| Project/Area Number |
02453009
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理化学一般
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
ENOKI Toshiaki Professor, Faculty of Science, Tokyo Institute of Technology, 理学部, 教授 (10113424)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Kazuya Research Associate, Faculty of Science, Tokyo Institute of Technology, 理学部, 助手 (80206466)
MIYAJIMA Seiichi Associate Professor, Institute for Molecular Science, 助教授 (30157648)
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| Project Period (FY) |
1990 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1990: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Keywords | Graphite intercalation compounds / Metallic hydrogen / Hydrogen absorption / Transport phenomena / Electronic structure / ホ-ル効果 / 熱起電力 |
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| Research Abstract |
We investigated electronic properties of hydrogenated-alkali-metal-graphite intercalation compounds, C_<an>NaH, C_<4n>KH_x and C_8RbH_x, by means of electrical conductivities, magnetoresistances, thermoelectric powers, electronic specific heats, ESR, and magnetic susceptibilities. In sodium compounds, thermoelectric powers and c-axis conductivities suggest that the pi-carrier concentration on graphitic planes is considerably small in comparison with that of the isostructural potassium compounds. The absence of intercalate conduction carriers is also demonstrated by these experiments. According to these facts, Na^+-H^--Na^+ sandwiched triple atomic layer intercalates with a stoichiometric composition of Na/H=1, which are inserted between graphitic layers, have a complete ionic lattice with a small concentration of remaining charges, so that the charge transfer rate from the intercalates to graphitic layers is considerably reduced. The magnetoresistances and Hall resistances of the potassium compounds revealed the presence of two kinds of carriers; majority electron carriers on the graphitic pi-band and minority hole carriers on the hydrogen 1s band. The behaviors of the magnetoresistances are analyzed in terms of the two-carrier model. The estimated mobilities of these two kinds of carriers range -10^3cm^2/V.s with different temperature dependence from each other. The large mobilities of the garaphitic pi-carriers are associated with their light mass ranging -0.1m_e. The small electron-phonon coupling -0.4eV for the hydrogen hole carriers on the ionic K^+-H^--K^+sandwiched triple atomic layer lattice causes their large mobilities. The pressure dependence of c-axis resistivities suggests that the c-axis conduction mechanism is governed mainly by the impurity-assisted hopping process, where the overlap of wave functions between the graphitic band and the intercalate band play a dominant role.
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