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Ishida T.,Nagoya University | Kawasaki T.,EcoTopia Science Institute | Kawasaki T.,Japan Fine Ceramics Center | Kawasaki T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | And 3 more authors.
Microscopy | Year: 2015

A phase reconstruction method based on multiple scanning transmission electron microscope (STEM) images was evaluated quantitatively using image simulations. The simulation results indicated that the phase shift caused by a single atom was proportional to the 0.6th power of the atomic number Z. For a thin SrTiO3 [001] crystal, the reconstructed phase at each atomic column increased according to the specimen thickness. The STEM phase images can quantify the oxygen vacancy concentration if the thickness is less than several nanometers. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved.


Ishida T.,Nagoya University | Ishida T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Kawasaki T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Kawasaki T.,EcoTopia Science Institute | And 7 more authors.
Microscopy | Year: 2015

A novel technique for reconstructing the phase shifts of electron waves was applied to Cs-corrected scanning transmission electron microscopy (STEM). To realize this method, a new STEM system equipped with an annular aperture, annularly arrayed detectors and an arrayed image processor has been developed and evaluated in experiments. We show a reconstructed phase image of graphite particles and demonstrate that this new method works effectively for high-resolution phase imaging. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved.


Nishio K.,Global Research Center for Environment and Energy based on Nanomaterials Science | Ohnishi T.,Global Research Center for Environment and Energy based on Nanomaterials Science | Ohnishi T.,Japan International Center for Materials Nanoarchitectonics | Ohnishi T.,Japan National Institute of Materials Science | And 7 more authors.
Journal of Power Sources | Year: 2016

LiCoO2 is epitaxially grown on SrTiO3 (100) substrates with (104) orientation. Because the LiCoO2 film is grown with its c-axis parallel to four equivalent 〈111〉 axes of the SrTiO3, the (104)-oriented film exhibits four-domain structure on the SrTiO3 (100) substrate. Introducing off-cut angle to the substrate surface breaks the equivalency between the four 〈111〉 axes of the SrTiO3 substrate to induce preferential growth of specific orientation with the c-axis in a descending direction of off-cut surface. Increasing off-cut angle and lowering deposition rate promote the preferential growth, because they facilitate step-flow growth mode, and finally align the c-axes in the domains completely into one 〈111〉 direction of the SrTiO3 substrate. The LiCoO2 film delivers a discharge capacity of 90 mAh g−1 at a low discharge rate of 0.01 C, and 25% of capacity is kept even at a high rate of discharge with 100 C. © 2016 Elsevier B.V.


Xing J.,CAS Shanghai Institute of Ceramics | Xing J.,Japan National Institute of Materials Science | Takeguchi M.,Japan National Institute of Materials Science | Hashimoto A.,Japan National Institute of Materials Science | And 3 more authors.
Applied Physics Letters | Year: 2014

Photovoltaic behavior of a CaFe2O4/ZnFe 2O4 p-n multi-junction was investigated with electron holography combined with an in situ light irradiation system. Potential profiles of the samples with and without light irradiation were extracted to measure the open circuit photovoltage generated either by the whole heterojunction superstructure or from each p-n junction. Investigation on the variation in the energy band configuration under light irradiation revealed the mechanism involved in the photoelectric effect, with respect to the properties of the heterojunction and its periodic quantum structure. © 2014 AIP Publishing LLC.


Chauhan S.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Mori T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Mori T.,Hokkaido University | Masuda T.,Station X | And 10 more authors.
ACS Applied Materials and Interfaces | Year: 2016

Pt-CeOx nanowire (NW)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on Pt were prepared by a combined process involving precipitation and coimpregnation. A low, 5 wt % Pt-loaded CeOx NW/C electrocatalyst, pretreated by an optimized electrochemical conditioning process, exhibited high ORR activity over a commercially available 20 wt % Pt/C electrocatalyst although the ORR activity observed for a 5 wt % Pt-loaded CeOx nanoparticle (NP)/C was similar to that of 20 wt % Pt/C. To investigate the role of a CeOx NW promotor on the enhancement of ORR activity on Pt, the Pt-CeOx NW interface was characterized by using hard X-ray photoelectron spectroscopy (HXPS), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Microanalytical data obtained by these methods were discussed in relation to atomistic simulation performed on the interface structures. The combined techniques of HXPS, TEM-EELS, and atomistic simulation indicate that the Pt-CeOx NW interface in the electrocatalyst contains two different defect clusters: Frenkel defect clusters (i.e., 2Pti •• - 4Oi″ - 4Vo •• - VCe″″) formed in the surface around the Pt-CeOx NW interface and Schottky defect clusters (i.e., (PtCe″ - 2VO •• - 2CeCe′) and (PtCe″ - VO ••)) which appear in the bulk of the Pt-CeOx NW interface similarly to Pt-CeOx NP/C. It is concluded that the formation of both Frenkel defect clusters and Schottky defect clusters at the Pt-CeOx NW heterointerface contributes to the promotion of ORR activity and permits the use of lower Pt-loadings in these electrocatalysts. © 2016 American Chemical Society.


Li W.,Nagoya University | Li W.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Tanji T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Tanji T.,EcoTopia Science Institute
Microscopy | Year: 2014

Off-axis electron holography can be used to measure the inner potential of a specimen from its reconstructed phase image and is thus a powerful technique for materials scientists. However, abrupt reversals of contrast from white to black may sometimes occur in a digitally reconstructed phase image, which results in inaccurate information. Such phase distortion is mainly due to the digital reconstruction process and weak electron wave amplitude in some areas of the specimen. Therefore, digital image processing can be applied to the reconstruction and restoration of phase images. In this paper, fringe reconnection processing is applied to phase image restoration of a crystal structure image. The disconnection and wrong connection of interference fringes in the hologram that directly cause a 2π phase jump imperfection are correctly reconnected. Experimental results show that the phase distortion is significantly reduced after the processing. The quality of the reconstructed phase imagewas improved by the removal of imperfections in the final phase. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy.


Bui K.M.,University of Tsukuba | Bui K.M.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Dinh V.A.,Osaka University | Okada S.,University of Tsukuba | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2016

Based on density functional theory, we have systematically studied the crystal and electronic structures, and the diffusion mechanism of the NASICON-type solid electrolyte Na3Zr2Si2PO12. Four possible elementary processes are addressed: three inner-chain and one inter-chain processes. In inner-chain processes, Na tends to move inside the Na diffusion chain, while Na moves across the Na diffusion chain in the inter-chain process. The activation energies for the inner-chain and inter-chain processes are 230 meV and 260 meV, respectively. By combining possible elementary processes, three preferable pathways along a, b, and c directions are found. © the Owner Societies 2016.


Bui K.M.,Global Research Center for Environment and Energy based on Nanomaterials Science | Bui K.M.,University of Tsukuba | Dinh V.A.,Osaka University | Okada S.,University of Tsukuba | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2015

The crystal and electronic structures, electrochemical properties and diffusion mechanism of NASICON-type Na3V2(PO4)3 have been investigated based on the hybrid density functional Heyd-Scuseria-Ernzerhof (HSE06). A polaron-Na vacancy complex model for revealing the diffusion mechanism is proposed for the first time in the field of Na-ion batteries. The bound polaron is found to favorably form at the first nearest V site to the Na vacancy. Consequently, the movement of the Na vacancy will be accompanied by the polaron. Three preferable diffusion pathways are revealed; these are two intra-layer diffusion pathways and one inter-layer pathway. The activation barriers for the intra-layer and inter-layer pathways are 353 meV and 513 meV, respectively. For further comparison, the generalized gradient approximation with an onsite Coulomb Hubbard U (GGA+U) is also employed. © the Owner Societies.


Li W.,Nagoya University | Li W.,EcoTopia Science Institute | Zhang J.,EcoTopia Science Institute | Zhang J.,Global Research Center for Environment and Energy Based on Nanomaterials Science | And 2 more authors.
Journal of Electron Microscopy | Year: 2013

In electron holography, an abrupt reversal of contrast from white to black may occur in a digitally reconstructed phase image, potentially resulting in inaccurate phase information. There are two types of such abrupt reversals. One is a phase jump of 2π during the digital reconstruction process; in this case, the phase can be unwrapped and smoothly connected for such a jump. The other is caused by the disconnection of interference fringes due to weak electron-wave amplitude in some areas of the specimen. We propose a searching technique for finding the disconnection points based on mathematical morphology and then correcting the interference fringes. Finally, a comparatively accurate phase information image is reconstructed from the corrected interference fringes. © 2013 The Author.

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