Local Ir dedimerization followed by ligand-hole hopping in X-ray irradiated thiospinel

Hiraka, Haruhiro*; Matsumura, Daiju; Horigane, Kazumasa*; Mizuki, Junichiro*

Journal of Physics and Chemistry of Solids, 150, p.109870_1 - 109870_8, 2021/03

https://doi.org/10.1016/j.jpcs.2020.109870

Local structure study of the iron-based systems of BaFeAs 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

https://doi.org/10.1016/j.physc.2018.10.003

-dependence of local distortions in BaFeAs 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 BaFeAs. Arguments on the origins of the 4-fold symmetry breaking in the ground average structure of the tetragonal phase.

Observation of momentum-dependent charge excitations in hole-doped cuprates using resonant inelastic X-ray scattering at the oxygen edge

Ishii, Kenji*; Toyama, Takami*; Asano, Shun*; Sato, Kentaro*; Fujita, Masaki*; Wakimoto, Shuichi; Tsutsui, Kenji*; Sota, Shigetoshi*; Miyawaki, Jun*; Niwa, Hideharu*; et al.

Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09

AA2017-0402.pdf:0.81MB

https://doi.org/10.1103/PhysRevB.96.115148

Study on the deterioration mechanism of layered rock-salt electrodes using epitaxial thin films; Li(Ni, Co, Mn)O and their Zr-O surface modified electrodes

Abe, Machiko*; Iba, Hideki*; Suzuki, Kota*; Minamishima, Hiroaki*; Hirayama, Masaaki*; Tamura, Kazuhisa; Mizuki, Junichiro*; Saito, Tomohiro*; Ikuhara, Yuichi*; Kanno, Ryoji*

Journal of Power Sources, 345, p.108 - 119, 2017/03

https://doi.org/10.1016/j.jpowsour.2017.01.103

The surface structure of the Li(Ni, Co, Mn)O electrode was studied during charge/discharge process using electrochemical methods and X-ray/Neutron scattering techniques. It was found that during charge/discharge process the coverage of spinel structure increased. The spinel structure has low electrochemical activity and is not involved in Li insertion/extraction. After the surface modification, it was found that the coverage of the spinel structure did not increase. Further, it was also found out that the Li concentration at the electrode/electrolyte interface increased.

Negative correlation between electrical response and domain size in a Ti-composition-gradient Pb[(MgNb)Ti]O crystal near the morphotropic phase boundary

Shimizu, Daisuke*; Tsukada, Shinya*; Matsuura, Masato*; Sakamoto, Junya*; Kojima, Seiji*; Namikawa, Kazumichi*; Mizuki, Junichiro; Owada, Kenji

Physical Review B, 92(17), p.174121_1 - 174121_5, 2015/11

https://doi.org/10.1103/PhysRevB.92.174121

The phase diagram and the relationship between the crystal coherence length and electrical response of Pb[(MgNb)Ti]O (PMN-xPT) near the morphotropic phase boundary (MPB) have been precisely investigated using a single crystal with a Ti composition gradient by synchrotron X-ray diffraction and inelastic light scattering at room temperature. The crystal has two boundaries at Ti compositions of 29.0 mol% and 34.7 mol% which correspond to the phase boundaries between the monoclinic B (MB) and C (MC) phases and between the MC and tetragonal (T) phases, respectively. It is shown that there is a strong negative correlation between the electrical response and the crystal coherence length at the sub-m scale. The results are explained by the size effects of domains near the MPB.

Interfacial analysis of surface-coated LiMnO epitaxial thin film electrode for lithium batteries

Suzuki, Kota*; Hirayama, Masaaki*; Kim, K.-S.*; Taminato, So*; Tamura, Kazuhisa; Son, J.-Y.*; Mizuki, Junichiro; Kanno, Ryoji*

Journal of the Electrochemical Society, 162(13), p.A7083 - A7090, 2015/08

https://doi.org/10.1149/2.0111513jes

The effects of surface coatings on LiMnO were investigated using LiMnO epitaxial thin films with a thickness of 30 nm. Bare and surface-coated LiMnO epitaxial thin films were synthesized on SrTiO(111) substrates using a pulsed laser deposition method. The surface coating, which was formed using the solid electrolyte LiPO and had a thickness of 3 nm, improved the reversibility of the electrochemical reactions undergone by the LiMnO epitaxial thin films. The changes induced in the surface structure were maintained during battery operation; in contrast, the bare LiMnO thin film exhibited structural degradation and Mn dissolution. The structural changes induced in the coated electrode and the increase in its surface stability were intrinsic effects of the LiPO coating and improved the electrochemical performance of the LiMnO thin-film electrode.

Mechanistic studies on lithium intercalation in a lithium-rich layered material using LiRuO epitaxial film electrodes and surface X-ray analysis

Taminato, So*; Hirayama, Masaaki*; Suzuki, Kota*; Kim, K.-S.*; Zheng, Y.*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of Materials Chemistry A, 2(34), p.17875 - 17882, 2014/11

https://doi.org/10.1039/C4TA02795G

The surface structure of a lithium-rich layered material and its relation to intercalation properties were investigated by synchrotron X-ray surface structural analyses using LiRuO epitaxial-film model electrodes with different lattice planes of (010) and (001). Electrochemical charge-discharge measurements confirmed reversible lithium intercalation activity through both planes, corresponding to three-dimensional lithium diffusion within the LiRuO. The (001) plane exhibited higher discharge capacities compared to the (010) plane under high rate operation (over 5 C). Direct observations of surface structural changes by surface X-ray diffraction (XRD) and surface X-ray absorption near edge structure (XANES) established that an irreversible phase change occurs at the (010) surface during the first (de)intercalation process, whereas reversible structural changes take place at the (001) surface.

Heterophase fluctuations near in the relaxor ferroelectrics (1-x)Pb(ZnNb)O-xPbTiO ( = 0.09) studied by X-ray diffuse scattering and coherent X-ray scattering

Owada, Kenji; Mizuki, Junichiro*; Matsushita, Mitsuyoshi*; Namikawa, Kazumichi*

Physical Review B, 90(10), p.104109_1 - 104109_12, 2014/09

https://doi.org/10.1103/PhysRevB.90.104109

The paraelectric (PE) to ferroelectric (FE) first-order phase transition of 0.91Pb(ZnNb)O-0.09PbTiO ( = 455 K on cooling) has been studied by the complementary use of X-ray diffuse scattering (XDS) and coherent X-ray scattering (CXS). XDS was mainly used to investigate the FE regions, while CXS was mainly used to investigate the PE regions above on cooling. The diffuse scattering intensity due to the appearance of FE regions shows a maximum at K. The diffuse scattering is dynamic in nature and the softening trend changes to a hardening trend at . This means that the FE instability is maximum at and therefore the FE regions are well stabilized below . The spatial autocorrelation function obtained by CXS, corresponding to the texture of PE regions, starts to rapidly change at about and is most unstable at . We conclude that a heterophase fluctuation occurs between and near the phase transition. The heterophase fluctuation can be expected to correlate to the low-frequency dielectric dispersion and contribute to the phase transition as a precursor phenomenon of the first-order phase transition.

Bipartite magnetic parent phases in the iron oxypnictide superconductor

Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

https://doi.org/10.1038/nphys2906

Instrumental upgrades of the RIXS spectrometer at BL11XU at SPring-8

Ishii, Kenji; Jarrige, I.*; Yoshida, Masahiro*; Ikeuchi, Kazuhiko*; Inami, Toshiya; Murakami, Yoichi*; Mizuki, Junichiro

Journal of Electron Spectroscopy and Related Phenomena, 188, p.127 - 132, 2013/06

https://doi.org/10.1016/j.elspec.2012.12.003