1995 Fiscal Year Final Research Report Summary
Study on the soft mode around the phase transition tenperature of ferroelectric crystals through low-frequency dielectric spectrum measurements.
| Project/Area Number |
06640458
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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 Science and Engineering, Professor, 理工学部, 教授 (10033911)
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| Project Period (FY) |
1994 – 1995
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| Keywords | ferroelectrics / phase tansition / soft mode / critical relaxational mode |
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| Research Abstract |
The measurement system of low-frequency dielectric spectrum has been developed. This measurement system is able to speedly provide reliable measurement data in the frequency region of 45 MHz to 15 GHz, and in the temperature region of 80 K to 450 K.
The dielectric spectra of ferroelectric crystals, LHP,LHA,TSCC and D-LTT have been investigated by using the developed measurement system. The results are summarized as follows ;
1.Apparent dielectric critical slowing-down are found around the phase transition temperatures of LHP and LHA.The results indicate that the mechanism of the ferroelectric phase transition is of an order-disorder.
2.TSCC is known to be the first example which shows both the critical softening of phonon mode and the critical slowing-down of the ralaxational mode. The present study clarifies that the critical relaxational mode reported previously is not the relaxational mode but the over-damped soft mode.
3.Critical relaxational mode is not observed in deuterated LTT (D-LTT), as in not-deuteraterd LTT.The nature of the phase transition is not affected by deuteration. However, It is found that the displacive ferroelectric LTT shows unusual deuteration effect of phase transition ; the transition temperature is lowered with increasing the ratio of deuteron. The ferroelectric phase transition disappears in the crystal with the deuteration ratio more than 95%.
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