| Project/Area Number |
13450118
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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 | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Tohoku University |
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Principal Investigator |
NAKAMURA Kiyoshi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (00005365)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAZAKI Daisuke Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (20333867)
YAMADA Ken Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (80134021)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2002: ¥5,500,000 (Direct Cost: ¥5,500,000)
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| Keywords | potassium niobate / piezoelectricity / pseudo-cubic crystal / Ferroelectrics / electromechanical coupling factor / domain / thickness-extensional vibration / KNbO_3 |
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| Research Abstract |
The purpose of this research is to elucidate the engineered domain structures of pseudo-cubic ferroelectric crystal KNbO_3 and the high piezoelectricity, and to develop domain control methods and piezoelectric devices utilizing the high coupling factor. The results obtained in this project are summarized as follows: 1. The orientation dependence of various electromechanical coupling factors for KNbO_3 crystal have been calculated and the cut with the highest coupling factor among all known piezoelectrics for the thickness-extensional mode has been found. 2. It was shown that the strain vs. electric-field curve for the pseudo-cubic (001)_<pc> cut of KNbO_3 had a linear characteristic for a low field, but it was hysteretic due to occurrence of 60゜ domains for a high field and exhibited a much higher strain than that estimated theoretically. 3. Chemical etching of crystals for removing micro-cracks lead to no occurrence of 60゜ domain, resulting in non-hysteretic behaviors even for a high electric field. 4. Domain structural change was examined when subjected to heating and cooling through the phase transition temperature and was explained qualitatively. The method for keeping the single domain state when heating through the phase transition temperature was devised and demonstrated to work out. 5. Engineered domain structures were formed by applying an electric field along the (001)_<pc> axis while heating and cooling through the phase transition point. The piezoelectric behavior was demonstrated to exhibit little hysteresis. The domain structure was shown for the first time to consist of two kind of 90゜ laminar domains. 6. It was demonstrated that the KNbO_3 ultrasonic transducer has a more efficient and broader-band characteristic as compared with those of PZT ceramics and LiNbO_3 crystals. To realize higher frequency ultrasonic transducers an ECR-PLD system for epitaxial growth of high quality KNbO_3 films was developed.
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