| Project/Area Number |
22K04686
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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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 |
YI Wei 京都大学, 工学研究科, 准教授 (50903431)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
Fiscal Year 2024: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2023: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2022: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
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| Keywords | Polar metal / Ferroelectric / Layered Perovskites |
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| Outline of Research at the Start |
The research will be carried out on layered perovskite oxides as following: (1) chemical doping by inequivalent cation substitution on B-site. (2) O-vacancy introduced by high pressure synthesis method. (3) determine ferroelectricity and metallicity phase diagram for doping system.
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| Outline of Annual Research Achievements |
Ferroelectric metals combining ferroelectricity and metallicity, two seemingly mutually exclusive properties in one system, strongly stirred the research community. Ferroelectrics with a spontaneous and reversible electric polarization, are promising for a wide range of applications and pose a number of fundamental questions. In general, they are insulators. Introducing itinerant charge carriers is expected to screen the long-range coulomb forces and quench ferroelectricity. This conventional concept was broken when the existence of ferroelectric-like metal was theoretically proposed by Anderson and Blount and the ferroelectric-like structural transition in metallic was experimentally observed in LiOsO3. Although several theoretical predictions of ferroelectric/polar metals have been reported, the experimental observations are still rather rare so far. The core issue of this project is to extend the members of this material family and research the unconventional properties of ferroelectric/polar metal materials.
We have achieved two things in the fiscal year (FY) 2023. First, the conducting properties of a new metallic transition metal oxide (same as LiOsO3) with a ferroelectric-like structural transition at low temperature was successfully investigated. Second, A-site cation disorder inducing ferroelectricity in layered perovskite oxides La2SrSc2O7 with Ruddlesden-Popper type structure was demonstrated and published as an article in the Journal of the American Chemistry Society.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
As of the end of FY 2023, we achieved 80% of the final goal of this research project.
A non-centrosymmetry structure phase transition of one new transition metal oxide, which has the LiNbO3-type structure at room temperature, has been suggested by synchrotron x-ray diffraction and neutron diffraction at variable temperature 5-300K. The metallic conductivity was also measured at variable temperature. The loss of inversion symmetry is confirmed by the observations via convergent-beam electron diffraction (CBED) at low temperature.
Rational design of ferroelectric in Ruddlesden-popper layered perovskite La2SrSc2O7 has been achieved. The ferroelectric A21am structure at room temperature and the second phase transition to paraelectric Amam structure at 600 K are determined by experimental observations. Combining the experimental results with first-principles calculations, we verify the role of Sr2+/La3+ distributions is key to controlling the ferroelectricity.
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| Strategy for Future Research Activity |
For the future study in FY2024, we will continue the project and conduct detailed evaluations of physical properties and structures, such as the observations of convergent-beam electron diffraction (CBED) performed to confirm the loss of inversion symmetry. The preparations and structure analyses of ferroelectric/polar metal compounds will be continually done in layered perovskites with disordered Sr/La cations on A-site. We also aim to modulate the functionality of ferroelectric/polar metal materials by the doping carriers.
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