Establishment of structural measurement system for elucidating mechanism of giant piezoelectric response of pseudo-cubic fluctured ferroelectrics

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02641
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: Hiroshima University
• Principal Investigator: Kuroiwa Yoshihiro 広島大学, 先進理工系科学研究科(理), 教授 (40225280)
• Co-Investigator(Kenkyū-buntansha): 大沢 仁志 公益財団法人高輝度光科学研究センター, 分光推進室, 研究員 (00443549) ; 藤井 一郎 山梨大学, 大学院総合研究部, 准教授 (20597645)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 誘電体物性 / ペロブスカイト / X線回折 / 電場印加実験 / 時分割実験 / 結晶構造解析 / 放射光

Outline of Final Research Achievements

We have developed the crystal structure measurement system under applied electric field by means of synchrotron radiation time-resolved single-crystal X-ray diffraction to clarify the mechanism of significant ferroelectricity and piezoelectricity in the lead-free pseudo-cubic perovskite-type oxides, called fluctured ferroelectrics.
The material contains bismuth ions with similar electronic states instead of lead ions. The bismuth ion was found to be off-centered from the high-symmetry position in the crystal and could be ordered in any direction toward the electric filed to form nanodomains when the electric field was applied. We have revealed that the rearrangement of these nanodomains significantly contributes to the dielectric properties.

Free Research Field

構造物性

Academic Significance and Societal Importance of the Research Achievements

誘電体の分野では，近年，環境問題に配意して，チタン酸ジルコン酸鉛等の代替品として，有害な鉛を含まない非鉛圧電材料の開発が盛んである．我々のグループでも非鉛材料の探索を行ってきた結果，ペロブスカイト型構造をもつ擬立方晶0.3BaTiO3-0.1Bi(Mg1/2Ti1/2)O3-0.6BiFeO3（BT-BMT-BF）が優れた強誘電性と圧電特性をもつことを見出した．一般に，立方晶系に帰属する点群の中に極性点群はないことから，立方晶の物質に強誘電性は期待できない．この物質では今までにない新規な仕組みで誘電特性が発現することから，新たな材料設計の指針を示すことができたと考えている．