101 results on '"Toshiya, Otomo"'
Search Results
2. Generating Mechanism of Catalytic Effect for Hydrogen Absorption/Desorption Reactions in NaAlH4–TiCl3
- Author
-
Kazutaka Ikeda, Fumika Fujisaki, Toshiya Otomo, Hidetoshi Ohshita, Takashi Honda, Toru Kawamata, Hiroshi Arima, Kazumasa Sugiyama, Hitoshi Abe, Hyunjeong Kim, Kouji Sakaki, Yumiko Nakamura, Akihiko Machida, Toyoto Sato, Shigeyuki Takagi, and Shin-ichi Orimo
- Subjects
neutron diffraction ,X-ray diffraction ,anomalous X-ray scattering ,X-ray absorption fine structure ,hydrogen storage ,hydride complex ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The hydrogen desorption and absorption reactions of the complex metal hydride NaAlH4 are disproportionation processes, and the kinetics can be improved by adding a few mol% of Ti compounds, although the catalytic mechanism, including the location and state of Ti, remains unknown. In this study, we aimed to reveal the generating mechanism of catalytic Al–Ti alloy in NaAlH4 with TiCl3 using quantum multiprobe techniques such as neutron diffraction (ND), synchrotron X-ray diffraction (XRD), anomalous X-ray scattering (AXS), and X-ray absorption fine structure (XAFS). Rietveld refinements of the ND and XRD, profiles before the first desorption of NaAlD(H)4–0.02TiCl3 showed that Al in NaAlD(H)4 was partially substituted by Ti. On the other hand, Ti was not present in NaAlH4, and Al–Ti nanoparticles were detected in the XRD profile after the first re-absorption. This was consistent with the AXS and XAFS results. It is suggested that the substitution promotes the formation of a highly dispersed nanosized Al–Ti alloy during the first desorption process and that the effectiveness of TiCl3 as an additive can be attributed to the dispersion of Ti.
- Published
- 2021
- Full Text
- View/download PDF
3. Direct Observation of Scattering Angle Dependence of the Inelasticity Effect on the Interference Term Obtained from Time-of-Flight Neutron Diffraction Experiments
- Author
-
Yuko Amo, Kana Tsutsui, Toshiya Otomo, Yasuo Kameda, Takeshi Usuki, and Kazutaka Ikeda
- Subjects
Time of flight ,Angle dependence ,Interference (communication) ,Scattering ,Chemistry ,Intramolecular force ,biological sciences ,Neutron diffraction ,Direct observation ,General Chemistry ,Atomic physics ,Term (time) - Abstract
Scattering angle dependence has been experimentally examined for inelasticity effect on the intramolecular interference term observed from the time-of-flight neutron diffraction method. Internuclea...
- Published
- 2021
4. Origins of peaks of graphitic and pyrrolic nitrogen in N1s X-ray photoelectron spectra of carbon materials: quaternary nitrogen, tertiary amine, or secondary amine?
- Author
-
Satoshi Sato, Yasushi Nishikawa, Hayato Sato, Toshiya Otomo, Yasuhiro Yamada, and Tomofumi Kato
- Subjects
Materials science ,Tertiary amine ,Hydrogen ,Mechanical Engineering ,chemistry.chemical_element ,Crystallography ,symbols.namesake ,X-ray photoelectron spectroscopy ,chemistry ,Mechanics of Materials ,Halogen ,symbols ,General Materials Science ,Amine gas treating ,Graphite ,Raman spectroscopy ,Carbon - Abstract
X-ray photoelectron spectroscopy (XPS) is among the most powerful techniques to analyse structures of nitrogen-doped carbon materials. However, reported assignments of (1) graphitic nitrogen (N)/substitutional N, quaternary N (Q–N), or tertiary amine (T–N) and (2) pyrrolic N/secondary amine or T–N are questionable. Most reports assign peaks at ca. 401 eV as Q–N or graphitic N, whereas raw materials in most of those works contain neither counter anion nor halogen. Besides, the peak at ca. 400 eV has been assigned as pyrrolic N, but the presence of N–H is generally not confirmed. In this work, it was clarified that one of the reasons for the prevailing ambiguous assignments is the presence of N in heptagonal and pentagonal rings. The peaks at 400.1–401.2 eV were determined to be T–N, but not Q–N by analyzing graphitized polyimide (with the oxygen content of 0.01 at% or lower and the hydrogen content of 0 at%) using Raman spectroscopy, XPS, X-ray diffraction, total neutron scattering, elemental analysis, and molecular dynamics simulation. Besides, it was revealed that the peak at 400.1 eV originated from T–N on 5-membered rings or 7- and 5-membered rings, but not pyrrolic N because graphite including no hydrogen was used for analysis.
- Published
- 2021
5. Local Structure of Li+ in Superconcentrated Aqueous LiTFSA Solutions
- Author
-
Toshiya Otomo, Kazuhide Ueno, Yasuhiro Umebayashi, Hikari Watanabe, Erika Nozaki, Kazutaka Ikeda, Jihae Han, Kaoru Dokko, Masayoshi Watanabe, Nana Arai, Yasuo Kameda, and Kenta Fujii
- Subjects
Aqueous solution ,Coordination number ,Neutron diffraction ,chemistry.chemical_element ,Electrolyte ,Mole fraction ,Surfaces, Coatings and Films ,chemistry ,Materials Chemistry ,Physical chemistry ,Molecule ,Lithium ,Physical and Theoretical Chemistry ,Electrochemical window - Abstract
It has been reported that aqueous lithium ion batteries (ALIBs) can operate beyond the electrochemical window of water by using a superconcentrated electrolyte aqueous solution. The liquid structure, particularly the local structure of the Li+, which is rather different from conventional dilute solution, plays a crucial role in realizing the ALIB. To reveal the local structure around Li+, the superconcentrated LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) aqueous solutions were investigated by means of Raman spectroscopic experiments, high-energy X-ray total scattering measurements, and the neutron diffraction technique with different isotopic composition ratios of 6Li/7Li and H/D. The Li+ local structure changes with the increase of the LiTFSA concentration; the oligomer ([Lip(TFSA)q](p-q)+ (q > 2) forms at the molar fraction of LiTFSA (xLiTFSA) > 0.25. The average structure can be determined in which two water molecules and two oxygen atoms of TFSA anion(s) coordinate to the Li+ in the superconcentrated LiTFSA aqueous solution (LiTFSA)0.25(H2O)0.75. In addition, the intermolecular interaction between the neighboring water molecules was not found, and the hydrogen-bonded interaction in the solution should be significantly weak. According to the coordination number of the oxygen atom (TFSA or H2O), a variety of TFSA- and H2O coordination manners would exist in this solution; in particular, the oligomer is formed in which the monodentate TFSA cross-links Li+.
- Published
- 2021
6. Electrochemical, Thermal, and Structural Features of BaF2–SnF2 Fluoride-Ion Electrolytes
- Author
-
Toshiya Otomo, Takeshi Abe, Kazuhiro Mori, Atsushi Mineshige, Takuro Emoto, Kaoru Namba, Takashi Saito, Maiko Sugiura, and Toshiharu Fukunaga
- Subjects
chemistry.chemical_compound ,General Energy ,Materials science ,chemistry ,Thermal ,Inorganic chemistry ,Electrolyte ,Physical and Theoretical Chemistry ,Electrochemistry ,Fluoride ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion - Published
- 2021
7. Structural Investigation of Sulfonated Polyphenylene Ionomers for the Design of Better Performing Proton-Conductive Membranes
- Author
-
Junpei Miyake, Hiroshi Arima, Shin-ichi Takata, Toshiya Otomo, Kosuke Hiroi, Keisuke Shiino, Takeshi Yamada, and Kenji Miyatake
- Subjects
chemistry.chemical_classification ,Membrane ,Materials science ,Morphology (linguistics) ,Polymers and Plastics ,Proton ,Chemical engineering ,chemistry ,Process Chemistry and Technology ,Organic Chemistry ,Mechanical strength ,Polymer ,Electrical conductor - Abstract
To achieve high-performance proton-exchange membranes (PEMs), understanding of the polymer structure/property relationship is crucial. In particular, the structure of water clusters (number, size, ...
- Published
- 2020
8. Solvation Structure of Li+ in Concentrated Acetonitrile and N,N-Dimethylformamide Solutions Studied by Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods
- Author
-
Nana Arai, Kazutaka Ikeda, Yasuo Kameda, Takeshi Usuki, Kazuhide Ueno, Aoi Saji, Yuko Amo, Shu Saito, Yasuhiro Umebayashi, Toshiya Otomo, Kenta Fujii, and Hikari Watanabe
- Subjects
Neutron diffraction ,Intermolecular force ,Solvation ,Analytical chemistry ,chemistry.chemical_element ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Solvation shell ,chemistry ,Amide ,Materials Chemistry ,Molecule ,Lithium ,Physical and Theoretical Chemistry ,Acetonitrile - Abstract
Neutron diffraction measurements on 6Li/7Li isotopically substituted 10 and 33 mol % *LiTFSA (lithium bis(trifluoromethylsulfonyl)amide)-AN-d3 (acetonitrile-d3) and 10 and 33 mol % *LiTFSA-DMF-d7(N,N-dimethylformamide-d7) solutions have been carried out in order to obtain structural insights on the first solvation shell of Li+ in highly concentrated organic solutions. Structural parameters concerning the local structure around Li+ have been determined from the least squares fitting analysis of the first-order difference function derived from the difference between carefully normalized scattering cross sections observed for 6Li-enriched and natural abundance solutions. In 10 mol % LiTFSA-AN-d3 solution, 3.25 ± 0.04 AN molecules are coordinated to Li+ with a intermolecular Li+···N(AN) distance of 2.051 ± 0.007 A. It has been revealed that 1.67 ± 0.07 AN molecules and 2.00 ± 0.01 TFSA- are involved in the first solvation shell of Li+ in the 33 mol % LiTFSA-AN solution. The nearest neighbor Li+···NAN and Li+···OTFSA- distances are obtained to be r(Li+···N) = 2.09 ± 0.01 A and r(Li+···O) = 1.88 ± 0.01 A, respectively. The first solvation shell of Li+ in the 10 mol % LiTFSA-DMF-d7 solutions contains 3.4 ± 0.1 DMF molecules with an intermolecular Li+···ODMF distance of 1.95 ± 0.02 A. In highly concentrated 33 mol % LiTFSA-DMF-d7 solutions, there are 1.3 ± 0.2 DMF molecules and 3.2 ± 0.2 TFSA- in the first solvation shell of Li+ with intermolecular distances of r(Li+···ODMF) = 1.90 ± 0.02 A and r(Li+···OTFSA-) = 2.01 ± 0.01 A, respectively. The Li+···TFSA- contact ion pair stably exists in highly concentrated 33 mol % LiTFSA-AN and -DMF solutions.
- Published
- 2020
9. Crystal Structural Investigations for Understanding the Hydrogen Storage Properties of YMgNi4‑Based Alloys
- Author
-
Kazutaka Ikeda, Loris Lombardo, Takashi Honda, Toyoto Sato, Wen Luo, Andreas Züttel, Hajime Sagayama, H.N. Yang, Shigeyuki Takagi, Tomohiro Mochizuki, Tatsuoki Kono, Shin Ichi Orimo, and Toshiya Otomo
- Subjects
Materials science ,Hydrogen ,mg2-xprxni4 ,Hydride ,General Chemical Engineering ,Neutron diffraction ,diffraction ,chemistry.chemical_element ,General Chemistry ,Crystal structure ,Article ,ce ,x=0.6 ,Crystal ,Hydrogen storage ,thermodynamics ,Chemistry ,Deuterium ,chemistry ,Phase (matter) ,Physical chemistry ,hydriding properties ,rietveld refinement ,QD1-999 - Abstract
The hydrogen storage properties and crystal structures of YMgNi4-based alloys, which were synthesized from (2 - x)YNi2 and xMgNi(2) (0.6
- Published
- 2020
10. Structural and Electrochemical Properties of Tysonite Ce0.95A0.05F2.95 (A = Mg, Ca, Sr, and Ba): Fast-Fluoride-Ion-Conducting Solid Electrolytes
- Author
-
Takashi Saito, Toshiya Otomo, Yoshiyuki Morita, Takeshi Abe, Toshiharu Fukunaga, Takashi Kamiyama, and Kazuhiro Mori
- Subjects
Materials science ,Inorganic chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,General Energy ,chemistry ,Electrode ,Fast ion conductor ,Physical and Theoretical Chemistry ,0210 nano-technology ,Fluoride - Abstract
All-solid-state fluoride shuttle batteries (FSBs) present endless possibilities for next-generation rechargeable batteries. However, no standard choice for solid electrolytes and electrodes in FSBs...
- Published
- 2020
11. High-pressure Synthesis of Ba2CoO2Ag2Te2 with Extended CoO2 Planes
- Author
-
Yusuke Nambu, Kazutaka Ikeda, Hiroshi Kageyama, Takashi Honda, Yuki Matsumoto, and Toshiya Otomo
- Subjects
Inorganic Chemistry ,Crystallography ,Group (periodic table) ,Chemistry ,High pressure ,Physical and Theoretical Chemistry ,Space (mathematics) - Abstract
Using a high-pressure synthesis method, we prepared the layered oxychalcogenide Ba2CoO2Ag2Te2 (space group: I4/mmm) with alternating stacks of CoO2 and Ag2Te2 layers, separated by Ba atoms. The CoO...
- Published
- 2020
12. Titanium Hydride Complex BaCa2Ti2H14 with 9-Fold Coordination
- Author
-
Hotaka Nakajima, Kazutaka Ikeda, Takashi Honda, Hikaru Takeda, Toshiya Otomo, Takeshi Yajima, and Zenji Hiroi
- Subjects
Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,Chemistry ,Band gap ,Valence band ,Titanium hydride ,Fold (geology) ,Crystal structure ,Physical and Theoretical Chemistry ,Valence electron - Abstract
We present the high-pressure synthesis and crystal structure of a novel titanium hydride complex, BaCa2Ti2H14, with 9-fold coordination. It comprises a unique dinuclear [Ti2H14]6– complex that cons...
- Published
- 2020
13. Experimental Visualization of Interstitialcy Diffusion Pathways in Fast-Fluoride-Ion-Conducting Solid Electrolyte Ba0.6La0.4F2.4
- Author
-
Takashi Kamiyama, Toshiya Otomo, Yoshihisa Ishikawa, Atsushi Mineshige, Maiko Sugiura, Kaoru Namba, Kazuhiro Mori, Fumika Fujisaki, Toshiharu Fukunaga, Takashi Saito, and Takeshi Abe
- Subjects
Materials science ,Neutron diffraction ,Energy Engineering and Power Technology ,Maximum entropy method ,Electrolyte ,Ion ,Visualization ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,Diffusion (business) ,Fluoride - Abstract
All-solid-state fluoride shuttle batteries (FSBs) have the potential to become the next generation of rechargeable batteries. However, there are gaps in the fundamentals of developing all-solid-sta...
- Published
- 2020
14. Hydrogen storage by earth-abundant metals, synthesis and characterization of Al3FeH3.9
- Author
-
Shin Ichi Orimo, Toyoto Sato, Tomitsugu Taguchi, Tetsu Watanuki, Tetsuya Yamaki, Hiroyuki Saitoh, Toshiya Otomo, Kazutaka Ikeda, Shunya Yamamoto, Shigeyuki Takagi, Mai Tanikami, and Akihiko Machida
- Subjects
Materials science ,Hydrogen ,business.industry ,Mechanical Engineering ,Neutron diffraction ,In situ synchrotron radiation X-ray powder diffraction measurement ,chemistry.chemical_element ,Rietveld refinement ,Crystal structure ,High pressure and high temperature ,Al-Fe hydrides ,Chemical state ,Hydrogen storage ,chemistry ,Transition metal ,Mechanics of Materials ,Chemical physics ,Hydrogen economy ,TA401-492 ,General Materials Science ,Chemical stability ,business ,Materials of engineering and construction. Mechanics of materials - Abstract
Among the various functionalities of hydrides, their use in hydrogen storage has been the most intensively studied because hydrides can store hydrogen compactly and safely. Thus, hydrides are key materials for the hydrogen economy. Here, the hydrogen storage material Al3FeH3.9 has been synthesized from cost-effective earth-abundant metals, Fe and Al. Hydrides consisting of Al and transition metals with low hydrogen affinities are rare because such alloys are unstable. However, it is expected that appropriate mixing of the chemical states of hydrogen atoms would allow synthesis of Al-Fe hydrides. The experimentally determined crystal structure of Al3FeD3.9 suggests realization of the mixing of the chemical state of hydrogen. Al3FeH3.9 is more thermodynamically stable than AlH3, and it is likely that the mixing of the chemical state of hydrogen atoms is the source of increased stability. The results of this study confirm that by controlling the chemical states of hydrogen, it is possible to tune the thermodynamic stability of hydrides and thus realize novel functional hydrides.
- Published
- 2021
15. Generating Mechanism of Catalytic Effect for Hydrogen Absorption/Desorption Reactions in NaAlH4–TiCl3
- Author
-
Takashi Honda, Toru Kawamata, Fumika Fujisaki, Akihiko Machida, Kazutaka Ikeda, Kazumasa Sugiyama, Yumiko Nakamura, Hyunjeong Kim, Shin Ichi Orimo, Hiroshi Arima, Toyoto Sato, Hidetoshi Ohshita, Hitoshi Abe, Kouji Sakaki, Shigeyuki Takagi, and Toshiya Otomo
- Subjects
X-ray absorption fine structure ,Technology ,Materials science ,QH301-705.5 ,QC1-999 ,Neutron diffraction ,anomalous X-ray scattering ,Catalysis ,hydrogen storage ,Hydrogen storage ,neutron diffraction ,Desorption ,General Materials Science ,Biology (General) ,Instrumentation ,QD1-999 ,Fluid Flow and Transfer Processes ,Process Chemistry and Technology ,Physics ,General Engineering ,Engineering (General). Civil engineering (General) ,hydride complex ,Computer Science Applications ,X-ray diffraction ,Chemistry ,X-ray crystallography ,Physical chemistry ,Complex metal hydride ,Anomalous X-ray scattering ,TA1-2040 - Abstract
The hydrogen desorption and absorption reactions of the complex metal hydride NaAlH4 are disproportionation processes, and the kinetics can be improved by adding a few mol% of Ti compounds, although the catalytic mechanism, including the location and state of Ti, remains unknown. In this study, we aimed to reveal the generating mechanism of catalytic Al–Ti alloy in NaAlH4 with TiCl3 using quantum multiprobe techniques such as neutron diffraction (ND), synchrotron X-ray diffraction (XRD), anomalous X-ray scattering (AXS), and X-ray absorption fine structure (XAFS). Rietveld refinements of the ND and XRD, profiles before the first desorption of NaAlD(H)4–0.02TiCl3 showed that Al in NaAlD(H)4 was partially substituted by Ti. On the other hand, Ti was not present in NaAlH4, and Al–Ti nanoparticles were detected in the XRD profile after the first re-absorption. This was consistent with the AXS and XAFS results. It is suggested that the substitution promotes the formation of a highly dispersed nanosized Al–Ti alloy during the first desorption process and that the effectiveness of TiCl3 as an additive can be attributed to the dispersion of Ti.
- Published
- 2021
16. Facile Synthesis of LiH-Stabilized Face-Centered-Cubic YH3 High-Pressure Phase by Ball Milling Process
- Author
-
Toru Kimura, Atsunori Kamegawa, Nobuhiko Takeichi, Kouji Sakaki, Masashi Nozaki, Toshikatsu Kojima, Toshiya Otomo, Kazutaka Ikeda, and Riki Kataoka
- Subjects
Hydrogen ,010405 organic chemistry ,Analytical chemistry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallinity ,symbols.namesake ,chemistry ,Phase (matter) ,Desorption ,symbols ,Thermal stability ,Physical and Theoretical Chemistry ,Raman spectroscopy ,Ball mill ,Ambient pressure - Abstract
A face-centered-cubic (FCC) YH3 phase is known to be stable only under high pressure (HP) of more than gigapascal order, and it reverts to the hexagonal YH3 ambient-pressure phase when the pressure is released. We previously found that the FCC YH3 can be stabilized even at ambient pressure by substituting Y for 10 mol % Li (LiH-stabilized YH3, LSY). The LSY was synthesized by heat treatment under gigapascal HP, but this process is unfavorable for mass production; that is, only a few tens of milligrams of a sample can be obtained in a single batch. In this study, we overcame this problem by applying a ball milling (BM) process for synthesizing the LSY phase, and the yield by the BM process reached on the order of grams. We confirmed that the structure of the BM sample was the same as that of the HP sample by X-ray diffractometry, Raman spectroscopy, and neutron total scattering pair distribution function analyses. The crystallinity of the BM sample, however, was lower than that of the HP sample. The difference in the crystallinity affects the thermal stability of the LSY. The BM sample with a lower crystallinity released hydrogen at a lower temperature. The BM sample was found to reversibly desorb/absorb hydrogen maintaining its initial FCC structure when the rehydrogenation temperature was at 423 K. However, when the rehydrogenation temperature of BM sample was more than 573 K, the FCC structure changed to the hexagonal ambient pressure phase due to thermal instability of FCC phase for the BM sample.
- Published
- 2019
17. Characteristic fast H− ion conduction in oxygen-substituted lanthanum hydride
- Author
-
Hideo Hosono, Kazutaka Ikeda, Masato Sasase, Soshi Iimura, Takashi Honda, Tomofumi Tada, Satoru Fujitsu, Hiromu Tamatsukuri, Keiga Fukui, and Toshiya Otomo
- Subjects
0301 basic medicine ,Materials science ,Science ,Enthalpy ,Analytical chemistry ,General Physics and Astronomy ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,Conductivity ,General Biochemistry, Genetics and Molecular Biology ,Article ,Ion ,03 medical and health sciences ,Batteries ,Lanthanum ,Electrochemistry ,Ionic conductivity ,lcsh:Science ,Multidisciplinary ,Hydride ,General Chemistry ,Solid-state chemistry ,021001 nanoscience & nanotechnology ,Thermal conduction ,030104 developmental biology ,chemistry ,lcsh:Q ,0210 nano-technology - Abstract
Fast ionic conductors have considerable potential to enable technological development for energy storage and conversion. Hydride (H−) ions are a unique species because of their natural abundance, light mass, and large polarizability. Herein, we investigate characteristic H− conduction, i.e., fast ionic conduction controlled by a pre-exponential factor. Oxygen-doped LaH3 (LaH3−2xOx) has an optimum ionic conductivity of 2.6 × 10−2 S cm−1, which to the best of our knowledge is the highest H− conductivity reported to date at intermediate temperatures. With increasing oxygen content, the relatively high activation energy remains unchanged, whereas the pre-exponential factor decreases dramatically. This extraordinarily large pre-exponential factor is explained by introducing temperature-dependent enthalpy, derived from H− trapped by lanthanum ions bonded to oxygen ions. Consequently, light mass and large polarizability of H−, and the framework comprising densely packed H− in LaH3−2xOx are crucial factors that impose significant temperature dependence on the potential energy and implement characteristic fast H− conduction., Hydride ions are promising for energy storage since they are abundant, lightweight, and highly mobile, but ionic conductivity should be improved. Here the authors achieve fast hydride ion conductivity in a mixed-anion compound by tuning oxygen content.
- Published
- 2019
18. Solvation Structure of Li+ in Methanol and 2-Propanol Solutions Studied by ATR-IR and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods
- Author
-
Koichi Sato, Yuko Amo, Toshiya Otomo, Kazutaka Ikeda, Ryo Hasebe, Yasuhiro Umebayashi, Takeshi Usuki, and Yasuo Kameda
- Subjects
Coordination number ,Neutron diffraction ,Intermolecular force ,Solvation ,Mole fraction ,Surfaces, Coatings and Films ,Propanol ,chemistry.chemical_compound ,Solvation shell ,chemistry ,Attenuated total reflection ,Materials Chemistry ,Physical chemistry ,Physical and Theoretical Chemistry - Abstract
Neutron diffraction measurements have been carried out on 10 mol % LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) solutions in methanol- d4 and 2-propanol- d8 to obtain information on the solvation structure of Li+. The detailed coordination structure of solvent molecules within the first solvation shell of Li+ was determined through the least-squares fitting analysis of the difference function between normalized scattering cross sections observed for 6Li/7Li isotopically substituted sample solutions. The nearest-neighbor Li+···O distance and coordination number determined for the 10 mol % LiTFSA-methanol- d4 solution are rLiO = 1.98 ± 0.02 A and nLiO = 3.8 ± 0.6, respectively. In the 2-propanol- d8 solution, it has been revealed that 2-propanol- d8 molecules within the first solvation shell of Li+ take at least two different coordination geometries with the intermolecular nearest-neighbor Li+···O distance of rLiO = 1.93 ± 0.04 A. The Li+···O coordination number, nLiO = 3.3 ± 0.3, is determined. Ion-pair formation in the LiTFSA-methanol and LiTFSA-2-propanol solutions has been investigated by the attenuated total reflection infrared spectroscopic method. Mole fractions of free, Li+-bound, and aggregated TFSA- are derived from the peak deconvolution analysis of vibrational bands observed for TFSA-.
- Published
- 2019
19. Origin of the Difference in Ion-Water Distances Determined by X-ray and Neutron Diffraction Measurements for Aqueous NaCl and KCl Solutions
- Author
-
Toshiya Otomo, Kazutaka Ikeda, Yasuhiro Umebayashi, Yasuo Kameda, Yuko Amo, and Takeshi Usuki
- Subjects
Aqueous solution ,010405 organic chemistry ,Chemistry ,Astrophysics::High Energy Astrophysical Phenomena ,Intermolecular force ,Neutron diffraction ,X-ray ,Analytical chemistry ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,biological sciences - Abstract
Experimental evidence has been presented on the difference in intermolecular ion-water distances obtained from X-ray and neutron diffraction methods. Simultaneous least squares fitting procedures w...
- Published
- 2019
20. Zeolitic Intermetallics: LnNiSi (Ln = La–Nd)
- Author
-
Kazutaka Ikeda, Hideo Hosono, Masaaki Kitano, Sangwon Park, Kazuhisa Kishida, Hiroshi Mizoguchi, Junghwan Kim, Masato Sasase, Toshiya Otomo, and Takashi Honda
- Subjects
Hydrogen ,Chemistry ,Intermetallic ,chemistry.chemical_element ,General Chemistry ,Electron ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Redox ,Catalysis ,0104 chemical sciences ,Ammonia production ,Metal ,Crystallography ,Colloid and Surface Chemistry ,visual_art ,visual_art.visual_art_medium ,Cavity wall ,Ambient pressure - Abstract
LnNiSi (Ln = La-Nd) comprising a three-dimensional NiSi framework has electrons in the crystallographic cavity space. In the temperature region 473-773 K, it accepts the insertion/de-insertion of hydrogen topotactically without a change in unitcell volume. The insertion of hydrogens into the cavity space is accompanied by a redox reaction with the orbitals of atoms constituting the cavity wall. Having small work functions, such intermetallic electrides exhibit metallic electrical and magnetic properties. Owing to a high electron-donating power and reversible exchange between hydrogen and the electrons, Ru5wt%-loaded LaNiSi powder worked as an efficient catalyst for ammonia synthesis under ambient pressure.
- Published
- 2019
21. Nephelauxetic effect of the hydride ligand in Sr2LiSiO4H as a host material for rare-earth-activated phosphors
- Author
-
Kazutaka Ikeda, Hiromu Tamatsukuri, Tong Wu, Satoru Matsuishi, Asako Ishikawa, Toshiya Otomo, and Takashi Honda
- Subjects
Nephelauxetic effect ,Photoluminescence ,Materials science ,Rietveld refinement ,Hydride ,General Chemical Engineering ,chemistry.chemical_element ,Phosphor ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Crystallography ,chemistry.chemical_compound ,chemistry ,Lithium ,Orthosilicate ,Isostructural ,0210 nano-technology - Abstract
Strontium lithium orthosilicate hydride Sr2LiSiO4H was synthesized by the reaction of Sr2SiO4 with LiH at 700 °C in a H2 rich atmosphere. Rietveld refinement of the neutron powder diffraction pattern revealed that Sr2LiSiO4H is isostructural to Sr2LiSiO4F (space group P21/m) and its channel-like structure preferentially accommodates H− ions over F− ions. In addition, Sr2LiSiO4H is stable in air and its Eu2+-doped analog exhibits yellow photoluminescence with an emission band at 544 nm and a broad excitation band ranging from 250 to 450 nm. These bands were observed in the longer wavelength region when compared with those displayed by Sr2LiSiO4F:Eu2+. The red shift, which is induced by H− substitution, is consistent with the constrained density functional theory calculations, predicting the photo-excitation and emission energies of 4f–5d transitions. The present study reports the synthesis of stable oxyhydrides acting as phosphor hosts for rare earth ions. The phosphor hosts exhibit large nephelauxetic effects owing to the presence of H− ligands.
- Published
- 2019
22. Neutron Diffraction Study on Partial Pair Correlation Functions of Water at Ambient Temperature
- Author
-
Kazutaka Ikeda, Yuko Amo, Takeshi Usuki, Toshiya Otomo, Yasuhiro Umebayashi, and Yasuo Kameda
- Subjects
010304 chemical physics ,Liquid water ,Chemistry ,Intermolecular force ,Neutron diffraction ,Analytical chemistry ,General Chemistry ,01 natural sciences ,Condensed Matter::Soft Condensed Matter ,Pair correlation ,biological sciences ,0103 physical sciences ,X-ray crystallography ,Nuclear Experiment ,010306 general physics - Abstract
A new determination is presented for the intermolecular partial pair correlation functions of liquid water at ambient temperature. Time-of-flight (TOF) neutron diffraction measurements with excelle...
- Published
- 2018
23. Mechanochemical synthesis of binary phosphorus telluride: Short range structure and thermal properties
- Author
-
Keiji Itoh, Toshiya Otomo, and Y. Mizuhara
- Subjects
Materials science ,Neutron diffraction ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Telluride ,Materials Chemistry ,Ceramics and Composites ,Sublimation (phase transition) ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tellurium ,Structure factor ,Thermal analysis - Abstract
A binary phosphorus telluride sample (20 at% Te) was synthesized by mechanochemical solid state reaction from elemental powders. The X-ray diffraction pattern and neutron total structure factor show no detectable Bragg peaks, indicating that the sample is amorphous with respect to X-ray and neutron diffraction. The neutron and X-ray total pair distribution functions show correlation peak arising from P Te heteropolar bonds in addition to those arising from P P and Te Te bonds. The Te Te bond length is slightly shorter than that in the crystal structure of trigonal tellurium, suggesting a different environment from a polymeric chain structure. The thermal analysis results show that the binary phosphorus telluride is thermally unstable, that is, it decomposes above 200 °C into trigonal tellurium crystals and gaseous phosphorus, where phosphors begins to gasify at a lower temperature than the sublimation temperature of red phosphors.
- Published
- 2018
24. Suppression of the Phase Coexistence of the fcc-fct Transition in Hafnium-Hydride Thin Films
- Author
-
Kouji Sakaki, Kohta Asano, Kazutaka Ikeda, Bernard Dam, Herman Schreuders, Shigenobu Hayashi, Toshiya Otomo, Hyunjeong Kim, and L. J. Bannenberg
- Subjects
Diffraction ,Materials science ,Letter ,Hydrogen ,business.industry ,Hydride ,chemistry.chemical_element ,Hafnium ,Metal ,chemistry ,Chemical physics ,Hydrogen economy ,Phase (matter) ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Physical and Theoretical Chemistry ,Thin film ,business - Abstract
Metal hydrides may play a paramount role in a future hydrogen economy. While most applications are based on nanostructured and confined materials, studies considering the structural response of these materials to hydrogen concentrate on bulk material. Here, using in situ in- and out-of-plane X-ray diffraction and reflectometry, we study the fcc ↔ fct transition in Hf thin films, an optical hydrogen-sensing material. We show that the confinement of Hf affects this transition: compared to bulk Hf, the transition is pushed to a higher hydrogen-to-metal ratio, the tetragonality of the fct phase is reduced, and phase coexistence is suppressed. These nanoconfinement effects ensure the hysteresis-free response of hafnium to hydrogen, enabling its remarkable performance as a hydrogen-sensing material. In a wider perspective, the results highlight the profound influences of the nanostructuring and nanoconfinement of metal hydrides on their structural response to hydrogen with a significant impact on their applicability in future devices.
- Published
- 2021
25. Structural Variation of Self-Organized Mg Hydride Nanoclusters in Immiscible Ti Matrix by Hydrogenation
- Author
-
Kohta Asano, Kouji Sakaki, Yumiko Nakamura, Hyunjeong Kim, Keiko Jimura, Kazutaka Ikeda, Toshiya Otomo, Tetsu Watanuki, Akihiko Machida, and Shigenobu Hayashi
- Subjects
Scattering ,Hydride ,Chemistry ,Alloy ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surface energy ,0104 chemical sciences ,Nanoclusters ,Inorganic Chemistry ,Metal ,Condensed Matter::Materials Science ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Magic angle spinning ,engineering ,Orthorhombic crystal system ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Hydrogenation of nonequilibrium alloys may form nanometer-sized metal hydride clusters, depending on the alloy compositions and hydrogenation conditions. Here in the Ti-rich compositions of the immiscible Mg-Ti system MgH2 clusters are embedded in a Ti-H matrix. Our previous works have indicated that the interface energy between the two metal hydrides reduces the stability of MgH2. The aim of our study is to obtain the structural information on the nanometer-sized clusters. Indeed, MgD2 clusters embedded in a face-centered-cubic (FCC) Ti-D matrix is found in Mg0.25Ti0.75D1.65 by means of 2H magic angle spinning nuclear magnetic resonance (MAS NMR). The atomic pair distribution function (PDF) analysis of neutron total scattering data suggests that the MgD2 clusters have an orthorhombic structure, which is different from a rutile-type body-centered-tetragonal (BCT) structure of α-MgD2 observed in the Mg-rich compositions. Our results suggest that we can tune the thermodynamics of hydrogen absorption and des...
- Published
- 2018
26. AgFeOF2: A Fluorine-Rich Perovskite Oxyfluoride
- Author
-
Takafumi Yamamoto, Cédric Tassel, Jun Kikkawa, Saburo Hosokawa, Koji Kimoto, Toshiya Otomo, Kazunari Arai, Takashi Honda, Kazutaka Ikeda, Fumitaka Takeiri, Hiroshi Kageyama, and Naoaki Hayashi
- Subjects
Chemistry ,Neutron diffraction ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,Octahedron ,Superexchange ,Mössbauer spectroscopy ,Fluorine ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Absorption (chemistry) ,0210 nano-technology ,Perovskite (structure) - Abstract
We synthesized a silver iron oxyfluoride AgFeOF2 by using a high-pressure reaction. Synchrotron X-ray and neutron diffraction, X-ray absorption, and 57Fe Mossbauer spectroscopy indicate that AgFeOF2 crystallizes in the ideal perovskite structure with iron in a trivalent state, although electron microscopy revealed weak super-reflections. A possible partial ordering in the FeO2F4 octahedron is inferred from Mossbauer spectroscopy. The synthesis of the fluorine-rich sample offers an opportunity to study a composition-property relation in AFeIIIO3–nFn (n = 0, 1, and 2). AgFeOF2 exhibits a G-type antiferromagnetic ordering below TN ≈ 480 K, which is much lower than the n = 0 and 1 cases, suggesting a weaker superexchange interaction between Fe moments via F 2p orbitals (vs O 2p orbitals).
- Published
- 2018
27. Graphene-based ordered framework with a diverse range of carbon polygons formed in zeolite nanochannels
- Author
-
Patrick Bonnaud, Minoru T. Miyahara, Kazutaka Ikeda, Toshiya Otomo, Naoto Miyamoto, Hiroyuki Fujimoto, Ryuji Miura, Akira Miyamoto, Hirotomo Nishihara, Hideki Tanaka, Nozomu Hatakeyama, Takashi Kyotani, Hiroyuki Itoi, Ai Suzuki, and Keita Nomura
- Subjects
Diffraction ,Materials science ,Similarity (geometry) ,Graphene ,Neutron diffraction ,chemistry.chemical_element ,Pair distribution function ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry ,law ,Chemical physics ,General Materials Science ,Heptagon ,0210 nano-technology ,Carbon ,BET theory - Abstract
With the aim of understanding three-dimensional graphene-based frameworks in detail, a realistic structure model of zeolite-templated carbon (ZTC) is constructed by using computer simulation, and its simulated physical properties are compared with experimental data. The proposed structure model provides the insight into a unique X-ray diffraction pattern of ZTC: disordered building units comprised of curved and non-stacked graphene fragments are connected along the ordered zeolite nanochannels, forming a long-range structure order derived from zeolite (111) and (220) planes. Though ZTC is one of the superporous carbons with a very large Brunauer–Emmett–Teller (BET) surface area (3935 m2 g−1), the simulation study indicates a possibility to achieve further higher BET surface area up to 4845 m2 g−1. Moreover, the presence of carbon polygons other than hexagon in graphene matrices is analyzed by a high-resolution pair distribution function obtained from neutron diffraction measurement. The comparison between experimental data and simulation suggests that ZTC framework contains a diverse range of carbon polygons such as hexagons, heptagons and octagons, while pentagons are minor. Such distribution of carbon polygons demonstrates interesting similarity between the real three-dimensional graphene-based framework and imaginary ones like Mackay crystals and carbon Schwarzites.
- Published
- 2018
28. Local Structure of Li+ in Concentrated Ethylene Carbonate Solutions Studied by Low-Frequency Raman Scattering and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods
- Author
-
Takeshi Usuki, Toshiya Otomo, Yasuhiro Umebayashi, Yuko Amo, Maho Yanagisawa, Shunya Maeda, Yasuo Kameda, Hikari Watanabe, Nana Arai, Shiro Seki, and Kazutaka Ikeda
- Subjects
Neutron diffraction ,Isotropy ,Analytical chemistry ,02 engineering and technology ,Neutron scattering ,Low frequency ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,symbols.namesake ,Crystallography ,Molecular geometry ,chemistry ,Materials Chemistry ,symbols ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Ethylene carbonate ,Raman scattering - Abstract
Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+···TFSA–, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+···TFSA– ion pair were observed at ν = 168–177 and 202–224 cm–1, respectively. Detailed structural properties of solvated Li+ and Li+···TFSA– contact ion pair were derived from the least-squares fitting analysis of first-order difference function, ΔLi(Q), between neutron scattering cross sections observed for 6Li/7Li isotopically substituted 10 and 25 mol % *LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+···O(EC) distance and Li+···O(EC)═C(EC) bond angle are determined to be 1.90 ± 0.01 A and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC ...
- Published
- 2017
29. Transformation of the Chromium Coordination Environment in LaCrAsO Induced by Hydride Doping: Formation of La2Cr2As2OyHx
- Author
-
Sangwon Park, Hideo Hosono, Toshiya Otomo, Kazutaka Ikeda, Hiroshi Mizoguchi, and Haruhiro Hiraka
- Subjects
Hydrogen ,Dopant ,Chemistry ,Hydride ,Coordination number ,Inorganic chemistry ,Doping ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Chromium ,Crystallography ,Transition metal ,Physical and Theoretical Chemistry ,0210 nano-technology ,Solid solution - Abstract
We report the synthesis of La2Cr2As2OyHx (0.1 < y < 1.6) oxyhydride solid solutions using a solid-state reaction under high pressure with a solid-state hydrogen source and exhibit an example of how H– doping can also promote structural changes: H– doping in LaCrAsO results in the formation of La2Cr2As2OyHx with the La2Fe2Se2O3-type layered structure. Remarkably, this transformation includes a change of the coordination number of Cr from 4 to 6, with the some of the H– being accommodated in new sites within the CrAs layers. In this way, H– not only serves as a conventional electron dopant by the substitution of O2– but also makes new bonds to the transition metals.
- Published
- 2017
30. Insights from ab initio molecular dynamics simulations for a multicomponent oxide glass
- Author
-
Eiji Tsuchida, Kenzo Deguchi, Shinobu Ohki, Toshiya Otomo, Takahiro Ohkubo, Tadashi Shimizu, and Yasuhiko Iwadate
- Subjects
Chemistry ,Component (thermodynamics) ,Neutron diffraction ,Oxide ,02 engineering and technology ,Nuclear magnetic resonance spectroscopy ,021001 nanoscience & nanotechnology ,Ring (chemistry) ,01 natural sciences ,Bond length ,Crystallography ,Trigonal bipyramidal molecular geometry ,chemistry.chemical_compound ,Chemical physics ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,010306 general physics ,0210 nano-technology ,Coordination geometry - Abstract
It remains a challenge to establish structural models of multi component oxide glass systems. In this study, we have investigated 68.3 SiO2-16.1B2O3-4.2 Al2O3-11.4 Na2O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against 17O solid- state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five- coordinate Si (SiV) and Al (AlV). The SiV-O bond lengths and O-SiV-O angle distribution in the glass indicated 1.718 Ǻ and three peaks at 90◦, 120◦, and 175◦, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that SiV and AlV were found to preferentially contribute to the formation of small ring sizes. This article is protected by copyright. All rights reserved.
- Published
- 2017
31. Mechanical synthesis and structural properties of the fast fluoride-ion conductor PbSnF4
- Author
-
Takashi Kamiyama, Eiichiro Matsubara, Masao Yonemura, Toshiharu Fukunaga, Fumika Fujisaki, Kazuhiro Mori, Toshiya Otomo, and Yoshihisa Ishikawa
- Subjects
Phase transition ,Materials science ,Neutron diffraction ,Analytical chemistry ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,chemistry ,Electrical resistivity and conductivity ,X-ray crystallography ,Materials Chemistry ,Ceramics and Composites ,Physical and Theoretical Chemistry ,0210 nano-technology ,Fluoride - Abstract
A fluoride-ion conductor, γ-PbSnF4, was synthesized by the mechanical milling. In addition, β-PbSnF4 was obtained by aging the γ-PbSnF4 at 473 K. The electrical conductivity of β-PbSnF4 is relatively higher than that of γ-PbSnF4 at 298 K. The crystal structure analysis of γ- and β-PbSnF4 was carried out using neutron diffraction data. From the obtained occupancies, fluoride ions were located at the Fγ(1) normal site (62%) and Fγ(2) interstitial site (38%) in γ-PbSnF4 and the Fβ(1) normal site (31%), Fβ(2) normal site (25%), and Fβ(3) interstitial site (44%) in β-PbSnF4. In particular, the number of fluoride ions at the F interstitial site increased after the γ-to-β phase transition: 38% at Fγ(2) to 44% at Fβ(3). It is most likely that the ratio of fluoride ions to vacancies (or the effective carrier concentration) was optimized in the “–Fβ(1)–Fβ(3)–Fβ(3)–Fβ(1)–” conduction pathways of fluoride ions in β-PbSnF4.
- Published
- 2017
32. Cubic Fluorite-Type CaH2 with a Small Bandgap
- Author
-
Toshiya Otomo, Sangwon Park, Hideo Hosono, Takashi Honda, Hiroshi Mizoguchi, and Kazutaka Ikeda
- Subjects
Alkaline earth metal ,business.industry ,Band gap ,Chemistry ,Hydride ,02 engineering and technology ,General Chemistry ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Crystallography ,Colloid and Surface Chemistry ,Semiconductor ,Density functional theory ,Orthorhombic crystal system ,0210 nano-technology ,business ,Electronic band structure - Abstract
A cubic variant of CaH2 adopting a fluorite-type crystal structure was synthesized by cationic substitution with La or Y, yielding the first alkaline earth hydride-based with fluorite-type framework. The material has a bandgap of ∼2.5 eV (greenish yellow in color), which is much smaller than that of orthorhombic PbCl2-type CaH2 (4.4 eV) and is, in fact, the smallest among alkaline or alkaline earth metal hydrides reported to date. Analysis of the density functional theory band structure of cubic-CaH2 indicates that its conduction band minimum is formed mainly by the interaction between the Ca 3d eg orbitals around the crystallographic cavity defined by cubes of H– ions. The use of such cavities in the creation of low-lying conduction band minima by semiconductors is extremely rare, and has similarities to inorganic electrides.
- Published
- 2017
33. Ferrimagnetic Cage Framework in Ca12Fe10Si4O32Cl6
- Author
-
Ryo Masuda, Soshi Iimura, Makoto Seto, Hideo Hosono, Yudai Tomota, Toshiya Otomo, Haruhiro Hiraka, Kazutaka Ikeda, and Satoru Matsuishi
- Subjects
Magnetic moment ,Magnetic structure ,Chemistry ,Oxide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,Transition metal ,Ferrimagnetism ,Mössbauer spectroscopy ,Tetrahedron ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The positively charged cage framework of the natural mineral mayenite, which enables various species with negative charge to be stabilized, is one of the key structures to provide the new functionalities exploited in applications. Here we report the structural and magnetic properties of recently found eltyubyuite, Ca12Fe10Si4O32Cl6, which is the first compound bearing a transition metal oxide as a main constituent in the mayenite-type structure. From neutron powder diffraction measurements at T = 20 K and the low temperature Mossbauer measurement, we determined the magnetic structure of eltyubyuite to be a ferrimagnet with oppositely aligned magnetic moments of +3.17(3) and −3.05(8) μB in two tetrahedral Fe sites with different oxygen ligands, all bridging oxygens or mixed bridging and nonbridging oxygens. As far as is known, this result is likely to be a first example showing ferrimagnetism stemming from only tetrahedral Fe3+ ions. The reduced magnetic moment per Fe3+ and the resultant small net moment p...
- Published
- 2016
34. Hydrogen-Release Reaction of a Complex Transition Metal Hydride with Covalently Bound Hydrogen and Hydride Ions
- Author
-
Toshiya Otomo, Kazutaka Ikeda, Anibal J. Ramirez-Cuesta, Shin Ichi Orimo, Luke L. Daemen, Toyoto Sato, Yongqiang Cheng, and Takuma Aoki
- Subjects
Materials science ,Hydrogen ,Hydride ,Neutron diffraction ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Isothermal process ,Inelastic neutron scattering ,0104 chemical sciences ,Ion ,chemistry ,Chemical bond ,Physical chemistry ,Transition metal hydride ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The hydrogen-release reaction of a complex transition metal hydride, LaMg2 NiH7 , composed of La3+ , 2×Mg2+ , [NiH4 ]4- and 3×H- , was studied by thermal analyses, powder X-ray, and neutron diffraction and inelastic neutron scattering. Upon heating, LaMg2 NiH7 released hydrogen at approximately 567 K and decomposed into LaH2-3 and Mg2 Ni. Before the reaction, covalently bound hydrogen (Hc °v. ) in [NiH4 ]4- exhibited a larger atomic displacement than H- , although a weakening of the chemical bonds around [NiH4 ]4- and H- was observed. These results indicate the precursor phenomenon of a hydrogen-release reaction, wherein there is a large atomic displacement of Hc °v. that induces the hydrogen-release reaction rather than H- . As an isothermal reaction, LaMg2 NiH7 formed LaMg2 NiH2.4 at 503 K in vacuum for 48 h, and LaMg2 NiH2.4 reacted with hydrogen to reform LaMg2 NiH7 at 473 K under 1 MPa of H2 gas pressure for 10 h. These results revealed that LaMg2 NiH7 exhibited partially reversible hydrogen-release and uptake reactions.
- Published
- 2018
35. Neutron total scattering used for the structure analysis of carbon materials
- Author
-
Kazutaka Ikeda and Toshiya Otomo
- Subjects
Materials science ,chemistry ,Structure analysis ,Scattering ,Analytical chemistry ,chemistry.chemical_element ,General Materials Science ,Neutron ,General Chemistry ,Carbon - Published
- 2021
36. Zirconium hydride-stabilized yttrium hydride (ZSY): Stabilization of a face-centered cubic YH3 phase by Zr substitution
- Author
-
Nobuhiko Takeichi, Toru Kimura, Kazutaka Ikeda, Riki Kataoka, Atsunori Kamegawa, Kouji Sakaki, Masashi Nozaki, Toshikatsu Kojima, and Toshiya Otomo
- Subjects
Zirconium ,Materials science ,Hydrogen ,Mechanical Engineering ,Metals and Alloys ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Yttrium ,Zirconium hydride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Mole fraction ,01 natural sciences ,0104 chemical sciences ,Hydrogen storage ,Lattice constant ,chemistry ,Mechanics of Materials ,Materials Chemistry ,Dehydrogenation ,0210 nano-technology - Abstract
Yttrium in YH3 was shown to be substituted by zirconium in a ball milling process, yielding FCC-YH3, a zirconium-hydride-stabilized YH3 (ZSY) structure. FCC-YH3, which is stable only under the pressure greater than 7.8 GPa, has previously been reported to be stabilized at ambient pressure by alkaline or alkaline earth metal substitution, but only in a limited compositional range. In contrast, we demonstrated solid solubility of Y and Zr in ZSY in a wide compositional range, with a Y/Zr molar ratio between 4 and 0.333, as confirmed by changes in the lattice constants of ZSY with various amounts of Zr. A color of ZSY changed from yellowish (transparent) to black by Zr substitution. The UV–vis spectroscopy revealed that Zr substitution narrowed the bandgap of YH3. At a molar fraction of 33 mol%, Zr-substituted ZSY was shown to maintain its FCC structure during dehydrogenation and rehydrogenation cyclirng, and its volume change ( Δ V ) was estimated to be 1%, with an accompanying H2 emission of 0.5 wt%. This volume change was significantly lower than that of conventional hydrogen storage alloys such as LaNi5 and Mg–La–Ni alloys, i.e., Δ V is about 10 ∼ 20% when they desorb same amount of hydrogen.
- Published
- 2021
37. Strain-induced creation and switching of anion vacancy layers in perovskite oxynitrides
- Author
-
Masatomo Yashima, Takao Mori, Shunsaku Kitagawa, Wenhao Sun, Takahiro Maruyama, Kotaro Fujii, Takashi Honda, Toshiya Otomo, Akira Chikamatsu, Shunsuke Yamashita, Kazutaka Ikeda, Koji Kimoto, Masayuki Ochi, Masahito Sano, Kenji Ishida, Tetsuya Hasegawa, Daiichiro Sekiba, Yasushi Hirose, Fumitaka Takeiri, Hiroshi Takatsu, Kazuhiko Kuroki, Nana Izumo, Craig M. Brown, Morito Namba, Yuki Sugisawa, Hiroshi Kageyama, Takahide Nakashima, and Takafumi Yamamoto
- Subjects
Materials science ,Electronic materials ,Science ,Superlattice ,Oxide ,General Physics and Astronomy ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,Epitaxy ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,chemistry.chemical_compound ,Vacancy defect ,Thin film ,Perovskite (structure) ,Multidisciplinary ,Heterojunction ,Solid-state chemistry ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical physics ,0210 nano-technology - Abstract
Perovskite oxides can host various anion-vacancy orders, which greatly change their properties, but the order pattern is still difficult to manipulate. Separately, lattice strain between thin film oxides and a substrate induces improved functions and novel states of matter, while little attention has been paid to changes in chemical composition. Here we combine these two aspects to achieve strain-induced creation and switching of anion-vacancy patterns in perovskite films. Epitaxial SrVO3 films are topochemically converted to anion-deficient oxynitrides by ammonia treatment, where the direction or periodicity of defect planes is altered depending on the substrate employed, unlike the known change in crystal orientation. First-principles calculations verified its biaxial strain effect. Like oxide heterostructures, the oxynitride has a superlattice of insulating and metallic blocks. Given the abundance of perovskite families, this study provides new opportunities to design superlattices by chemically modifying simple perovskite oxides with tunable anion-vacancy patterns through epitaxial lattice strain., Using strain to control oxynitride properties. 京都大学プレスリリース. 2020-12-01., 原子空孔の配列を制御する新手法の発見. 京都大学プレスリリース. 2020-12-02.
- Published
- 2020
38. Nanometer-Size Effect on Hydrogen Sites in Palladium Lattice
- Author
-
Maiko Kofu, Hiroshi Akiba, Osamu Yamamuro, Hirokazu Kobayashi, Toshiya Otomo, Hiroshi Kitagawa, and Kazutaka Ikeda
- Subjects
Hydrogen ,Hydride ,Rietveld refinement ,chemistry.chemical_element ,Palladium hydride ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,chemistry ,Octahedron ,Nanocrystal ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology ,Palladium - Abstract
Nanometer-sized materials attract much attention because their physical and chemical properties are substantially different from those of bulk materials owing to their size and surface effects. In this work, neutron powder diffraction experiments on the nanoparticles of palladium hydride, which is the most popular metal hydride, have been performed at 300, 150, and 44 K to investigate the positions of the hydrogen atoms in the face-centered cubic (fcc) lattice of palladium. We used high-quality PdD0.363 nanocrystals with a diameter of 8.0 ± 0.9 nm. The Rietveld analysis revealed that 30% of D atoms are located at the tetrahedral (T) sites and 70% at the octahedral (O) sites. In contrast, only the O sites are occupied in bulk palladium hydride and in most fcc metal hydrides. The temperature dependence of the T-site occupancy suggested that the T-sites are occupied only in a limited part, probably in the subsurface region, of the nanoparticles. This is the first study to determine the hydrogen sites in metal nanoparticles.
- Published
- 2016
39. Microscopic Structure of Contact Ion Pairs in Concentrated LiCl- and LiClO4-Tetrahydrofuran Solutions Studied by Low-Frequency Isotropic Raman Scattering and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods
- Author
-
Yasuo Kameda, Yuko Amo, Saki Ebina, Toshiya Otomo, and Takeshi Usuki
- Subjects
Chemistry ,Neutron diffraction ,Isotropy ,Analytical chemistry ,02 engineering and technology ,Low frequency ,Ion pairs ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Difference function ,symbols.namesake ,Crystallography ,Materials Chemistry ,symbols ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tetrahydrofuran ,Raman scattering - Abstract
Low-frequency isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for (6)Li/(7)Li and H/D isotopically substituted *LiCl- and *LiClO4-tetrahydrofuran (*THF) solutions in order to obtain microscopic insight into solvated Li(+), Li(+)···Cl(-) and Li(+)···ClO4(-) contact ion pairs formed in concentrated THF solutions. Symmetrical stretching vibrational mode of solvated Li(+) in LiCl and LiClO4 solutions was observed at ν = 181-184 and 140 cm(-1), respectively. The stretching vibrational mode of Li(+)···Cl(-) and Li(+)···ClO4(-) solvated contact ion pairs formed in 4 mol % (6)LiCl-THF-h8 and (7)LiCl-THF-h8 solutions was found at ν = 469 and 435 cm(-1), respectively. Detailed structural properties of solvated Li(+) and the contact ion pairs were derived from the least-squares fitting analyses of the first-order difference function, ΔLi(Q), obtained from neutron diffraction measurements on (6)Li/(7)Li isotopically substituted THF-d8 solutions. It has been revealed that Li(+) takes 4-fold coordination in the average local structure of Li(+)X(-)(THF)3, X = Cl and ClO4. The nearest neighbor Li(+)···O(THF) distance was determined to be 2.21 ± 0.01 Å and 2.07 ± 0.01 Å for 4 mol % *LiCl- and 10 mol % *LiClO4-THF-d8 solutions, respectively. The Li(+)···anion distances for Li(+)···Cl(-) and Li(+)···O(ClO4(-)) contact ion pairs were determined to be 2.4 ± 0.1 Å and 2.19 ± 0.01 Å, respectively. The nearest neighbor Li(+)···THF interaction is significantly modified by the anion in the first solvation shell.
- Published
- 2016
40. Metallic Intermediate Hydride Phase of LaMg2Ni with Ni–H Covalent Bonding: Precursor State for Complex Hydride Formation
- Author
-
Motoaki Matsuo, Kazutoshi Miwa, Kazutaka Ikeda, Shigeyuki Takagi, Toyoto Sato, Bjørn C. Hauback, Toshiya Otomo, Shin Ichi Orimo, Guanqiao Li, and Stefano Deledda
- Subjects
Chemistry ,Hydride ,Intermetallic ,02 engineering and technology ,Electronic structure ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,General Energy ,Covalent bond ,Phase (matter) ,visual_art ,0103 physical sciences ,Hydrogenation reaction ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology ,Ternary operation - Abstract
An intermediate phase LaMg2NiH4.6 found for the hydrogenation reaction of the ternary intermetallic compound LaMg2Ni to the complex transition-metal hydride LaMg2NiH7 has been investigated experimentally and theoretically. It is known that this reaction induces only minor rearrangement of the host metal atoms, and this feature is also observed for the intermediate compound. Another important feature is that the electronic structure of the intermediate phase is metallic, which is free from the energy barrier associated with the metal–insulator transition. The hydrogenation reaction to the intermediate phase proceeds even at room temperature, when the Ni–H clusters are formed. The internal bonding of the Ni–H clusters has a covalent nature, the same as those of NiH4 complexes in LaMg2NiH7. They most likely play as the precursor states for the following complex hydride formation. This picture is insightful to enhance the formation of complex hydrides.
- Published
- 2016
41. Structural Studies of Hydrogen Storage Materials with Neutron Diffraction: A Review
- Author
-
Toshiya Otomo, Kazutaka Ikeda, and Takashi Honda
- Subjects
Hydrogen storage ,Materials science ,Hydrogen ,chemistry ,Desorption ,Neutron diffraction ,General Physics and Astronomy ,chemistry.chemical_element ,Physical chemistry ,Neutron ,Physics::Atomic Physics ,Hydrogen absorption - Abstract
To understand hydrogen absorption and desorption properties and to design hydrogen storage materials, structural information (especially, hydrogen position information) is fundamental. Neutron diff...
- Published
- 2020
42. Structural and electrochemical features of (Li2S) (SiS2)100– superionic glasses
- Author
-
Kazutaka Ikeda, Toshiharu Fukunaga, Kazuhiro Mori, Yojiro Oba, Toshiya Otomo, and Kenji Iwase
- Subjects
Diffraction ,Valence (chemistry) ,Materials science ,Silicon ,Neutron diffraction ,Analytical chemistry ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Reverse Monte Carlo ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Ion ,chemistry ,Fast ion conductor ,General Materials Science ,0210 nano-technology - Abstract
Silicon is easily available and thus its use in solid electrolytes in all-solid-state lithium-ion batteries can reduce the cost of the system. Thus, significant research attention is focused on (Li2S)x(SiS2)100−x glasses as solid electrolytes because they exhibit the highest ionic conductivities among Li ion conducting glasses. However, there is a paucity of details on how Li ions actually travel through an operating device. In the present work, four-probe AC impedance measurements, synchrotron X-ray diffraction experiments, and time-of-flight neutron diffraction experiments were performed using 7Li-enriched (7Li2S)x(SiS2)100−x glasses (x = 40, 50, and 60). We demonstrated the three-dimensional atomic configurations and conduction pathways of Li ions for (7Li2S)x(SiS2)100−x glasses via reverse Monte Carlo (RMC) modeling and bond valence sum (BVS) imaging. Specifically, BVS imaging indicated that the frameworks of the (Li2S)x(SiS2)100−x glasses facilitate high mobility of the conducting Li ions when compared with those of (Li2S)x(GeS2)100−x glasses and (Li2S)x(P2S5)100−x glasses.
- Published
- 2020
43. Elastic and dynamical structural properties of La and Mn-doped SrTiO3 studied by neutron scattering and their relation with thermal conductivities
- Author
-
Takahiro Eto, Mitsutaka Nakamura, Hiroto Hata, Masaaki Noda, Takashi Honda, Naoki Murai, Toshiya Otomo, Hideki Kuwahara, Shin-ichi Shamoto, Kazutaka Ikeda, Ryoichi Kajimoto, and Tetsuji Okuda
- Subjects
Materials science ,Oxide ,lcsh:Medicine ,02 engineering and technology ,Inelastic scattering ,Neutron scattering ,01 natural sciences ,Ion ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Thermal conductivity ,Condensed Matter::Superconductivity ,0103 physical sciences ,Thermoelectric effect ,lcsh:Science ,010306 general physics ,Multidisciplinary ,Condensed matter physics ,lcsh:R ,Doping ,021001 nanoscience & nanotechnology ,Ferroelectricity ,chemistry ,lcsh:Q ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
The electron-doped SrTiO3 exhibits good thermoelectric properties, which makes this material a promising candidate of an n-type oxide thermoelectric device. Recent studies indicated that only a few percent co-doping of La and Mn in SrTiO3 substantially reduces the thermal conductivity, thereby greatly improving the thermoelectric figure of merit at room temperature. Our time-of-flight neutron scattering studies revealed that by doping both La and Mn into SrTiO3, the inelastic scattering spectrum shows a momentum-independent increase in the low-energy spectral weight approximately below 10 meV. The increase in the low-energy spectral weight exhibits a clear correlation with thermal conductivity. The correlation is attributed to dynamical and local structural fluctuations caused by the Jahn-Teller instability in Mn3+ ions coupled with the incipient ferroelectric nature of SrTiO3, as the origin of the low thermal conductivity.
- Published
- 2018
44. True Boundary for the Formation of Homoleptic Transition-Metal Hydride Complexes
- Author
-
Kazutaka Ikeda, Toyoto Sato, Katsutoshi Aoki, Kazutoshi Miwa, Shin Ichi Orimo, Tamio Ikeshoji, Shigeyuki Takagi, Hiroyuki Saitoh, Yuki Iijima, and Toshiya Otomo
- Subjects
Hydride ,Chemistry ,Coordination number ,Neutron diffraction ,Inorganic chemistry ,Ionic bonding ,General Medicine ,General Chemistry ,Catalysis ,Crystallography ,chemistry.chemical_compound ,Transition metal ,Metal carbonyl hydride ,Transition metal hydride ,Homoleptic - Abstract
Despite many exploratory studies over the past several decades, the presently known transition metals that form homoleptic transition-metal hydride complexes are limited to the Groups 7-12. Here we present evidence for the formation of Mg3 CrH8 , containing the first Group 6 hydride complex [CrH7 ](5-) . Our theoretical calculations reveal that pentagonal-bipyramidal H coordination allows the formation of σ-bonds between H and Cr. The results are strongly supported by neutron diffraction and IR spectroscopic measurements. Given that the Group 3-5 elements favor ionic/metallic bonding with H, along with the current results, the true boundary for the formation of homoleptic transition-metal hydride complexes should be between Group 5 and 6. As the H coordination number generally tends to increase with decreasing atomic number of transition metals, the revised boundary suggests high potential for further discovery of hydrogen-rich materials that are of both technological and fundamental interest.
- Published
- 2015
45. Analysis of Prepeak Structure of Concentrated Organic Lithium Electrolyte by Means of Neutron Diffraction with Isotopic Substitution and Molecular Dynamics Simulation
- Author
-
Tsuyoshi Yamaguchi, Toshiya Otomo, Kazutaka Ikeda, Toshio Yamaguchi, Koji Yoshida, and Yasuo Kameda
- Subjects
Isotope ,Chemistry ,Neutron diffraction ,Analytical chemistry ,Ionic bonding ,Scattering length ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Solvent ,Molecular dynamics ,Crystallography ,chemistry.chemical_compound ,Propylene carbonate ,Materials Chemistry ,Physical and Theoretical Chemistry ,0210 nano-technology ,Lithium atom - Abstract
The prepeak structure of a 3 mol/kg solution of LiClO4 in propylene carbonate (PC) was studied by both neutron diffraction with isotopic substitution (NDIS) and molecular dynamics (MD) simulation. The NDIS data showed that the intensity of the prepeak decreases experimentally with an increase in the scattering length of the lithium atom from 7Li to 6Li in PC-d6. On the other hand, although the prepeak was observed in solutions of both PC-d6 and PC-h6, it disappears when the 1:1 mixture of PC-d6 and PC-h6 was used as the solvent. The prepeak structure and its variation with the isotope substitution were reproduced well by MD simulation, and they were explained in terms of the contrast of the scattering length densities of the ionic and nonpolar domains.
- Published
- 2017
46. Formation of novel transition metal hydride complexes with ninefold hydrogen coordination
- Author
-
Shigeyuki Takagi, Kazutaka Ikeda, Kazutoshi Miwa, Hiroyuki Saitoh, Tamio Ikeshoji, Toshiya Otomo, Yuki Iijima, Shin Ichi Orimo, and Toyoto Sato
- Subjects
Multidisciplinary ,Materials science ,Hydrogen ,Hydride ,Band gap ,Tantalum ,chemistry.chemical_element ,02 engineering and technology ,Rhenium ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Article ,0104 chemical sciences ,Crystallography ,chemistry ,Metal carbonyl hydride ,Transition metal hydride ,Lithium ,0210 nano-technology - Abstract
Ninefold coordination of hydrogen is very rare, and has been observed in two different hydride complexes comprising rhenium and technetium. Herein, based on a theoretical/experimental approach, we present evidence for the formation of ninefold H- coordination hydride complexes of molybdenum ([MoH9]3−), tungsten ([WH9]3−), niobium ([NbH9]4−) and tantalum ([TaH9]4−) in novel complex transition-metal hydrides, Li5MoH11, Li5WH11, Li6NbH11 and Li6TaH11, respectively. All of the synthesized materials are insulated with band gaps of approximately 4 eV, but contain a sufficient amount of hydrogen to cause the H 1s-derived states to reach the Fermi level. Such hydrogen-rich materials might be of interest for high-critical-temperature superconductivity if the gaps close under compression. Furthermore, the hydride complexes exhibit significant rotational motions associated with anharmonic librations at room temperature, which are often discussed in relation to the translational diffusion of cations in alkali-metal dodecahydro-closo-dodecaborates and strongly point to the emergence of a fast lithium conduction even at room temperature.
- Published
- 2017
47. In-situ powder neutron diffraction study on the formation process of LaMg2NiH7
- Author
-
Shigeyuki Takagi, Stefano Deledda, Bjørn C. Hauback, Guanqiao Li, Toshiya Otomo, Motoaki Matsuo, Shin Ichi Orimo, Toyoto Sato, Kazutaka Ikeda, and Kazutoshi Miwa
- Subjects
In situ ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Hydride ,Neutron diffraction ,Analytical chemistry ,Intermetallic ,Energy Engineering and Power Technology ,Bragg peak ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Crystallography ,Fuel Technology ,Deuterium ,Lattice (order) ,0210 nano-technology - Abstract
The formation process from the intermetallic compound LaMg2Ni to a complex hydride (deuteride) LaMg2NiD7 composed of La3+, 2 × Mg2+, [NiD4]4−, and 3 × D− was investigated by in-situ powder neutron diffraction under deuterium gas pressure at room temperature. Below 0.001 MPa, small amount of deuterium was initially dissolved in the lattice of LaMg2Ni forming LaMg2NiD0.05 and two new hydride phases (LaMg2NiDx1 and LaMg2NiDx2) were continuously yielded. Furthermore, LaMg2NiD4.6 with NiD1.9 and NiD3.3 units and interstitial deuterium atoms was formed prior to appearing of LaMg2NiD7. From their Bragg peak positions, the deuterium contents x1, and x2 were inferred as 0.05
- Published
- 2017
48. Neutron Diffraction Study on the Structure of Aqueous LiNO3 Solutions
- Author
-
Takeshi Usuki, Takuya Miyazaki, Yasuo Kameda, Toshiya Otomo, and Yuko Amo
- Subjects
Heavy water ,Aqueous solution ,Chemistry ,Scattering ,Coordination number ,Intermolecular force ,Neutron diffraction ,Biophysics ,Analytical chemistry ,Biochemistry ,Ion ,k-nearest neighbors algorithm ,chemistry.chemical_compound ,Crystallography ,Physical and Theoretical Chemistry ,Molecular Biology - Abstract
Neutron diffraction measurements were carried out at 25 °C for aqueous LiNO3 heavy water solutions, (*LiNO3) x (D2O)1−x where x = 0.1, 0.05 and 0.01, in which the 6Li/7Li isotopic ratios were varied. Structural information on intermolecular nearest neighbor Li+···D2O interactions in the extensive concentration range was derived from the first-order difference function, ∆Li(Q), obtained from the difference in scattering cross sections between 6Li- and 7Li-enriched sample solutions. The nearest neighbor Li+···O distance and coordination number for sample solution with x = 0.1 were determined to be r LiO = 1.969 (8) A and n LiO = 4.12 (6), respectively, corresponding to the four-coordinated Li+ ion in the solution. On the other hand, those obtained for the solution with x = 0.01 are r LiO = 2.00 (2) A and n LiO = 6.0 (2), respectively, indicating that hexaaqua Li+ is dominant in the dilute solution. These results clearly indicate that a concentration dependence of the hydration number of Li+ occurs in the aqueous solutions.
- Published
- 2014
49. Hydrogen Ordering and New Polymorph of Layered Perovskite Oxyhydrides: Sr2VO4–xHx
- Author
-
Joonho Bang, Jun-ichi Yamaura, Hideo Hosono, Reiji Kumai, Satoru Matsuishi, Youichi Murakami, Haruhiro Hiraka, Toshiya Otomo, Sachiko Maki, and Fumika Fujisaki
- Subjects
Chemical Physics (physics.chem-ph) ,Condensed Matter - Materials Science ,Strongly Correlated Electrons (cond-mat.str-el) ,Hydrogen ,Thermal desorption spectroscopy ,Neutron diffraction ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Vanadium ,chemistry.chemical_element ,General Chemistry ,Biochemistry ,Catalysis ,Condensed Matter - Strongly Correlated Electrons ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,chemistry ,Physics - Chemical Physics ,Vacancy defect ,Density functional theory ,Hydrogen anion ,Perovskite (structure) - Abstract
Compositionally tunable vanadium oxyhydrides Sr2VO4-xHx (x = 0 - 1) without considerable anion vacancy were synthesized by high-pressure solid state reaction. The crystal structures and their properties were characterized by powder neutron diffraction, synchrotron X-ray diffraction, thermal desorption spectroscopy, and first-principles density functional theory (DFT) calculations. The hydrogen anions selectively replaced equatorial oxygen sites in the VO6 layers via statistical substitution of hydrogen in the low x region (x < 0.2). A new orthorhombic phase (Immm) with an almost entirely hydrogen-ordered structure formed from the K2NiF4-type tetragonal phase with x > 0.7. Based on the DFT calculations, the degree of oxygen/hydrogen anion ordering is strongly correlated with the bonding interaction between vanadium and the ligands., 19 pages, 5 figures
- Published
- 2014
50. Magnetic Structure and Electromagnetic Properties of LnCrAsO witha ZrCuSiAs-type Structure (Ln = La, Ce, Pr, and Nd)
- Author
-
Hiroshi Mizoguchi, Sangwon Park, Shin-ichi Shamoto, Toshio Kamiya, Katsuaki Kodama, Hideo Hosono, Toshiya Otomo, and Satoru Matsuishi
- Subjects
Inorganic Chemistry ,Condensed matter physics ,Magnetic structure ,Chemistry ,Neutron diffraction ,Antiferromagnetism ,Density functional theory ,Electronic structure ,Crystal structure ,Physical and Theoretical Chemistry ,Magnetic susceptibility ,Spin-½ - Abstract
We report the synthesis, structure, and electromagnetic properties of Cr-based layered oxyarsenides LnCrAsO (Ln = La, Ce, Pr, and Nd) with a ZrCuSiAs-type structure. All LnCrAsO samples showed metallic electronic conduction. Electron doping in LaCrAsO by Mn-substitution for the Cr sites gave rise to a metal-insulator transition. Analysis of powder neutron diffraction data revealed that LaCrAsO had G-type antiferromagnetic (AFM) ordering, i.e., a checkerboard-type AFM ordering in the CrAs plane and antiparallel spin coupling between the adjacent CrAs planes, at 300 K with a large spin moment of 1.57 μB along the c axis. The magnetic susceptibility of LaCrAsO was very small (on the order of 10(-3) emu/mol) and showed a broad hump at ∼550 K. First-principles density functional theory calculations of LaCrAsO explained its crystal structure and metallic nature well, but could not replicate the antiparallel spin coupling between the CrAs layers. The electronic structure of LaCrAsO is discussed with regard to those of related compounds LaFeAsO and LaMnAsO.
- Published
- 2013
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.