2003 Fiscal Year Final Research Report Summary
Preparation of Preferentially Oriented Titanium Oxide Thin Films by Topotactic Structural Transformation Reaction
| Project/Area Number |
13650894
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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 |
無機工業化学
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| Research Institution | Kagawa University |
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Principal Investigator |
FACULTY Feng Kagawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (80274356)
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| Project Period (FY) |
2001 – 2003
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| Keywords | Topotatic structural transformation / Soft chemical method / Oriented thin film / Barium titanate / Titanium oxide / Layered titanate / Exfoliation of layered compound / metal substrate |
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| Research Abstract |
In the preparations of preferentially oriented thin films, usually epitaxial crystal growth techniques are utilized. In this case, a single crystal substrate and lattice matching between the substrate crystal and the film crystal are necessary, meaning the high cost for the preparation of the epitaxial films. In the present study, we developed a novel process for the preparation of an oriented layered titanate thin film on stainless steel and Ti metal substrates by using an exfoliation-restacking technique, and preparation of oriented BaTiO_3 and TiO_2 thin films from the layered titanate film by using topotactic structural transformation reactions.
In this process, a layered H^+-form titanate H_<1.07>Ti_<1.73>O_4・nH_2O (HTO) was used as precursor. HTO powder sample was exfoliated into the nano-sheets of elementary layer of its structure by reacting with an n-propylamine solution. The HTO thin film was prepared by dipping the substrates into the HTO nano-sheet solution and then drying in air at room temperature. The HTO nano-sheets restack on the surface of the substrate and form a preferentially oriented film of the layered titanate after drying. Oriented thin films of anatase and rutile types of TiO_2 were obtained after heat-treatment at 600 and 800℃ respectively. A BaTiO_3 film with a preferred orientation along [110] direction was obtained by hydrothermal treatment of the HTO film in a Ba(OH)_2 solution. The cubic BaTiO_3 film was obtained under low temperature conditions and tetragonal BaTiO_3 film under high temperature conditions. A capacitance measurement indicated that the BaTiO_3 film prepared by present method showed a much higher dielectric constant than that of BaTiO_3 films prepared by other methods. The method developed in this study will not be limited in the preparations of the titanium oxide films, but also useful for the preparation of other metal oxides oriented films.
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