Development of molecular ferroelectric crystals using plastic ionic crystals: flexible control over crystal orientations and polarization directions

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04126
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Functional solid state chemistry
• Research Institution: Hokkaido University
• Principal Investigator: Harada Jun 北海道大学, 理学研究院, 准教授 (00313172)
• Research Collaborator: INABE tamotsu ; TAKAHASHI yukihiro
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 分子性固体

Outline of Final Research Achievements

Molecular ferroelectric crystals have recently attracted growing interest as potential alternatives to lead-based ceramic ferroelectrics. In this study, we developed a new type of molecular ferroelectric crystals, i.e., plastic/ferroelectric ionic crystals, which have a plastic crystal phase at high temperature and ferroelectric phases at lower temperatures. Because of the cubic crystal symmetry in the high-temperature plastic crystal phase, the crystals exhibited multiaxial ferroelectricity, which is unique relative to conventional molecular crystals. The plastic/ferroelectric ionic crystals showed ferroelectric polarization switching in the form of polycrystalline pellets. Free-standing polycrystalline films can be easily prepared by pressing powdered samples owing to the malleability of the plastic crystals. The obtained films exhibited relatively large piezoelectric responses.

Free Research Field

機能物性化学

Academic Significance and Societal Importance of the Research Achievements

現在広く用いられている高性能な強誘電体の多くは有毒な鉛を含むため，その代替材料の開発が強く求められている．本研究で開発した柔粘性/強誘電性イオン結晶は，分子性結晶の特長である溶媒に可溶で高い加工性をもち，無機酸化物の特長である高対称で自在な分極方向変調性を示すだけでなく，金属材料の特長である塑性加工性をも兼ね備えた非常にユニークな機能材料である．この材料の開発を進めることで，現在広く使用されている含鉛セラミクス強誘電体材料の代替となるだけでなく，これまでの材料にはない新しい用途が生み出されることが期待される．