2003 Fiscal Year Final Research Report Summary
Direct grwoth of othorhombic ferroelectric Potassium niobate crystal
| Project/Area Number |
14550010
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Yamaguchi University |
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Principal Investigator |
KOMATSU Ryuichi Yamaguchi University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20314817)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Potassium Niobate / Piezoelectric devices / solution growth / hydrothermal growth / K_2NbO_3F / engineered-domain |
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| Research Abstract |
Potassium niobate (KNbO_3 ; KN) is a ferroelectric material with perovskite structure. Recently this crystal has been given much attention as a piezoelectric substrate with high coupling factors far acoustic device. It is necessary to grow single domain KN crystals of over 2 inches diameter in order to apply them to SAW and BAW devices. This crystal, however, melts incongruently and crystallizes into a cubic perovskite-type structure from its high-temperature solution, which undergoes two phase transformations front cubic to tetragonal at 43 5ーC and from tetragonal to orthorhombic at 225℃. The grown crystal, which belongs to the orthorhombic system includes many complicated domain.
I have been trying direct growth of orthorhombic potassium niobate (KNbO_3) crystal and orthorhombic KN is directly grown from an aqueous solution dissolving K_2NbO_3F as a nutrient. Although the size of each crystal is about 30μ,m or less, all crystals may be single domain. To the best of our knowledge, this is the first report revealing the generation of the singledomain crystal. Grown KNbO_3 crystals have piezoelectricity, Thus it may be concluded that this method is a promising one for the application to SAW and BAW devices. Further investigations to improve this method are necessary before applying it to these devices
Otrhrhombic KN tiny crystal was also grown by the hydrothermal method. KN is grown by spontaneous nucleation in the aqueous solution dissolving KNF. Grown crystal may has engineered-domain structures, and thus it may be useful fro BAW devices instead of Pb bearing piezoelectric devices
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