2007 Fiscal Year Final Research Report Summary
Study on disordered structure and ionic diffusion in amorphous solids with non linear ultrasonic resonance
| Project/Area Number |
18540321
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics I
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| Research Institution | The University of Tokushima |
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Principal Investigator |
NAKAMURA Koichi The University of Tokushima, Institute Technology and Science, Department of Quantum materials Science, lecturer (20284317)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHITAKA Michihiro The University of Tokushima, Institute Technology and Science, Department of Quantum materials Science, Assistant Prof. (00174061)
MORIGA Toshihiro The University of Tokushima, Institute Technology and Science, Department of Materials Science and Engineering, Assistant Prof. (90239640)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Lithium ion secondary battery / Piezoelectric material / Mechanical milling / NMR / Electrical conductivity / LiCoO_2 / LiNbO_2 |
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| Research Abstract |
lithium cobalt oxide has been used as a cathode material of lithium ionic rechargeable battery so far and advanced cathode material with higher charge/discharge properties has been expected. In this study, our aim is to obtain new insights into structural change and ionic diffusion in amorphous like lithium compounds by using fly-AIRS-Al milling (MM) method to control disorder of crystal structure. Electrical resistivity of milled lithium cobalt oxide is analyzed by a Delve model on the basis of a single ion hopping process The results indicate that in lithium cobalt oxide prepared by MM the moderate MM condition with short milling time stimulates the lithium ionic diffusion through the defects, while the excessive MM condition with long milling time degrades the lithium ionic diffusion becalm a large number of defects induced by excessive MM effectively cut off diffusion path fir migrating lithium ions In lithium cobalt oxide, it hind that the NMR line width of ^7Li NMR spectrum becom
… More
es broader with increasing milling time. The MM process changes magnetic state of cobalt which is primitively a low spin configuration in the CoO_6 octahedron so that the line broadening is ascribed to the magnetic width due to tee magnetic moment of cobalt induced by MM.
On the other hand, piezoelectric material LiNbO_3 and LiTaO_3 milled fir several hours show the motional narrowing of ^7Li-NMR line width at mom temperature. This means that disordered crystal structure induces a fast ionic diffusion in these materials. From the NMR spectrum analysis by decomposing spectrum, it hind that several percent of lithium in the materials would diffuse with much lower activation energy of 0.3 eV than primitive activation energy of 1.6 eV in non-milled LiNbO_3 from the analysis by decomposing NMR spectrum, consisting of a narrow and broad spectrum.
Echo decay time, T_2 of propagating wave in a SiO_2 particle was measured over the temperature range from room temperature to 500 K by two-pulse phonon echo technique. The values of T_2 are temperature independent so that SiO_2 might be a standard material to detect energy loss out of particles contacting other fine powder samples. Phonon echo of SiO_2 particles is strongly affected by mixing fine particles. Only 0.5 mol% of LiNbO_3 fine powder suppresses phonon echo intensity at room temperature in the air, because the wet fine powder prevent from vibration of SiO_2 particles. Phonon echo intensity increases due to dehydrating fine powder at 393K because it makes vibration of SiO_2 particles better. However, a large amount of mixed fine powder has suppressed phonon echo intensity even at high temperatures so that disappearance of phonon echo does not depend only on humidity. A further study will plan to study an origin of disappearance of phonon echo in mixed particle system. Less
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[Journal Article] NMR Study on Defect Structure in β-LiGa2008
Author(s)
Daisuke, Nishioka, Koichi, Nakamura, Yoshitaka, Michihiro, Takashi, Ohno, Kazuo, Kuriyama, Hiromi, Hamanaka, Masahito, Yahagi
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Journal Title
Journal of the Physical Society of Japan 77
Pages: 034604-1-7
Description
「研究成果報告書概要(欧文)」より
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