1988 Fiscal Year Final Research Report Summary
Studies on Growth and Properties of Large Single Crystals of Ferroelectric Polymers
| Project/Area Number |
62460200
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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 |
高分子物性
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| Research Institution | Yamagata University |
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Principal Investigator |
OHIGASHI Hiroji Professor, Department of Engineering, Yamagata University, 工学部, 教授 (90185372)
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| Co-Investigator(Kenkyū-buntansha) |
IKEDA Susumu Professor, Department of Engineering, Yamagata University, 工学部, 助教授 (30007025)
ISHII Fumiaki Assistant Prof., Department of Engineering, Hokkaido University, 工学部, 助手 (30001308)
KOYAMA Kiyohito Associate Prof., Department of Engineering, Yamagata University, 工学部, 助教授 (60007218)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Single Crystal / Polymer Crystallization / High Pressure / Ferroelecticity / PVDF / P(VDF-TrFE) / Ultrasonic Transducer / 超音波顕微鏡 |
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| Research Abstract |
Crystallization and properties of ferroelectric polymers were studied aiming to obtain large single crystals, to elucidate crystallization mechanisms, and to apply them to electronc devices, especially to ultrasonic transducers, using materials of PVDF (poly(vinylidene fluoride)), P(VDF-TrFE)(copolymers of VDF and trifluoroethylene), and P(VDF-TeFE)(copolymers of VDF and tetrafluoroethylene). The followings are the main results of the present studies.
1. Growth of Large Single Crystals: Various methods for crystal growth were applied to P(VDF-TrFE) and P(VDF-TeFE). Among them, we found the crystallization under high pressures and high temperatures is most effective; the resulting single crystals were lamellar crystals about 0.2um thick and 10-100mum wide, and bulk single crystals with 10-20mum in diameter. These single crystals are extended chain crystals grown only in the paraelectric or rotational phase where the molecules undergo rotational vibration with large amplitude. Precise pha
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se diagram as a function of VDF content was obtained for P(VDF-TrFE). 2. Single Crystals of PVDF: Extended-chain beta-form single cystals of PVDF were grown only at high pressure and high temperatures above 2.4kb and 230 C. The single crystals exhibited conspicuous ferroelectricity and strong piezoelectricity which persist up to 205 C. Therefore, high-pressure crystallized PVDF film is usable at highest temperature region among piezoelectric polymers. 3. Studies on Molecular Motion at High Temperatures: The molecular motions correlating to crystallization and Curie transition were studied for P(VDF-TrFE) by means of broad line NMR and dielectric and mechanical measurements. It is found that chain molecules are very mobile along the molecular chains above the curie temperature. 4. Applications to Ultrasonic Transducers: Highly crystallized P(VDF-TrFE) films were applied to various ultrasonic transducers. It is found that these transducers can operate in the wide temperature range (4K-450K) and in the wide frequency range (5-1000MHz). Less
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