Layered perovskite engineering: design of ferroelectrics through control of oxygen octahedral rotations

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04496
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic materials/Physical properties
• Research Institution: Kyoto University
• Principal Investigator: Fujita Koji 京都大学, 工学研究科, 教授 (50314240)
• Co-Investigator(Kenkyū-buntansha): 村井 俊介 京都大学, 工学研究科, 助教 (20378805)
• Research Collaborator: Hojo Hajime
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 強誘電体

Outline of Final Research Achievements

Hybrid improper ferroelectricity in layered perovskites, which utilizes nonpolar but ubiquitous rotational/tilting distortions to create polarization, offers an attractive route to the discovery of new ferroelectric and multiferroic materials because its activity derives from geometric rather than electronic origins. In this study, we discover new hybrid improper ferroelectric, Sr3Zr2O7 and (Sr,Ca)3Sn2O7. We also find that the Curie temperature increases linearly up to 800 K with increasing the Ca2+ content in (Sr,Ca)3Sn2O7, i.e., with decreasing the value of tolerance factor. Remarkably, this linear relationship is applicable to the suite of all known A3B2O7 ferroelectrics, indicating that the Curie temperature correlates with the simple crystal-chemistry descriptor based on the ionic-size mismatch.

Free Research Field

工学

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は5%に満たず、応用分野も限定的であった。ハイブリッド間接型強誘電体の物質設計では、元素選択の自由度が直接型の場合と比べて遥かに大きいため、物質探索により高機能な新規強誘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。ハイブリッド間接型強誘電体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。