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nanocrystalsYoneda, 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：4 Percentile：21.91(Physics, Applied) nanocrystals with cubic shapeYoneda, 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 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.
O thin films on Si (100) by ion beam sputter depositionMao, W.*; Fujita, Masaya*; Chikada, Takumi*; Yamaguchi, Kenji; Suzuki, Akihiro*; Terai, Takayuki*; Matsuzaki, Hiroyuki*
Surface & Coatings Technology, 283, p.241 - 246, 2015/12
Times Cited Count：3 Percentile：13.89(Materials Science, Coatings & Films)Single-phase nanocrystalline thin films of ErO (440) has been first prepared using Si (100) substrates by ion beam sputter deposition at 973 K at a pressure of 
10
Pa and 
-
annealing at 1023 K at a pressure of 
10
Pa. Er silicides formed during the deposition are eliminated via the annealing, which results in the single phase and the smooth surface of the ErO thin films. The epitaxial relationship between Si (100) and ErO (110) is clarified by X-ray diffraction and reflection high energy electron diffraction.
O (001) surface; A DFT studyMao, W.*; Chikada, Takumi*; Shimura, Kenichiro*; Suzuki, Akihiro*; Yamaguchi, Kenji; Terai, Takayuki*
Journal of Nuclear Materials, 443(1-3), p.555 - 561, 2013/11
Times Cited Count：3 Percentile：25.73(Materials Science, Multidisciplinary)In this work, 
calculations based on density functional theory (DFT) and generalized gradient approximation were performed to investigate the structural and electronic properties of the cubic Er
O
(001) surface and H adsorption processes on this surface. Several stable adsorption sites were identified, and at the most energetically favorable adsorption sites it was found that H bonds with O atoms at the cubic ErO (001) surface with an adsorption energy of 295.68 kJ mol
at coverage 1/8 ML, which was inclined to decrease with the increase of H coverage (
1/4 ML). In addition, the calculations revealed that the dissociative H atom configurations have adsorption energies that are at least 152.64 kJ mol greater than the H molecule configurations on the surface. These results are discussed in regard of the hydrogen isotope permeation behavior in the tritium permeation barrier in a fusion reactor.
Mao, W.*; Chikada, Takumi*; Suzuki, Akihiro*; Terai, Takayuki*; Yamaguchi, Kenji
Journal of Plasma and Fusion Research SERIES, Vol.10, p.27 - 32, 2013/02
A tritium permeation barrier (TPB) is strongly required in fusion blankets for the reduction of loss of fuel and radiological hazard. However, the precise tritium permeation mechanism through the TPB coatings has not been clarified yet, because of their complicated crystal structures. To understand the microscopic mechanism, we have not only prepared and characterized nanostructured ceramic ErO thin films, but also studied the energetics and mobility of hydrogen atom in cubic bulk ErO using ab initio density-functional calculations. The estimated diffusion activation energy (
) of interstitial H is somewhat higher than the diffusion energy barrier observed experimentally at 873 K. It is then considered that diffusion and permeation of hydrogen and its isotopes through the ErO coatings are likely to be dominated by the grain boundary rather than by the grain.
Mao, W.*; Chikada, Takumi*; Suzuki, Akihiro*; Terai, Takayuki*; Yamaguchi, Kenji
no journal, ,
O thin films by ion beam sputter deposition methodFujita, Masaya*; Yamaguchi, Kenji; Asaoka, Hidehito; Mao, W.*; Chikada, Takumi*; Suzuki, Akihiro*; Terai, Takayuki*
no journal, ,
no abstracts in English
O film by means of ion beam sputter depositionFujita, Masaya*; Yamaguchi, Kenji; Asaoka, Hidehito; Mao, W.*; Chikada, Takumi*; Suzuki, Akihiro*; Terai, Takayuki*
no journal, ,
no abstracts in English
nanocrystalsYoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Wada, Satoshi*
no journal, ,
High-energy X-ray diffraction measurements were performed to analyze KNbO nanocrystals. We used KNbO nanocrystals with cubic shape. Moreover, these nanocrystals have cubic structure owing to their small crystal size. Therefore, these nanocrystals are ideal for applying the Scherrer's equation. Crystal-growth mechanism was considered with the crystal size obtained by the Scherrer's equation. It was found the growth mechanism of KNbO by comparing the crystal size and average structure obtained by Rietveld analysis and coherent size obtained by atomic pair-distribution function method.
