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Nb
)O
Yoneda, Yasuhiro; Taniguchi, Hiroki*; Noguchi, Yuji*
Journal of Physics; Condensed Matter, 33(3), p.035401_1 - 035401_8, 2021/01
Times Cited Count：4 Percentile：33.7(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：27.39(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.
Nb)OYoneda, Yasuhiro; Taniguchi, Hiroki*; Fu, D.*
Ferroelectrics, 513(1), p.1 - 6, 2017/09
Times Cited Count：7 Percentile：35.49(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
are observed and there is no significant modification of the local environment of the Nb atoms compared with NaNbO and AgNbO. The weak Pb L3 EXAFS signal indicated a strong static disorder, which can be extracted by PDF analysis.
revealed by the neutron diffraction studyKori, Shunsuke*; Igarashi, Taichi*; Okazaki, Ryuji*; Taniguchi, Hiroki*; Tanisaki, Ichiro*; Yasui, Yukio*; Igawa, Naoki; Hoshikawa, Akinori*; Ishigaki, Toru*
no journal, ,
The neutron powder diffraction for the multiferroic material, NdCrTiO has been carried out to investigate the development of the magnetic order in the material. We found the intensities of magnetic peaks increased with decreasing temperature below the transition temperature T
. We discuss temperate dependence of magnetic moments and the development of magnetic order.
Nb)OYoneda, Yasuhiro; Taniguchi, Hiroki*
no journal, ,
Pb(MgNb)O (PMN) is one of the so-called relaxer ferroelectrics. It is the feature that electrical susceptibility shows anomaly in a wide temperature range and a wide frequency range. It is thought that the behavior of PMN represents the origin of a relaxer above the phase transition temperature (225K) and the relaxer behaves as a usual ferroelectrics below the phase transition temperature. We analyzed PMN by using synchrotron radiation measurements. From the local structure analysis using XAFS, PMN has large randomness at the position of Pb, implying the origin in the relaxer characteristic. PDF analysis revealed that the change of local structure corresponded to the Burns temperature, that is the anomaly temperature of the electrical susceptibility.
Ishikawa, Hiroki*; Tada, Eiji*; Nishikata, Atsushi*; Taniguchi, Naoki; Tachikawa, Hirokazu*
no journal, ,
In current concept of geological disposal of high-level radioactive waste, the vittrified wastes are stored in metallic container which is called overpack, and then disposed in deep underground. Similarly in direct disposal of spent nuclear fuel, the fuel assemblies are disposed in deep underground contained in metallic disposal container. In order to ensure the long term integrity and safety of overpack or disposal container, corrosion monitoring was performed using electrochemical impedance spectroscopy (EIS) technique.
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 490
C, 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.
Takeuchi, Yukio*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Yoshita, Hirofumi*; Fujita, Kazuki*; Takahashi, Yusuke*; Kuramoto, Takayuki*; Nomura, Naoki*; Hagiwara, Hiroki; Dohi, Terumi; et al.
no journal, ,
no abstracts in English
Nb)OYoneda, Yasuhiro; Taniguchi, Hiroki*; Noguchi, Yuji*
no journal, ,
Many structural models have been proposed for relaxer ferroelectrics Pb(MgNb
O. We have shown that the Pb-O distance obtained from the mean structure differs from the Pb-O distance obtained from the X-ray absorption fine structure (XAFS). Since the deviation between the average structure and the local structure is considered to be derived from the characteristic environment of the Pb atom, the behavior similar to that of the Pb atom in the pyrochlore type Pb
SnO
is assumed and the local structure is assumed. I tried structural modeling. A pair-distribution function (PDF) analysis was performed, and as a result of local structure modeling, it was suggested that there is a network structure of Pb atoms that is different from the periodicity of the lattice system.
