1991 Fiscal Year Final Research Report Summary
Study of relaxation process in the incommensurate phase by means of specific-heat spectroscopy.
| Project/Area Number |
02640253
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
EMA Kenji Tokyo Institute of Technology, Department of Physics, Associate Professor, 理学部, 助教授 (80108183)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Specific-heat spectroscopy / Time-dependent heat capacity / Incommensurate phase / Relaxation process / sodium nitrite / Phosphatidylcholine |
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| Research Abstract |
Recently we found that the heat capacity of ferroelectric sodium nitrite shows time-dependence when the temperature is changed suddenly within the incommensurate phase. Such a dynamic behavior of the heat capacity has been reported before for only limited cases including in the vicinity of the glass transition, and this is the first case that the "time-dependent heat capacity" is found in the incommensurate phase.
Before starting the measurement, the precision of the calorimeter was improved. In the new apparatus, the temperature of the thermal bath is measured using an ac-driven wheatstone bridge, which is much more sensitive than the dc-driven bridge. An lock-in amplifier, a digital multimeter, etc, were purchased by the grant.
Using the new apparatus, measurements were done on sodium nitrite by the relaxation method. It was found that the relaxation in the incommensurate phase proceeds over more than a few hundreds seconds, and that the relaxation shows a distinct deviation from the simple exponential behavior. We also done a simultaneous measurement of heat capacity and dielectric constant, and found that their relaxation processes agree quite well with each other.
We also found that similar relaxation processes are seen during the main transition in aqueous suspensions of phosphatidylcholinesky such as DPPC, DMPC, and DSPC. From multi-Frequency ac-mode measurements, the relaxation time and the parameter beta which characterizes the distribution of relaxation time have been estimated. It is to be noted that the rexlaxation time strongly depends on the side-chain length.
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