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Yoneda, Yasuhiro
JSAP Review (Internet), 2023, p.230202_1 - 230202_7, 2023/00
It is important to determine whether a sample is a single phase or not in order to improve the quality of ferroelectrics. Therefore, we have succeeded in developing a detection method for trace amounts of segregated phases by using two-body correlation distribution function (PDF) in addition to X-ray diffraction, which has been conventionally used to detect impurities. In the X-ray diffraction pattern of the BaTiO
-BiFeO solid solution, it appears as a single phase with a rhombohedral structure. However, when the PDF was calculated from the obtained diffraction pattern, it was found that not only the component derived from the rhombohedral crystal structure calculated from the average structure but also the BaTiO component was mixed and segregated. By using PDF in this way, it has become possible to detect fine segregation phases on the order of nanoscale.
Yoneda, Yasuhiro
Oyo Butsuri, 91(12), p.729 - 735, 2022/12
It is important to determine whether a sample is a single phase or not in order to improve the quality of ferroelectrics. Therefore, we have succeeded in developing a detection method for trace amounts of segregated phases by using two-body correlation distribution function (PDF) in addition to X-ray diffraction, which has been conventionally used to detect impurities. In the X-ray diffraction pattern of the BaTiO-BiFeO solid solution, it appears as a single phase with a rhombohedral structure. However, when the PDF was calculated from the obtained diffraction pattern, it was found that not only the component derived from the rhombohedral crystal structure calculated from the average structure but also the BaTiO component was mixed and segregated. By using PDF in this way, it has become possible to detect fine segregation phases on the order of nanoscale.
-BaTiO solid solutionsYoneda, Yasuhiro; Kim, S.*; Mori, Shigeo*; Wada, Satoshi*
Japanese Journal of Applied Physics, 61(SN), p.SN1022_1 - SN1022_10, 2022/11
Times Cited Count：1 Percentile：15.88(Physics, Applied)Local structural analysis of the (1-
) BiFeO-BaTiO solid solution was performed by PDF analysis of the data obtained in the synchrotron radiation high-energy X-ray diffraction experiment. First, when XAFS experiments were performed and sample screening was performed, it was found that structural fluctuations were large in the BiFeO-rich composition. Therefore, PDF analysis of a sample with BiFeO-rich composition was performed. As a result, it was found that although the average structure is a cubic structure, the local structure can be reproduced with a rhombohedral crystal structure, and there is a displacement that breaks the symmetry of the rhombohedral structure in a composition with a large fluctuation.
NaTiO in high-temperature phasesYoneda, Yasuhiro; Noguchi, Yuji*
Japanese Journal of Applied Physics, 60(SF), p.SFFA08_1 - SFFA08_10, 2021/11
Times Cited Count：4 Percentile：35.58(Physics, Applied)BiNaTiO (abbreviated as BNT) is a lead-free material but exhibits relatively large piezoelectric properties, a lot of researches have been conducted. We performed local structural analysis using high-quality BNT with a stoichiometrically correct composition, and found a chemical order structure of Bi/Na in locally. BNT undergoes a phase transition to a cubic phase at 400
C. We estimated that a new disorder structure will appear in the high-temperature phase. In the high temperature phase, pair distribution function (PDF) analysis using synchrotron radiation high-energy X-rays was performed. As a result, we found that Bi shifts from 200C, and this shift becomes an order parameter for the phase transition.
Nb
)OYoneda, Yasuhiro; Taniguchi, Hiroki*; Noguchi, Yuji*
Journal of Physics; Condensed Matter, 33(3), p.035401_1 - 035401_8, 2021/01
Times Cited Count：4 Percentile：32.53(Physics, Condensed Matter)Nanoscale structural analysis of relaxor Pb(MgNb)O (PMN) was performed using synchrotron high-energy X-ray diffraction measurements. Although PMN is a well-known relaxor ferroelectric material, the average structure is a cubic structure, and various models have been proposed to explain the ferroelectric microstructure. We performed a wide-range local structure analysis up to 20 nm using the pair distribution function (PDF). As a result, it was found that the structure of PMN changed depending on the distance and it was a glass-like structure.
in high-temperature cubic phaseYoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*
Ferroelectrics, 538(1), p.57 - 62, 2019/05
Times Cited Count：5 Percentile：26.93(Materials Science, Multidisciplinary)High-energy X-ray diffraction study was performed on lead titanate (PbTiO). Short-range order structure was revealed using atomic pair-distribution function (PDF) method. In the high-temperature cubic phase, there is a large deviation between local and average structure. Especially, Pb atoms deviated from the cubic lattice framework, but establish Pb-O-Pb random network.
Yoneda, Yasuhiro; Ohara, Koji*; Nagata, Hajime*
Japanese Journal of Applied Physics, 57(11S), p.11UB07_1 - 11UB07_6, 2018/11
Times Cited Count：18 Percentile：59.12(Physics, Applied)Local structure analysis of KNbO, which is the parent compound for lead-free piezoelectric materials, have been performed by X-ray pair-distribution functions (PDF). The refinements of local structure in wide temperature ranges indicates that only the rhombohedral structure can describe the observed bond distributions within the unit cell. The rhombohedral distortion maintained locally in all four phases.
and AgNbO
modified by Li substitutionYoneda, Yasuhiro; Aoyagi, Rintaro*; Fu, D.*
Japanese Journal of Applied Physics, 55(10S), p.10TC04_1 - 10TC04_5, 2016/10
Times Cited Count：6 Percentile：29.03(Physics, Applied)We analyzed the local structures of NaNbO and Na
Li
NbO by combining the X-ray absorption fine structure (XAFS) and atomic pair-distribution function (PDF) techniques. NaNbO is known to be an antiferroelectric material at room temperature. It also undergoes a diffuse phase transition, in which an orthorhombic and a rhombohedral phases coexist over a wide temperature range. We identified a rhombohedral ground state structure of NaNbO and assumed an order-disorder-type phase. We also found a disorder feature in the nearest-neighbor bond distance corresponding to the Nb-O bonds. The disordered bond distribution disappeared when Na was substituted for Li. A similar disorder feature was found in AgNbO.
Okamoto, Yoshihiro; Akabori, Mitsuo; Ito, Akinori; Ogawa, Toru
Journal of Nuclear Science and Technology, 39(Suppl.3), p.638 - 641, 2002/11
We report local structural features of molten UCl with LiCl-KCl eutectic probed by the U L-edge XAFS(X-ray absorption fine structure). The XAFS measurements were performed in a transmission mode at the BL27B station of the Photon Factory(High Energy Accelerator Organization, Tsukuba, JAPAN). Sample prepared by chlorination of uranium hydride and then reduction with zinc powder was sealed in a quartz cell under reduced pressure. The nearest U
-Cl
distance and the coordination number of Cl around U ion were obtained by a curve fitting of the 1st shell XAFS function k
(k). The pair potential in the U-Cl correlation was evaluated from XAFS simulation by combinational use of the MD and the FEFF8. In addition, valence state of uranium in the melt was evaluated by XANES(X-ray absorption near edge structure) spectra.
Okamoto, Yoshihiro; Fukushima, Kazuko*; Iwadate, Yasuhiko*
Journal of Non-Crystalline Solids, 312(314), p.450 - 453, 2002/10
Local structure of molten ZnBr
was investigated by both of the Zn and the Br XAFS (X-ray absorption fine structure) measurements above their K-absorption edge at 723 K. The nearest Zn
-Br distance was determined to be 2.46 
for the Zn XAFS and 2.45 for the Br XAFS. The coordination number of Br ion around Zn was about 4. On the other hand, that of Zn ion around Br was about 2. The 1st Br-Br distance was estimated to be 3.9 . They shows that a tetrahedral coordinate (ZnBr
)
exists and most of the coordinate connects with the next ones through Br ion. The two XAFS functions in the molten ZnBr were reproduced by the combination of the molecular dynamics(MD) simulation and the FEFF7 computations.
Okamoto, Yoshihiro; Akabori, Mitsuo; Motohashi, Haruhiko*; Ito, Akinori; Ogawa, Toru
Nuclear Instruments and Methods in Physics Research A, 487(3), p.605 - 611, 2002/07
Times Cited Count：27 Percentile：83.19(Instruments & Instrumentation)Measurement system for the high temperature XAFS was developed for investigating the local structure of hygroscopic molten salts like rare earth halides. Solid sample was enclosed in the upper tank of the quartz cell having a sandglass shape under reduced pressure to avoid oxygen and moisture. The measurement was carried out at the electric furnace of the highest arrival temperature 1273K. After melting, the sample runs down through the melt path with 0.1mm(or 0.2mm) thickness to the lower tank. The minimum energy which could be measured was about 10keV mainly due to the absorption of the quartz. It was confirmed that the measurement of the expensive hygroscopic sample became possible in the present work.
Ishida, Hisashi
Proceedings of the International Conference on Bioinformatics 2002 (CD-ROM), 6 Pages, 2002/02
no abstracts in English
Shimoyama, Iwao
Hoshako, 15(1), p.12 - 19, 2002/01
Since the prediction of the possibility that carbon nitride would have super hard property which exceeds that of diamond, considerable efforts to synthesize this material have been employed. However, local structures in carbon nitride films synthesized have not been revealed enough. We study the local structures utilizing synchrotron radiation and revealed the existence of three kinds of local structures in carbon nitride films, i.e., cyanic structure which has C≡N triple bond, pyridine-like structure which has C=N double bond, and graphite-like structure in which carbon atom is substituted by nitrogen atom in graphite network. In this article, I explain the method of near edge X-ray absorption fine structure (NEXAFS) that we used for this study, and from the comparison with X-ray photoelectron spectroscopy (XPS), I comment the availability of NEXAFS to study the local structures in new materials.
Eu-M
ssbauer spectroscopic study of the fluorite-type oxide solid solutions, Eu
M
O
(M=Zr,Ce)(0
y1.0)Masaki, Nobuyuki; Guillermo, N. R. D.; Otobe, Haruyoshi; Nakamura, Akio; Izumiyama, Yuki*; Hinatsu, Yukio*
Advances in Science and Technology, 29, p.1233 - 1240, 2000/00
no abstracts in English
Katayama, Yoshinori; *; *; *; *; *; Tsuji, Kazuhiko*
Review of High Pressure Science and Technology, 7, p.251 - 253, 1998/00
no abstracts in English
Mizuki, Junichiro
Nihon Kessho Gakkai-Shi, 39(1), p.31 - 36, 1997/00
no abstracts in English
Yoneda, Yasuhiro
no journal, ,
A 
-type diffractometer, which is dedicated to Japan Atomic Energy Agency, is equipped on a bending magnet beamline at SPring-8. We performed atomic pair-distribution function (PDF) analysis on crystalline materials. For example, local and middle-ranges order analysis of surrogate materials of Dy
Zr
N for nitride fuel was performed by using this apparatus.
Yoneda, Yasuhiro
no journal, ,
An invitation lecture about atomic pair distribution function (PDF) method which is one of the local structural analysis method using synchrotron radiation X-rays was performed. Since the PDF analysis can be clarified the nano-scale order structure, as well as the short-range order structure, the PDF analysis is structural analysis method indispensable to ferroelectric materials with a manifested organization of physical properties through the domain. I showed that the results of the PDF analysis for relaxor ferroelectrics. The PDF is able to visualize the structure of the lead atoms, which deviates from the average structure.
in high-temperature cubic phaseYoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*
no journal, ,
Lead titanate, PbTiO, has a tetragonal structure having a large c/a ratio at room temperature. A phase transition to the paraelectric phase at 490C, structural changes to cubic. However, just above the transition point to the paraelectric phase, the phonon modes of the still ferroelectric is observed. Therefore, spontaneous polarization using a sample of reversible high quality, perform high-energy X-ray diffraction experiments were subjected to structural analysis in a wide temperature range from room temperature to 800C. Short range order structure analysis and atomic two pairs distribution function (atomic pair-distribution function, PDF) was performed using. A comparison local structures at room temperature of the observed local structure and relaxor Pb (MgNb)O (PMN) with 800C of PbTiO, network structure similar to the relaxor PMN is present in the high temperature phase of PbTiO It is considered to have.
Shamoto, Shinichi
no journal, ,
The current nanoscience challenges standard crystallographic analysis based on a space group, which fails to observe the specific disorders in the crystal structures. Various states have been discovered between liquid and solid phases like a liquid crystal even in an inorganic solid. This aspect can be extended to various electronic and magnetic states.
