Development of molecular piezoelectric materials by exploring plastic/ferroelectric ionic crystals

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K19049
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 32:Physical chemistry, functional solid state chemistry, and related fields
• Research Institution: Hokkaido University
• Principal Investigator: HARADA JUN 北海道大学, 理学研究院, 准教授 (00313172)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: 分子性固体

Outline of Final Research Achievements

We developed new plastic/ferroelectric ionic crystals and pressed the powder samples at high temperature to produce bulk polycrystalline samples. The d33 values of the polycrystalline samples were evaluated using a piezoelectric tester, which were found to be very large as molecular crystals (about 80 to 110 pC/N). In these crystals, the large piezoelectricity was observed irrespective of the origin of the ferroelectric polarization, i.e. displacement off cations and anions and dipole moment of polar molecules. The results indicate that the large piezoelectricity found in the plastic/ferroelectric ionic crystal can be attributed to the facile deformation of the crystal lattice under pressure.

Free Research Field

機能物性化学

Academic Significance and Societal Importance of the Research Achievements

無機酸化物セラミクスの強誘電体は圧電材料として産業界で広く用いられている．しかし，高性能材料の多くが有毒な鉛や希少元素を含むため，その代替材料が強く求められている．近年，無毒で豊富な元素からなる分子結晶の強誘電体が大いに注目されているが，圧電材料としての研究展開はほぼ未開拓である．その大きな理由の一つとして，分子結晶は結晶構造の対称性が低く，一般に，多結晶体では圧電体として機能しないことがあげられる．本研究では，我々が最近開発した柔粘性/強誘電性イオン結晶という新しいタイプの強誘電体に着目し，分子結晶として初めて多結晶体での大きな圧電性発現に成功した．