2002 Fiscal Year Final Research Report Summary
Phase Transition in Hydrogen-Bonded Crystal at Low Temperature under High Pressure
| Project/Area Number |
12440090
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Shizuoka Institute of Science and Technology |
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Principal Investigator |
DEGUCHI Kiyoshi Shizuoka Institute of Science and Technology, Department of Materials Science, Professor, 理工学部, 教授 (10033911)
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| Co-Investigator(Kenkyū-buntansha) |
ENDO Shoichi Osaka University, Research Center for Materials Science at extreme Conditions, Professor, 極限科学センター, 教授 (10001843)
TOKUNAGA Masaharu Hokkaido University, Department of Physics, Professor, 理学研究科, 教授 (60001682)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Ferroelectrics / hydrogen bond / high pressure / KH_2PO_4 / CsH_2PO_4 / PbHPO_4 |
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| Research Abstract |
1. KH_2PO_4 and KD_2PO_4 (1) The crossover of the phase transition mechanism from order-disorder type to displacive type has been found with increasing pressure. (2) The occurrence of the quantum paraelectricty has been observed at low temperature under high pressure
2. L_1TIC_4H_40_6H_2O (1) It was found that the ferroelectric phase transition temperature decreases with increasing the deuteron concentration x, and disappears at x, o.95. (2) This isotope effect in the phase transition temperature is explained on the soft-mode theory
3. C_3H_2PO_4 (1) The pressure-temperature phase diagram was investigated. Two triple points were found; one is the position where the paraelectric phase (phase I), ferroelectric phase (phase II) and pressure-induced antiferroelectric phase (phase III) meet, and the other is the position where the phase I, phaseII, phaseIII and the second pressure-induced antiferroelectric phase (phaseIX) meet. (2) The pressure-temperature phase diagram obtained in the present work is well described by the quasi-one dimensional Ising model
4. PbHPO_4 (1) It was found that the ferroelectric phase transition temperature decreases with increasing pressure, and disappears at 3 Gpa. (2) The pressure-temperature phase diagram of PbHPO_4 is very similar with that KH_2PO_4. Contrary to previous reports, there is no indication for that PbHPO_4 is the qusai-one-dimensional ferroelectric
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