| Co-Investigator(Kenkyū-buntansha) |
IKAWA Hiroyuki Kanagawa Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (30016612)
KAKIHANA Masato Tokyo Institute of Technology, Interdisciplinary Graduate School of Science & Engineering, Associate Professor, 大学院・総合理工学研究科, 助教授 (50233664)
TSURUMI Takaaki Tokyo Institute of Technology, Graduate School of Science & Engineering, Professor, 大学院・理工学研究科, 教授 (70188647)
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| Research Abstract |
In this study, our objective is to clear an origin of a size effect and THz region dielectric response of the ferroelectric microcrystallites. For this objective, the following two points must be required; (I) preparation of ideal defect-free barium titanate microcrystallites with the particle sizes from 10 nm to 1000 nm, and (II) development of powder dielectric measurement method to study dielectric response at MHz region frequency and THz region. As a result, the following four points were found through this study. (1) A 2-step thermal decomposition method of barium titanyl oxalate was developed, and using this method, defect-free and impurity-free barium titanate microcrystallites were successfully prepared with particle sizes from l7 nm to several hundred nm. (2)By the combination between (a) the dielectric measurement using barium titanate suspension with organic solvent and (b) the simulation using a finite element method with submillion order elements, a powder dielectric measu
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rement method was developed, and this method succeeded to estimate the dielectric constants of the powders. (3) By the combination of the above two things, the size dependence on the particle sizes of barium titanate microcrystallites was successfully cleared. Above the prticles with sizes over 200 nm,the dielectric constants were almost constant at around 3000. Below 200 nm, the dielectric constants increased with the decreasing particle size, and at around 70 nm, the dielectric constant became to maximum around 15000. Then, below 70 nm, the dielectric constants decreased drastically with decreasing particle size, and at 17 nm, the dielectric constant became to minimum around 100. (4) Using these barium titanate microcrystallites, the formation of the colloidal crystals was succeeded by the modified colloidal epitaxy method. As the result of the far infra-red measurement using the colloidal crystals of barium titanate microcrystallites, the dielectric response was successfully estimated from a couple THz to a couple hundred THz region. Less
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