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Journal Articles

Local disorder in proton conductor BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ analyzed by neutron diffraction/ atomic pair distribution function

Igawa, Naoki; Kodama, Katsuaki; Taguchi, Tomitsugu*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*

Transactions of the Materials Research Society of Japan, 43(6), p.329 - 332, 2018/12

For the understanding of the crystal structural effect on the electrical properties, the local disorder in BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ which is one of the excellent proton conductors for solid oxide fuel cells was estimated by using the Atomic Pair Distribution Function (PDF) analysis method with the neutron diffraction. The local structure is almost the same as the average structure which was estimated by the Rietveld analysis using the cubic crystal structure (space group, $${it Pm}$$$$overline{3}$$$${it m}$$) in the atomic distance range of ${it r}$ $$>$$ 6${AA}$. The PDF profile was fitted better using the tetragonal crystal structure with the space group of ${it P}$4/${it mmm}$ than those with $${it Pm}$$$$overline{3}$$$${it m}$$ in the range ${it r}$ $$<$$ 6${AA}$. Those results indicate the presence of the local disorder in the lattice. In this work, the relationship between the average and local structures of BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ will be discussed.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Time-of-flight elastic and inelastic neutron scattering studies on the localized 4d electron layered perovskite La$$_5$$Mo$$_4$$O$$_{16}$$

Iida, Kazuki*; Kajimoto, Ryoichi; Mizuno, Yusuke*; Kamazawa, Kazuya*; Inamura, Yasuhiro; Hoshikawa, Akinori*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Ishigaki, Toru*; Kawamura, Yukihiko*; et al.

Journal of the Physical Society of Japan, 86(6), p.064803_1 - 064803_6, 2017/06

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Rapid measurement scheme for texture in cubic metallic materials using time-of-flight neutron diffraction at iMATERIA

Onuki, Yusuke*; Hoshikawa, Akinori*; Sato, Shigeo*; Xu, P. G.; Ishigaki, Toru*; Saito, Yoichi*; Todoroki, Hidekazu*; Hayashi, Makoto*

Journal of Applied Crystallography, 49(5), p.1579 - 1584, 2016/10


 Times Cited Count:15 Percentile:15.06(Chemistry, Multidisciplinary)

Journal Articles

Local lattice distortion caused by short-range charge ordering in transition metal oxides

Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Ikeda, Kazutaka*; Oshita, Hidetoshi*; Kaneko, Naokatsu*; Otomo, Toshiya*; Suzuya, Kentaro; Hoshikawa, Akinori*; Ishigaki, Toru*

JPS Conference Proceedings (Internet), 8, p.034002_1 - 034002_6, 2015/09

Journal Articles

Development of bulk texture measurement technique by time-of-flight neutron diffraction

Xu, P. G.; Hoshikawa, Akinori*; Hayashi, Makoto*; Akita, Koichi; Morii, Yukio*; Ishigaki, Toru*

Nippon Zairyo Gakkai Dai-48-Kai X Sen Zairyo Kyodo Ni Kansuru Shimpojiumu Koen Rombunshu, p.7 - 9, 2014/07

Journal Articles

Local structural analysis by using atomic pair distribution function on mixed valence compound LiMn$$_2$$O$$_4$$

Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Ikeda, Kazutaka*; Oshita, Hidetoshi*; Kaneko, Naokatsu*; Otomo, Toshiya*; Suzuya, Kentaro; Hoshikawa, Akinori*; Ishigaki, Toru*

JPS Conference Proceedings (Internet), 3, p.013012_1 - 013012_6, 2014/06

Journal Articles

Spin state of Co$$^{3+} $$ in LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ investigated by structural phenomena

Asai, Shinichiro*; Okazaki, Ryuji*; Terasaki, Ichiro*; Yasui, Yukio*; Kobayashi, Wataru*; Nakao, Akiko*; Kobayashi, Kensuke*; Kumai, Reiji*; Nakao, Hironori*; Murakami, Yoichi*; et al.

Journal of the Physical Society of Japan, 82(11), p.114606_1 - 114606_6, 2013/11

 Times Cited Count:6 Percentile:50.55(Physics, Multidisciplinary)

Neutron and synchrotron X-ray diffraction for LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ have been carried out in order to investigate the structural properties related with the spin state of Co$$^{3+}$$ ions. We have found that the values of the Co(Rh)-O bond lengths in the Co(Rh)O$$_{6}$$ octahedron of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$ are nearly identical at 10 K. The lattice volume for the Rh$$^{3+}$$ substituted samples decreases with the thermal expansion coefficient similar to that of LaCoO$$_{3}$$ from room temperature, and ceases to decrease around 70 K. These experimental results favor a mixed state consisting of the high-spin state and low-spin state Co$$^{3+}$$ ions, and suggest that the high-spin state Co$$^{3+}$$ ions are thermally excited in addition to those pinned by the substituted Rh$$^{3+}$$ ions.

Journal Articles

Neutron diffraction study on the Xe behavior in clathrate hydrate analyzed by Rietveld/maximum entropy method

Igawa, Naoki; Taguchi, Tomitsugu; Hoshikawa, Akinori*; Yamauchi, Hiroki; Birumachi, Atsushi; Ishii, Yoshinobu*

IOP Conference Series; Materials Science and Engineering, 18, p.022021_1 - 022021_4, 2011/05

The neutron scattering length density distributions of Xe deuterohydrate were analyzed by Rietveld and MEM analysis applied to neutron powder diffraction data to clarify the Xe behavior in the temperature range from 10 to 245 K. A spherical positive scattering length density attributed to the Xe atom was observed at the center of the small cage of the hydrate. On the other hand, an ellipsoid shaped scattering length density distribution at the center of the large cage was observed; the major axis of the ellipsoid scattering length density was directed toward the center of a hexagonal facet of the large cage. The distributions of the Xe atom in the both cages were almost the same at any temperature.

Journal Articles

Low temperature structure of FeSr$$_{2}$$YCu$$_{2}$$O$$_{6+delta}$$ magnetic superconductor

Mochiku, Takashi*; Hata, Yoshiaki*; Wuernisha, T.*; Igawa, Naoki; Hoshikawa, Akinori*; Ishigaki, Toru*; Yasuoka, Hiroshi*; Hirata, Kazuto*

Physica C, 470(Suppl.1), p.S158 - S159, 2010/12

 Times Cited Count:2 Percentile:86.24(Physics, Applied)

We have performed neutron powder diffraction of the superconducting FeSr$$_{2}$$YCu$$_{2}$$O$$_{6+}$$$$_{delta}$$ and the nonsuperconducting FeSr$$_{2}$$Y(Cu$$_{0.95}$$Zn$$_{0.05}$$)$$_{2}$$O$$_{6+}$$$$_{delta}$$ samples at low temperature and room temperature to investigate the relation between the crystal structure ant the physical properties. Neutron diffraction study indicates that the magnetic order in this compound is not long-range order because we observed no extra reflection due to the magnetic superstructure. We have observed structural anomaly related to Cu in the superconducting sample around 30 K although we could not observe it in the nonsuperconducting sample. There is possibility of the change of the charge distribution around 30 K in the superconducting sample.

Journal Articles

CO$$_{2}$$ motion in carbon dioxide deuterohydrate determined by applying maximum entropy method to neutron powder diffraction data

Igawa, Naoki; Taguchi, Tomitsugu; Hoshikawa, Akinori*; Fukazawa, Hiroshi; Yamauchi, Hiroki; Utsumi, Wataru; Ishii, Yoshinobu*

Journal of Physics and Chemistry of Solids, 71(6), p.899 - 905, 2010/06

 Times Cited Count:6 Percentile:66.13(Chemistry, Multidisciplinary)

Crystal structures of carbon dioxide deuterohydrate were studied by neutron powder diffraction at temperatures from 10 to 200 K. Maps of scattering length density distribution were obtained using a maximum entropy method, which clarified the motion of CO$$_{2}$$ molecules in the hydrate. In small cages, the carbon atom of the CO$$_{2}$$ molecule is at the center of the cage, and the oxygen atoms of CO$$_{2}$$ revolve freely around the carbon atom. In large cages, the carbon atom also is at the center of the cage, but the oxygen atoms tend to revolve around the carbon atom along the plane parallel to the hexagonal facets of the cage.

Journal Articles

Existence of ferroelectric ice on planets; A Neutron diffraction study

Fukazawa, Hiroshi; Hoshikawa, Akinori*; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*

Nuclear Instruments and Methods in Physics Research A, 600(1), p.279 - 281, 2009/02

 Times Cited Count:12 Percentile:32.29(Instruments & Instrumentation)

We measured time-resolved neutron powder diffraction of ices doped with very small amounts of some catalysts using the wide-angle neutron diffractometer (WAND) at the High Flax Isotope Reactor (HFIR) in Oak Ridge, Tennessee. We succeeded in making ferroelectric ice, which prepared at high pressures (0.2 and 0.4 GPa), in a 60 to 75 K temperature range over tens hours. Neutron diffraction experiments confirmed the existence of a large ferroelectric structure in the sample. Therefore, thick surface (about 500 Km) of ferroelectric ice may exist on cold icy bodies, such as, Pluto and Kuiper Belt Objects (KBO). It suggests that about 70% of Pluto body is ferroelectric ice. Future telescope or planetary probe will be able to detect the huge ferroelectric-ice mass. In this symposium we report recent results at the HFIR and our future plan using higher intensity neutron beam.

Journal Articles

Observation of hydrogen in methane hydrate by neutron powder diffraction

Hoshikawa, Akinori

Nippon Kessho Gakkai-Shi, 49(4), p.219 - 224, 2007/08

no abstracts in English

Journal Articles

Magnetic structural characterization of Mg-Co-Cr ferrite by neutron diffraction

Yunus, S. M.*; Yamauchi, Hiroki; Zakaria, A. K. M.*; Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu

Journal of Magnetism and Magnetic Materials, 310(2, Part3), p.2722 - 2724, 2007/03

 Times Cited Count:2 Percentile:86.36(Materials Science, Multidisciplinary)

Temperature dependent neutron diffraction studies were done on the spinel oxide system Mg$$_x$$Co$$_{1-x}$$Cr$$_x$$Fe$$_{2-x}$$O$$_4$$ ($$x=0.0$$, 0.25, 0.50, 0.75 and 1.0). Neutron diffraction data recorded in the temperature range 10,$$-$$,810 K were analyzed in the Rietveld method. Ordered sublattice magnetic moments of the five compositions of the spinel series at various temperatures were deduced from the analysis. A decreasing ordered moment with increasing substitution ($$x$$) was found indicating a gradual weakening of ferrimagnetic order. Huge diffuse signals around the 1,1,1 Bragg diffraction peak were found in the neutron patterns of the composition $$x$$,=,1.0 below the Curie temperature manifesting a build-up of short-range magnetic spin clusters. The observed features suggest a canted ferrimagnetic structure in the composition range $$x$$,$$leq$$,0.75 and a semi-spin glass like transition at $$x$$,=,1.0.

Journal Articles

Existence of ferroelectric ice in the universe

Fukazawa, Hiroshi; Hoshikawa, Akinori; Ishii, Yoshinobu; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*

Astrophysical Journal, 652(1, Part2), p.L57 - L60, 2006/11

 Times Cited Count:39 Percentile:29.29(Astronomy & Astrophysics)

Whether ferroelectric ice, named ice XI, exists in a stable low-temperature phase attracts much interest. This question arose as a condensed-matter issue, and became of interest in astronomy (e.g., does ice XI exist on Pluto?) because astronomical observations identified the existence of crystalline ice in our solar system. From neutron diffraction experiments, we found the temperature conditions for the transformation of the largest fraction of ice into ice XI using the lowest level of impurity dopant. The finding of bulk crystal of ordered structure firmly supports that ice XI is stable. This suggests the existence of naturally occurring ice XI at a narrow temperature range (57-66 K) in our solar system.

Journal Articles

Deuteron ordering in ice containing impurities; A Neutron diffraction study

Fukazawa, Hiroshi; Hoshikawa, Akinori; Yamauchi, Hiroki; Yamaguchi, Yasuo*; Igawa, Naoki; Ishii, Yoshinobu

Physica B; Condensed Matter, 385-386(1), p.113 - 115, 2006/11

 Times Cited Count:3 Percentile:80.71(Physics, Condensed Matter)

We measured neutron diffraction of powdered samples of ice containing impurities (e.g., potassium deuteroxide, sodium deuteroxide) to analyze the formation of ice XI, a deuterium-ordered phase of ice, from ice Ih, a disordered phase. We found that the diffraction profiles changed with time for several days at 62-70 K, which are below the transition temperature $$T$$$$_{rm c}$$ = 76 K. From the Rietveld analysis of the diffraction profiles, we determined the change of the structural parameters with the phase transition. The structural analysis provides direct evidence for the existence of deuteron-ordered arrangements in ice containing impurities below $$T$$$$_{rm c}$$. On the basis of the Rietveld analysis, we obtained the mass fraction ($$f$$) of ice XI as functions of time and temperature. We report a structural observation for the nucleation and growth of ice XI under various conditions (such as temperature variations and impurity effects), which leads to understand whether or not f reaches unity at an infinite annealing time.

Journal Articles

Observation of hydrogen in deuterated methane hydrate by maximum entropy method with neutron powder diffraction

Hoshikawa, Akinori; Igawa, Naoki; Yamauchi, Hiroki; Ishii, Yoshinobu

Journal of Chemical Physics, 125(3), p.034505_1 - 034505_6, 2006/07

 Times Cited Count:11 Percentile:61.34(Chemistry, Physical)

no abstracts in English

Journal Articles

Precise structural analysis of methane hydrate by neutron diffraction

Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu

Hamon, 16(2), p.116 - 119, 2006/04

no abstracts in English

Journal Articles

Neutron powder diffraction study of methane deuterohydrate by the maximum entropy method

Hoshikawa, Akinori; Igawa, Naoki; Yamauchi, Hiroki; Ishii, Yoshinobu

Journal of Physics and Chemistry of Solids, 66(10), p.1810 - 1814, 2005/10

 Times Cited Count:5 Percentile:72.09(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Formation and growth of ice XI; A Powder neutron diffraction study

Fukazawa, Hiroshi; Hoshikawa, Akinori; Yamauchi, Hiroki; Yamaguchi, Yasuo*; Ishii, Yoshinobu

Journal of Crystal Growth, 282(1-2), p.251 - 259, 2005/08

 Times Cited Count:18 Percentile:18.11(Crystallography)

We measured neutron diffraction profiles of powdered KOD-doped D2O ice to investigate the formation and growth of ice XI, a deuterium-ordered phase of ice, from ice Ih, a disordered phase. During the measurements, the ice was annealed at 57 K for about 17 h, and then warmed up and kept at 68 K for about 55 h, which are below the transition temperature Tc = 76 K. The diffraction profiles for the doped ice at 57 K did not change with time and were close to those for ice Ih with the deuterium-disordered arrangement. However, when the temperature increased from 57 K to 68 K, the diffraction profiles changed. We carried out the Rietveld analysis with the parameters for a two-phase model to obtain the structural evidence of the appearance and the growth of ice XI. The analysis provided evidence of ice XI as space group Cmc21 at 68 K. The temporal increase of the mass fraction of ice XI showed that nucleation of ice XI began just after warming up to 68 K. Then ice XI grew for several days in the doped ice. The study provides the first structural observation of the growth of ice XI.

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