Development of high-performance lead-free piezoelectric single crystals by formation of phase boundary and domain engineering

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K05073
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: University of Yamanashi
• Principal Investigator: FUJII Ichiro 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: 圧電体 / 強誘電体 / 非鉛圧電材料 / 単結晶 / 固相結晶成長法 / ニオブ酸ナトリウムカリウム

Outline of Final Research Achievements

The piezoelectric response of piezoelectric materials can be increased by choosing a composition with a phase transition and aligning a specific crystal axis to an applied electric field /stress direction. In this study, single crystals of modified (K0.5Na0.5)NbO3 (KNN) such as a composition abbreviated as LKNN-BZ-BNT were fabricated by a solid-state crystal growth method. By optimizing fabrication conditions, an LKNN-BZ-BNT single crystal shows a piezoelectric coefficient d33 of 405 pC/N, which is about 1.7 times larger than that of reported polycrystalline ceramics with the same composition and also larger than that of a KNN single fabricated by the same method (d33=153 pC/N).

Free Research Field

無機材料・物性

Academic Significance and Societal Importance of the Research Achievements

Pb(Zr,Ti)O3 (PZT)は圧電素子として電子デバイスに用いられている。しかしながら有毒な鉛を含むため将来RoHS指令等で使用が制限される可能性がある。(K0.5Na0.5)NbO3 (KNN)とその固溶体は代替候補材料の１つである。PZTに比べて圧電特性が小さいので向上させる必要がある。本研究では、KNNより圧電特性が大きく、その温度安定性に優れるKNN固溶体の単結晶を作製し、その圧電特性d33が405 pC/Nと多結晶体の値よりも1.7倍大きいことを明らかにした。KNN系単結晶においても結晶異方性を活かすことで、圧電特性を向上できることを示した。