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Okajima T.,Kyushu Synchrotron Light Research Center | Okajima T.,Kyushu University | Yasukawa K.,Kyocera Corporation | Umesaki N.,Japan Synchrotron Radiation Research Institute
Journal of Electron Spectroscopy and Related Phenomena | Year: 2010

The local environment of Ca dopants in barium titanate, BaTiO3, is investigated by Ca K-edge X-ray absorption near-edge structure (XANES) spectroscopy. In conjunction with experiments, first-principles calculations by two methods are systematically made. The projector-augmented wave (PAW) method is used to optimize the local structure and obtain the formation energy. The augmented plane wave plus local orbitalsmethodis adopted to obtain theoreticalXANESspectra.Acomparison between experimental and theoretical XANES spectra shows that Ca dopants are located at the Ba2+ sites forming Ca2+. Formation energy calculations of Ca doped BaTiO3 by the PAW method also give the same results. The Ca atom in BaTiO3 is off-centering in comparison with the Ba site in BaTiO3. The off-centering of Ca atom is newly revealed by the combination of XANES spectroscopy and first-principles DFT calculations. © 2010 Elsevier B.V. All rights reserved.

Han D.,Kyoto University | Uda T.,Kyoto University | Nose Y.,Kyoto University | Okajima T.,Kyushu Synchrotron Light Research Center | And 3 more authors.
Advanced Materials | Year: 2012

The existence of tetravalent dysprosium in perovskite-type oxide barium zirconate is confirmed in this work. This discovery will stimulate many researchers in diverse fields such as catalysts, solid state ionics, sensors, and fluorescent materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shigemasa E.,Japan Institute for Molecular Science | Kaneyasu T.,Japan Institute for Molecular Science | Kaneyasu T.,Kyushu Synchrotron Light Research Center | Matsushita T.,Japan Synchrotron Radiation Research Institute | And 3 more authors.
New Journal of Physics | Year: 2010

The autoionization of atomic fragments after core-to-Rydberg excitations in N2 has been studied using high-resolution electron spectroscopy. Doppler profiles are clearly observed on atomic autoionization peaks and show dependence on the symmetries of the excited states. It is demonstrated that information on the femtosecond dissociation dynamics after the Rydberg excitations can be gained through an analysis of the Doppler profiles. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Mizukoshi Y.,Tohoku University | Okajima T.,Kyushu Synchrotron Light Research Center | Masahashi N.,Tohoku University
Applied Catalysis B: Environmental | Year: 2015

Anodization of Ti-6Al-4V alloy in acetic acid aqueous solution resulted in the formation of amorphous oxide on its surface; the amorphous oxide transformed into crystalline oxide primarily consisting of anatase TiO2 by annealing. The annealed anodic oxide, especially those anodized in 1-2molL-1 acetic acid aqueous solution, could photocatalytically decompose acetaldehyde under visible light illumination. X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray absorption near-edge structure spectroscopy analyses showed that the vanadium is pentavalent and exists in an oxygen-tetragonal structure composed of VO43- units. When the vanadate absorbs visible light, the excited electrons move into the conduction band of anatase TiO2 so that recombination with holes was restricted. As a result, the anodic oxide exhibited superior photocatalytic activity under visible light illumination. © 2014 Elsevier B.V.

Magome E.,Kyushu Synchrotron Light Research Center | Moriyoshi C.,Hiroshima University | Kuroiwa Y.,Hiroshima University | Masuno A.,University of Tokyo | Inoue H.,University of Tokyo
Japanese Journal of Applied Physics | Year: 2010

The crystal structure of metastable LuFeO3 synthesized by containerless processing has been revealed to be a non-centrosymmetric structure (space group P63cm) by analyzing the high-energy synchrotron-radiation powder-diffraction data using the maximum entropy method (MEM)/Rietveld method. The structural characteristics are found in the FeO 5 trigonal bipyramid distorted and tilted from the c-axis, which is cause by the hybridization of atomic orbitals between the O atom constituent of the polyhedron and the neighboring Lu atom. The spontaneous polarization expected from the polar structure is estimated at about 5μC/cm2. © 2010 The Japan Society of Applied Physics.

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