2012 Fiscal Year Final Research Report
Elucidation of grain-alignment mechanism of ceramics polycrystals by reactive diffusion technique
| Project/Area Number |
23656399
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Multi-year Fund |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
FUKUDA Koichiro 名古屋工業大学, 工学(系)研究科(研究院), 教授 (90189944)
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| Co-Investigator(Renkei-kenkyūsha) |
ASAKA Toru 名古屋工業大学, 工学(系)研究科(研究院), 助教 (80525973)
YOSHIDA Hideto 東京大学, 理学(系)研究科(研究院), 技術職員 (30376553)
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| Project Period (FY) |
2011 – 2012
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| Keywords | 結晶配向 / 組織制御 / 反応拡散 / イオン伝導体 / アパタイト |
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| Research Abstract |
We have prepared the highly c-axis-oriented polycrystalline material of apatite-type La9.50Si6026.25 by isothermal heating of the sandwich-type La2SiO5/La2Si2O7/La2SiO5 diffusion couple at 1873 K for 50 h. The resulting polycrystal was characterized using optical microscopy, X-ray diffractometry and impedance spectroscopy. The annealed couple was mechanically processed, and the thin-plate electrolyte consisting of the textured polycrystal was obtained. The oxide-ion conductivity along the c-axis steadily increased from 2.0 X 10-2 S/cm to 7.9 X 10-2 S/cm with increasing temperature from 723 to 1073 K. The conductivity of this material was, at 723 - 973 K, ca. 2.5 times higher than that of the c-axis-oriented apatite polycrystal of La9.33Si6O26. These two materials have the identical activation energy of conduction (0.35 eV), and hence the conduction mechanism must be the same. Both crystal structures of La9.50Si6O26.25 and La9.33Si6O26 at ambient temperature (space group P63/m) showed the appreciable positional disordering of 0 atoms (12i site) that are bonded to Si atoms, together with the anharmonic displacements of La atoms (4f and 6h sites). The former structure is further characterized by the positional disordering of channel oxide ions (2a and 4e sites) as well as the presence of interstitial oxide ions (6h site), which would contribute to the higher conductivity along the c-axis.
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[Journal Article] Oxide-Ion Conductivity of Highly c-Axis-Oriented Apatite-Type Lanthanum Silicate Polycrystal Formed by Reactive Diffusion between La2SiO5 and La2Si2O72011
Author(s)
K. Fukuda, T. Asaka, R. Hamaguchi, T. Suzuki, H. Oka, A. Berghout, E. Bechade, O. Masson, I. Julien, E. Champion, and P. Thomas
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Journal Title
Chem. Mater.
Volume: Vol.23
Pages: 5474-5483
DOI
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