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Journal Articles

Nanoscale structural analysis of Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$

Yoneda, Yasuhiro; Noguchi, Yuji*

Japanese Journal of Applied Physics, 59(SP), p.SPPA01_1 - SPPA01_7, 2020/11

 Times Cited Count:0

We investigate A-site cation ordering in the ferroelectric perovskite Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ (BNT) by synchrotron X-ray total scattering. Although BNT has a problem of a low depolarization temperature, it is promising a lead-free piezoelectric material. Since the depolarization temperature is presumed to correspond to a relaxer like gradual order-disorder phase transition, local structure analysis is necessary to understand the structure of the diorder phase. Through this approach, the elusive connection between chemical heterogeneity and structural heterogeneity is revealed. Because of the large randomness, the Ti off-center shift is averaged out beyond the unit cell and the structure becomes very close to the average structure beyond the unit cell.

Journal Articles

Shell evolution of $$N$$ = 40 isotones towards $$^{60}$$Ca; First spectroscopy of $$^{62}$$Ti

Cort$'e$s, M. L.*; Rodriguez, W.*; Doornenbal, P.*; Obertelli, A.*; Holt, J. D.*; Lenzi, S. M.*; Men$'e$ndez, J.*; Nowacki, F.*; Ogata, Kazuyuki*; Poves, A.*; et al.

Physics Letters B, 800, p.135071_1 - 135071_7, 2020/01

 Times Cited Count:1 Percentile:22.94(Astronomy & Astrophysics)

Excited states in the $$N$$ = 40 isotone $$^{62}$$Ti were populated via the $$^{63}$$V($$p$$,$$2p$$)$$^{62}$$Ti reaction at $$sim$$200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using $$gamma$$-ray spectroscopy. The energies of the $$2_1^+ rightarrow 0_{rm gs}^+$$ and $$4_1^+ rightarrow 2_1^+$$ transitions, observed here for the first time, indicate a deformed Ti ground state. These energies are increased compared to the neighboring $$^{64}$$Cr and $$^{66}$$Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings.

Journal Articles

Synchrotron radiation-based techniques available at JAEA advanced characterization nanotechnology platform (Japan Atomic Energy Agency)

Yoneda, Yasuhiro; Yoshigoe, Akitaka; Takeda, Yukiharu; Shiwaku, Hideaki; Matsumura, Daiju; Shobu, Takahisa; Tamura, Kazuhisa

Materia, 58(12), p.763 - 769, 2019/12

This is an introduction to the equipment provided for each implementation period belonging to the structure analysis platform in the nanotechnology platform.

Journal Articles

Short- and middle-ranges order structures of KNbO$$_3$$ nanocrystals

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Nagata, Hajime*; Ohara, Koji*; Wada, Satoshi*

Japanese Journal of Applied Physics, 58(SL), p.SLLA03_1 - SLLA03_7, 2019/11

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

Journal Articles

Synthesis of new perovskite-type oxyfluorides, BaInO$$_{2}$$F and comparison of the structure among perovskite-type oxyfluorides

Katsumata, Tetsuhiro*; Suzuki, Ryo*; Sato, Naoto*; Suzuki, Shumpei*; Nakashima, Mamoru*; Inaguma, Yoshiyuki*; Mori, Daisuke*; Aimi, Akihisa*; Yoneda, Yasuhiro

Journal of Solid State Chemistry, 279, p.120919_1 - 120919_8, 2019/11

 Times Cited Count:1 Percentile:66.91(Chemistry, Inorganic & Nuclear)

Journal Articles

Quasifree neutron knockout from $$^{54}$$Ca corroborates arising $$N=34$$ neutron magic number

Chen, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Chazono, Yoshiki*; Navr$'a$til, P.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Raimondi, F.*; et al.

Physical Review Letters, 123(14), p.142501_1 - 142501_7, 2019/10

 Times Cited Count:5 Percentile:14.38(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Relation between the structure and tolerance factor for perovskite-type oxyfluorides

Katsumata, Tetsuhiro*; Inaguma, Nobuyuki*; Mori, Daisuke*; Aimi, Akihisa*; Yoneda, Yasuhiro

Seramikkusu, 54(9), p.629 - 632, 2019/09

Crystal structure analysis of ABO$$_3$$ perovskite-type oxyfluoride were performed by using high-energy synchrotron X-ray measurement. The effect of tolerance factor appeared in the local structure. The average structure of perovskite-type oxyfluoride found to be a cubic structure in the traditional crystal structure analysis.

Journal Articles

Local structure analysis of PbTiO$$_3$$ in high-temperature cubic phase

Yoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*

Ferroelectrics, 538(1), p.57 - 62, 2019/05

 Times Cited Count:1 Percentile:100(Materials Science, Multidisciplinary)

High-energy X-ray diffraction study was performed on lead titanate (PbTiO$$_3$$). 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.

Journal Articles

Observation of simulated fuel debris using synchrotron radiation

Yoneda, Yasuhiro; Harada, Makoto; Takano, Masahide

Transactions of the Materials Research Society of Japan, 44(2), p.61 - 64, 2019/04

We performed three-dimensional observation of simulated fuel debris using Synchrotron Computed Tomography (CT). CT was used to make the inside of fuel debris clear. The CT observation provides that a clear contrast in the zirconia rich part and concrete rich part. Zirconia heavier than concrete moved to the lower part when crystals precipitate and aggregates near the bottom surface. As a result, phase separation occurs. The phase separation is caused by the difference in the composition ratio of zirconia, and can also be observed difference in crystal growth mode by composition ratio.

Journal Articles

Local structure study of the iron-based systems of BaFe$$_2$$As$$_2$$ and LiFeAs by X-ray PDF and XAFS analyses

Li, S.*; Toyoda, Masayuki*; Kobayashi, Yoshiaki*; Ito, Masayuki*; Ikeuchi, Kazuhiko*; Yoneda, Yasuhiro; Otani, Akira*; Matsumura, Daiju; Asano, Shun*; Mizuki, Junichiro*; et al.

Physica C, 555, p.45 - 53, 2018/12

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

${it T}$-dependence of local distortions in BaFe$$_2$$As$$_2$$ and LiFeAs by X-ray PDF and XAFS methods. Although PDF data exhibit anomaly at the structure transition temperature, EXAFS data exhibit no anomaly. Data supporting the local orthorhombicity at 300 K in the tetragonal phase for BaFe$$_2$$As$$_2$$. Arguments on the origins of the 4-fold symmetry breaking in the ground average structure of the tetragonal phase.

Journal Articles

Local structure and phase transitions of KNbO$$_3$$

Yoneda, Yasuhiro; Ohara, Koji*; Nagata, Hajime*

Japanese Journal of Applied Physics, 57(11S), p.11UB07_1 - 11UB07_6, 2018/11

 Times Cited Count:4 Percentile:50.71(Physics, Applied)

Local structure analysis of KNbO$$_3$$, 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.

Journal Articles

Local structure analysis of KNbO$$_3$$ nanocrystals with cubic shape

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Ohara, Koji*; Wada, Satoshi*

Transactions of the Materials Research Society of Japan, 43(2), p.93 - 96, 2018/04

KNbO$$_3$$ nanocrystals were grown by solvothermal technique assisted by a microwave treatment. We performed high-energy X-ray diffraction to extract average and local structural parameters. The particle size can be evaluated by the Scherrer's equation. The unit cell size was reduced as the particle size increased. The local structure was found to be a rhombohedral structure, which was similar to that of the bulk KNbO$$_3$$.

Journal Articles

Raman scattering study of the ferroelectric phase transition in BaTi$$_2$$O$$_5$$

Tsukada, Shinya*; Fujii, Yasuhiro*; Yoneda, Yasuhiro; Moriwake, Hiroki*; Konishi, Ayako*; Akishige, Yukikuni*

Physical Review B, 97(2), p.024116_1 - 024116_7, 2018/02

 Times Cited Count:9 Percentile:27.96(Materials Science, Multidisciplinary)

Uniaxial ferroelectric BaTi$$_2$$O$$_5$$ with a Curie temperature $$T_{rm C}$$ of 743 K was investigated to clarify its paraelectric-ferroelectric phase transition behavior. The mechanism is discussed on the basis of the structure from short to long ranges determined by synchrotron X-ray diffraction and the lattice dynamics probed by Raman spectroscopy. Using a combination of experimental results and first-principles calculations, we explain the phase transition. Ti vibration of TiO$$_6$$ octahedral units is frozen in the ferroelectric phase and the space group changes from nonpolar $$C2/m$$ to polar $$C2$$.

Journal Articles

Local structure analysis of (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ synthesized by malic acid complex solution method

Yoneda, Yasuhiro; Takada, Eri*; Nagai, Haruka*; Kikuchi, Takeyuki*; Morishita, Masao*; Kobune, Masafumi*

Japanese Journal of Applied Physics, 56(10S), p.10PB07_1 - 10PB07_7, 2017/10

 Times Cited Count:2 Percentile:79.95(Physics, Applied)

A monoclinic phase was discovered in (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ solid solution ceramics grown by a malic acid complex solution method. The average and local structures of this monoclinic phase were analyzed by synchrotron X-ray measurements. The local structure can be reproduced by assuming a rhombohedral model, that is the same local structure of KNbO$$_3$$. The results demonstrate that the monoclinic average structure is observed as a disordered rhombohedral structure.

Journal Articles

Local structure analysis of relaxor Pb(Mg$$_{1/3}$$Nb$$_{2/3}$$)O$$_3$$

Yoneda, Yasuhiro; Taniguchi, Hiroki*; Fu, D.*

Ferroelectrics, 513(1), p.1 - 6, 2017/09

 Times Cited Count:4 Percentile:69.03(Materials Science, Multidisciplinary)

An EXAFS study of lead magnesium niobate was performed at the Nb K edge and at the Pb L3 edge at 300 K. Two Nb-O bond lengths of 1.91 and 2.10${AA}$ are observed and there is no significant modification of the local environment of the Nb atoms compared with NaNbO$$_3$$ and AgNbO$$_3$$. The weak Pb L3 EXAFS signal indicated a strong static disorder, which can be extracted by PDF analysis.

Journal Articles

In-beam $$gamma$$-ray spectroscopy of $$^{35}$$Mg via knockout reactions at intermediate energies

Momiyama, Satoru*; Doornenbal, P.*; Scheit, H.*; Takeuchi, Satoshi*; Niikura, Megumi*; Aoi, Nori*; Li, K.*; Matsushita, Masafumi*; Steppenbeck, D.*; Wang, H.*; et al.

Physical Review C, 96(3), p.034328_1 - 034328_8, 2017/09

 Times Cited Count:2 Percentile:67.12(Physics, Nuclear)

no abstracts in English

Journal Articles

Low-$$Z$$ shore of the "island of inversion" and the reduced neutron magicity toward $$^{28}$$O

Doornenbal, P.*; Scheit, H.*; Takeuchi, Satoshi*; Utsuno, Yutaka; Aoi, Nori*; Li, K.*; Matsushita, Masafumi*; Steppenbeck, D.*; Wang, H.*; Baba, Hidetada*; et al.

Physical Review C, 95(4), p.041301_1 - 041301_5, 2017/04


 Times Cited Count:15 Percentile:10.04(Physics, Nuclear)

no abstracts in English

Journal Articles

Local structure analysis of ZrN, and Dy$$_{0.5}$$Zy$$_{0.5}$$N surrogate materials for fast reactor nitride fuel

Yoneda, Yasuhiro; Tsuji, Takuya; Matsumura, Daiju; Okamoto, Yoshihiro; Takaki, Seiya; Takano, Masahide

Transactions of the Materials Research Society of Japan, 42(2), p.23 - 26, 2017/04

ZnN is a possible candidate for the diluent material for nitride fuels containing transuranium elements. Pellets of inert matrix material ZrN, and surrogate nitride fuel material Dy$$_{0.5}$$Zr$$_{0.5}$$N, are fabricated for the purpose of investigating the crystal structure. Lattice parameters of Dy$$_{1-x}$$Zr$$_x$$N followed the Vegard's low, in spite of the large lattice mismatch ($$sim$$ 7%) between DyN and ZrN. Local structure analysis was performed by X-ray absorption fine structure (XAFS) and atomic pair-distribution function (PDF) methods. The Zr-N nearest neighbor bond distance changed as changing the Dy composition. The complex local structure of DyN and ZrN is related to the preferable effects of ZrN.

Journal Articles

Local structure analysis of NaNbO$$_3$$ and AgNbO$$_{3}$$ modified by Li substitution

Yoneda, Yasuhiro; Aoyagi, Rintaro*; Fu, D.*

Japanese Journal of Applied Physics, 55(10S), p.10TC04_1 - 10TC04_5, 2016/10

 Times Cited Count:5 Percentile:61.22(Physics, Applied)

We analyzed the local structures of NaNbO$$_3$$ and Na$$_{0.94}$$Li$$_{0.06}$$NbO$$_3$$ by combining the X-ray absorption fine structure (XAFS) and atomic pair-distribution function (PDF) techniques. NaNbO$$_3$$ 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$$_3$$ 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$$_3$$.

Journal Articles

Local structure analysis of ferroelectric materials by collaborating XAFS and PDF

Yoneda, Yasuhiro

Seramikkusu, 51(10), p.689 - 693, 2016/10

We report the results of synchrotron X-ray studies of BaTiO$$_3$$ and NaNbO$$_3$$. These materials occur ferroelectric phase transitions in which the average structure changes from a tetragonal to rhombohedral structure. However, the refinements of local structures indicates that the structures in ferroelectric phases have the rhombohedral symmetry. The middle-range order structure of BaTiO$$_3$$ and collaboration between PDF and XAFS in NaNbO$$_3$$ are also discussed.

188 (Records 1-20 displayed on this page)