Control of Phase Transition Temperature on Environmental Friendly Lead-free Piezoelectric Ceramics based on Bismuth Sodium Titanate

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04564
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Tokyo University of Science
• Principal Investigator: Nagata Hajime 東京理科大学, 理工学部電気電子情報工学科, 教授 (70339117)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 非鉛圧電セラミックス / チタン酸ビスマスナトリウム / 脱分極温度 / 急冷処理

Outline of Final Research Achievements

Bismuth sodium titanate [(Bi1/2Na1/2)TiO3, BNT]-based ceramics is attracting attention as a candidate material for environment-friendly lead-free piezoelectric materials because it exhibits relatively good piezoelectric properties. However, the depolarization temperature Td at which the piezoelectricity disappears is as low as about 100 to 200oC. This is one of the major concerns for the practical piezoelectric applications of BNT-based ceramics. We have experimentally found that Td could be increased about 50 to 80oC by quenching treatment from 1000oC after sintering without deteriorating the excellent piezoelectricity. In addition, it was clarified that the mechanism is strongly related to the increase in rhombohedral distortion of crystal structure and the increase in the domain size.

Free Research Field

電子機能性材料

Academic Significance and Societal Importance of the Research Achievements

本研究成果で提案するクエンチ処理は、BNT系セラミックスのTd高温化に寄与するだけでなく、ハイパワー圧電特性（超音波性能）を維持する結果を示した。すなわち、本成果はBNT系セラミックスを環境にやさしい非鉛圧電材料として、超音波応用デバイスへの実用化していく点において、大きく前進させたものと考えられる。また、構造歪みの増大やドメインサイズの増大はビスマス系ペロブスカイト型強誘電体セラミックスの相転移制御において新たな学術的コンセプトを与えたものと考えられる。