Science and function exploration of improper ferroelectrics
| Project/Area Number |
19H02433
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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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| Review Section |
Basic Section 26020:Inorganic materials and properties-related
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| Research Institution | Kyoto University |
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Principal Investigator |
FUJITA Koji 京都大学, 工学研究科, 教授 (50314240)
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| Co-Investigator(Kenkyū-buntansha) |
村井 俊介 京都大学, 工学研究科, 助教 (20378805)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2021)
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| Budget Amount *help |
¥17,030,000 (Direct Cost: ¥13,100,000、Indirect Cost: ¥3,930,000)
Fiscal Year 2021: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
Fiscal Year 2020: ¥10,270,000 (Direct Cost: ¥7,900,000、Indirect Cost: ¥2,370,000)
Fiscal Year 2019: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
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| Keywords | 強誘電体 / 圧電体 |
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| Outline of Research at the Start |
膨大なペロブスカイト化合物の中で，反転中心のない構造をもつ物質（強誘電体や圧電体）は5%に満たず，応用分野も限定的であった．これは，金属元素－酸素間の共有結合形成に基づく同じ設計指針で物質開拓が行われてきたためである．この状況を一変させたのが，層状ペロブスカイトを対象とした新しい機構の登場である．研究代表者は，ペロブスカイト関連酸化物において「酸素八面体の回転」によって結晶構造の反転対称性が破れることを初めて実証した．さらにこの原理を拡張して，従来の直接型強誘電体とは異なる物質群，すなわち「間接型」強誘電体を発見した．本研究では，酸素八面体回転に基づく間接型強誘電体の基礎学理を構築する．
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| Outline of Final Research Achievements |
Piezoelectricity and improper ferroelectricity in layered perovskites, which utilize ubiquitous rotation/tilting distortions to break inversion symmetry, offer an attractive route to the discovery of new functional materials because their activity derives from geometric rather than electronic origins. In this study, we demonstrate that a layered perovskite oxide, SrLa2Sc2O7, crystallizes in a polar orthorhombic symmetry (space group A21am) at room temperature. The switchable polarization indicative of ferroelectricity can be revealed in a plot of polarization versus electric field.
In addition, we show that layered perovskite oxides, AgRTiO4 (R: rare earth), adopt an acentric tetragonal structure at room temperature. Interestingly, these compounds exhibit biaxial negative thermal expansion. We ascribe the observed phenomenon to the interplay between the structural distortions that alter the octahedral connectivity and shape.
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| Academic Significance and Societal Importance of the Research Achievements |
膨大なペロブスカイト化合物の中で強誘電体・圧電体は5%に満たず、応用分野も限定的であった。酸素八面体回転に基づく強誘電体・圧電体の物質設計では、元素選択の自由度が大きいため、この方向での物質探索により高機能な新規強誘電体・圧電体が登場する可能性は大いにある。また、現在は鉛を含むペロブスカイト強誘電体Pb(Zr,Ti)O3が圧電素子として広範に利用されているが、環境保全の観点からこれを代替する無鉛圧電材料の開発が強く求められている。新しい機構に基づく新材料の開発はそのような産業界の要望にも応えることができる。
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Report
(4 results)
Research Products
(32 results)
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[Journal Article] Dehydration of Electrochemically Protonated Oxide: SrCoO2 with Square Spin Tubes2021
Author(s)
Li Hao-Bo、Kobayashi Shunsuke、Zhong Chengchao、Namba Morito、Cao Yu、Kato Daichi、Kotani Yoshinori、Lin Qianmei、Wu Maokun、Wang Wei-Hua、Kobayashi Masaki、Fujita Koji、Tassel Cedric、Terashima Takahito、Kuwabara Akihide、Kobayashi Yoji、Takatsu Hiroshi、Kageyama Hiroshi
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Journal Title
Journal of the American Chemical Society
Volume: 143
Issue: 42
Pages: 17517-17525
DOI
Related Report
Peer Reviewed / Int'l Joint Research
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[Presentation] Development of Hybrid Improper Ferroelectric Layered Perovskites2019
Author(s)
Suguru Yoshida, Hirofumi Akamatsu, Ryosuke Tsuji, Olivier Hernandez, Haricharan Padmanabhan, Alexandra S. Gibbs, Ko Mibu, Shunsuke Murai, Venkatraman Gopalan, Katsuhisa Tanaka, and Koji Fujita
Organizer
The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13)
Related Report
Int'l Joint Research
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