2007 Fiscal Year Final Research Report Summary
Single Crystal Growth and Domain Control of Potassium Niobate Crystals by Vertical Bridgman method
| Project/Area Number |
18360007
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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 |
Applied materials science/Crystal engineering
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| Research Institution | Shinshu University |
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Principal Investigator |
HOSHIKAWA Keigo Shinshu University, Faculty Educatio, Professor (10231573)
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| Co-Investigator(Kenkyū-buntansha) |
BANBA Noriko Shinshu University, Faculty of Engineering, Associate Professor (90303445)
TAISHI Toshinori Toboku Univereity, Institute of Material Ressarch, Assistant Professor (90397307)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Potassium Niobate / Vertical Bridgman method / Piezoelectricity / Polarization process / Top-seeded solution growth / Platinum crucible |
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| Research Abstract |
Potassium niobate (KNbO_3: KN) is known as a great piezoelectric materials which has large piezoelectric constant and electro-mechanical coupling coefficient. Therefore, KN is expected to be one of the future piezoelectric materials instead of lead-containing piezoelectric ceramics, and it has also been attracting attention as the substrate of filter devices with wide band using surface acoustic wave. However, KN is an incongruent-melting material, therefore, it is widely believed that a KN single crystal can be only grown by solution growth that means the top-seeded solution growth (TSSG) method. In our previous study, we showed that KN single crystals 10 mm in diameter could be grown by vertical Bridgman (VB) method. In this study, growth of KN single crystal 1 inch in diameter was demonstrated by VB method and the electric properties of the grown KN crystal was investigated.
Powdered K_2CO_3 and Nb_2O_5 were mixed in a ratio of K_2CO_3 : Nb_2O_5 = 52.5 : 47.5 mol%, and the mixture was compressed and was calcined. The resulting columned compounds were used as the raw materials. A z-directional KN single crystal was used as the seed, RN crystals 1 inch in diameter were grown by VB method in air. A platinum crucible was used for the growth, and the growth rate was 0.5 mm/h. After the growth, the crystal was cooled slowly near temperatures of its phase transformation. The crystals were cut into wafers and polished, and the wafers were examined by X-ray topography. After the polarization process, the piezoelectricity of the polarized VB-KN samples was evaluated by using impedance analyzer. As the results, cloudy multi-domain KN crystals were grown by VB method. It was confirmed by X-ray topography that the grown crystals were almost single crystal. After the polarization process, the VB-grown KN single crystal revealed piezoelectricity similar as that grown by TSSG method.
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Research Products
(16 results)
