as corroborated by X‐ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln 3 O 2 (CN 3 ) solids are composed of the hitherto unknown CN 3 5− guanidinate anion—deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln 3 O 2 (CN 3 ) compounds are recoverable to ambient conditions. The stabilization of the CN 3 5− guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.

Chemistry↗
DOE OSTI2023

Locating anionic hydrogen in Ba 3 (Yb,Lu) 2 O 5 H 2 : A combined approach of X-ray diffraction, crystal chemistry, and DFT calculations

By a combination of x-ray diffraction, structural chemistry, and DFT calculations, the presence and location of anionic hydrogen in the two new, layered lanthanide oxyhydrides, Ba 3 Ln 2 O 5 H 2 (Ln ​= ​Yb, Lu) is inferred. Single crystals of the compounds have been synthesized from a molten barium flux with the addition of small amounts of BaH 2 . These phases crystallize in space group I4/mmm (#139, Z ​= ​2) with lattice parameters a ​= ​4.3336(2) Å and c ​= ​22.7197(6) Å, and a ​= ​4.3291(1) Å and c ​= ​22.597(1) Å, respectively. The Ba 3 Ln 2 O 5 H 2 phases comprise two different structural moieties: a perovskite double layer of stoichiometry Ba 2 Ln 2 O 5 H – formed by corner-connected LnO 5 tetragonal bi-pyramids with a terminating hydrogen anion, and a puckered rocksalt-type (BaH) + layer that is stretched along the c-axis. DFT calculations were used to arrive at hydrogen positions that minimize energy and are consistent with structural chemistry principles. Furthermore, the calculations show that the valence band edge is dominated by oxygen 2p orbitals with hydrogen 1s states admixed. The conduction band is formed by barium 5d-orbitals and Lu (Yb) 5d-orbitals. These are characteristics of materials with anionic H – . These new phases are isostructural with the Ba 3 Ln 2 O 5 Cl 2 (Ln ​= ​Gd–Lu) family of compounds with the chlorine atom in the same apical position as the hydrogen atom. Finally, steric effects limit the size of the lanthanide ion for Ba 3 Ln 2 O 5 H 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Trends in Siting of Metals in Heterometallic Nd–Yb Metal–Organic Frameworks and Molecular Crystals

Several studies suggest that metal ordering within metal–organic frameworks (MOFs) is important for understanding how MOFs behave in relevant applications; however, these siting trends can be difficult to determine experimentally. To garner insight into the energetic driving forces that may lead to nonrandom ordering within heterometallic MOFs, we employ density functional theory (DFT) calculations on several bimetallic metal–organic crystals composed of Nd and Yb metal atoms. We also investigate the metal siting trends for a newly synthesized MOF. Our DFT-based energy of mixing results suggest that Nd will likely occupy sites with greater access to electronegative atoms and that local homometallic domains within a mixed-metal Nd–Yb system are favored. We also explore the use of less computationally extensive methods such as classical force fields and cluster expansion models to understand their feasibility for large system sizes. Here, this study highlights the impact of metal ordering on the energetic stability of heterometallic MOFs and crystal structures.

energy of mixing↗
DOE OSTI2022

Crystal Chemistry and Thermodynamics of HREE (Er, Yb) Mixing in a Xenotime Solid Solution

Rare earth elements (REEs), the 15 naturally occurring lanthanides plus yttrium and scandium, are ubiquitously used in modern life as they are critical components of many advanced devices and technologies. However, the demand for REEs is not equal, with the heavy rare earth elements (HREEs) having a higher demand. Xenotime (HREEPO 4 ) is an important HREE ore mineral and globally is an economical source of HREE. Most of the crystallographic and thermodynamic properties of xenotime endmembers have been elucidated by calorimetric, solubility, and high-pressure studies. Yet, in natural systems, endmembers are rarely encountered, and instead, REE solid solutions are more commonly observed. Here, we characterize the crystal chemistry, thermodynamics of HREE mixing, and high-temperature material behaviors and thermochemistry of a synthetic erbium (Er)-ytterbium (Yb) binary xenotime solid solution (Er (x) Yb (1-x) PO 4 ) using a suite of experimental techniques, including X-ray fluorescence spectroscopy, synchrotron X-ray powder diffraction implemented with Rietveld analysis, Fourier transform infrared spectroscopy coupled with attenuated total reflectance, Raman spectroscopy, thermogravimetric analysis coupled with differential scanning calorimetry, and high-temperature oxide melt drop solution calorimetry. Our results shed light on the formation of natural xenotimes and lay the foundation for their industrial applications as thermal coating materials.

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

Structural modulation and spin glassiness upon oxidation in oxygen storage material LnFeMnO 4+x for Ln = Y, Lu, and Yb

The mixed valence multiferroic LnFe 2+ Fe 3+ O 4 (where Ln = Y, Lu, and Yb) can reversibly uptake oxygen into its lattice, which is evidenced by a crystallographic phase transition along with the appearance of structural modulations. In this study, we show that the Mn-substituted version of this multiferroic can also be readily oxidized to LnFe 3+ Mn 3+ O 4.5 revealing similar oxygen storage behavior. Through neutron, electron, and synchrotron x-ray diffraction studies, we observe a structural modulation that we attribute to a displacement wave in the fully oxidized compound. This wave exhibits commensurability with a wavevector q = (-2/7, 1/7, 0). Bond valence summation analysis of plausible interstitial oxygen positions suggests that oxygen insertion likely occurs at the middle of the Fe/Mn–O bipyramid layers. The structural modulation of LnFeMnO 4.5 is two-dimensional, propagates along the ab-plane, and is highly symmetric as 12 identical modulation vectors are observed in the diffraction patterns. The nature of the lanthanide, Ln 3+ , does not seem to influence such modulations since we observe identical satellite reflections for all three samples of Ln = Y, Lu, and Yb. Both LnFeMnO 4 and LnFeMnO 4.5 display spin glassy behavior with 2D short-range magnetic ordering being observed in LnFeMnO 4 . Analysis of the neutron diffraction data reveals a correlation length of ~10 nm. Upon oxidation to LnFeMnO 4.5 , the short-range magnetic order is significantly suppressed.

36 MATERIALS SCIENCE↗