| Project/Area Number |
11555166
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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 | 展開研究 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | TOKYO INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
ITOH Mituru Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (30151541)
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| Co-Investigator(Kenkyū-buntansha) |
SAKABE Yukio Murata Cooperation, Department Manager, 技術開発本部, 部長(研究職)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥13,800,000 (Direct Cost: ¥13,800,000)
Fiscal Year 2000: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1999: ¥9,000,000 (Direct Cost: ¥9,000,000)
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| Keywords | Ferroelectric / Field-Induced Effect / Quantum Paraelectrics / Perovskite / Isotope Effect / 電界効果 / ラマンスペクトル / 量子強誘電性 / ドメイン壁状態 / 電場効果 |
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| Research Abstract |
Field Dependence of Quantum Ferroelectric
Typical quantum paraelectric, (Ln, Na)TiO_3 discovered by our group, was fabricated into epitaxial thin film. This is the first example of the fabrication of single crystal(Ln, Na)TiO_3 Dielectric susceptibility of this thin film was measured and found that maximum dielectric constant for this material is 180 and becomes a constant below 60 K.Bias dependence was measured for this material and no dependence on bias was found against 10kV/m. This was attributed to the random-field stabilization of the paraelectric state. Contrary to this result, quantum paraelectric SrTiO_3 shows very large bias dependence. Hydrostatic pressure depressed the fluctuating quantum paraelectricity into stable quantum paraelectricity. This depression was interpreted as due to the volume effect of the quantum fluctuation.
Ferroelectricity and Ferroelectric Relaxor Induced by Random Field
Evolution of the relaxor-like ferroelectricity has been considered to originate from
… More
a mismatch between average valance and local valance of conetituent ions. However, the relaxor-like ferroelectricity only by the strong size fluctuation among A-site ions. When Sr ion in SrTiO_3 is replaced by Ca and Ba to keep the lattice constant through the whole composition, the solid solution charges from quantum paraelectric to ferroelectric and finally to relaxor. This is the first example of the evolution of ferroelectricity without heterovalent-ion substitution.
Field Dependence of Quantum Ferroelectricity
Recent our researches on quantum ferroelectrics have elucidated that classical long range ferroelectric domain can not develop under quantum fluctuation. The coexistence of quantum fluctuation and polar fluctuation leads to a formation of nanosize domains. This nano domains response to the external ac field by relation of the orientation, also by the increase in the volume between each domain. This is called "domain-wall state" and is considered to cause a large non-linearity against large electric field.
Perspective
The results obtained in this study show a promising concept of the "Field-sensitive ferroelectrics", which is applicable to the design of tunable ferroelectric. Less
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