1990 Fiscal Year Final Research Report Summary
Study of Transformation of Ferroeletric Phase Transition Mechanism by Farーinfrared Fourier Spectroscopy
| Project/Area Number |
01540268
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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 | Shinshu University |
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Principal Investigator |
WADA Mitsuo Faculty of Liberal Arts. Department of Physics, Associate Professor, 教養部, 助教授 (20115653)
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| Co-Investigator(Kenkyū-buntansha) |
MIWA Hirosi Faculty of Liberal Arts, Department of Physics, Professor, 教養部, 教授 (70028108)
SASANE Akinobu Faculty of Science, Department of Chemistry, Associate Professor, 理学部, 助教授 (10020679)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Infrared Fourier Spectroscopy / Far-Infrared / Ferroelectrics / Structural Phase Transition / Transformation of Phase Transition Mechanism / Soft Mode / Raman Scattering |
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| Research Abstract |
The ferroelectrics Li_2Ge_7O_<15> undergoes peculiarly interesting phase transition, where both the dielectric critical slowing-down characteristics of the order-disorder type and the soft phonon mode characteristic in the disp laciveone. In this kind of phase transiton it could be considered the following two cases : (i) The soft phonon becomes overdampened and transforms to the relaxational mode.(ii) There exists a relaxational mode with an independent degree of freedom as well as the soft phonon mode and the character of softening transfers from the phonon to the relaxational mode. This is an important problem to understand the dynamics of structural phase transition.
In the present study we attempt to measure both the soft phonon and the relaxational mode simultaneously by an infrared Fourier spectrometer particularly designed and to observe the transformation of the phase transition mechanism. In the first year a cryostat for optical measurements was purchased by means of the present Grant-in-Aid. The temperature dependence of the far-infrared transmission spectra have been measured with the cryostat and a handーmade furnace. In the paraelectric phase B phonon with the lowest frequency has been confirmed to show softening as the transition temperature was approached from above. This result shows good agreement with that of Raman scattering measurment.
In the second year, to observe both phonon and relaxational mode in the lowerwave number region the improvement of the interferometer has been performed.By means of the interferometer with a high sensitive Si : GA bolometer, the spectra in the frequency region to 4cm^<-1> can be measured. The study is now in progress.
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