【公開日：2024.07.25】【最終更新日：2024.04.12】
課題データ / Project Data
課題番号 / Project Issue Number
23NM5334
利用課題名 / Title
KNN-based Pb-free Piezoelectric Materials
利用した実施機関 / Support Institute
物質・材料研究機構 / NIMS
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion（副 / Sub）-
キーワード / Keywords
Piezoelectric materials,電子顕微鏡/ Electronic microscope
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
島村 清史
所属名 / Affiliation
物質・材料研究機構
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）,技術補助/Technical Assistance
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
This work aims at the synthesis of high-performance (K,Na)NbO3 piezoelectric ceramics with good reproducibility and chemical stability. Several powder processing routes were compared in order to elucidate the sensible parameters, followed by spark-plasma sintering at low temperature. Powders were systematically analyzed by scanning electron microscopy (SEM) to assess the evolution of the grains' size and morphology at each processing step. Their composition and homogeneity were confirmed by energy-dispersive spectroscopy (EDS). Additionally, SEM-EDS was also used to observe the microstructure and homogeneity of sintered ceramic samples.
実験 / Experimental
Powder analysis: After synthesizing the KNN phase from commercial raw materials, powders were pulverized into fine particles and post-annealed at temperatures ranging from 700oC to 1000oC in 100oC steps. A fine layer of powder was applied on carbon tape to evaluate their gradual recrystallization as a function of temperature by SEM.
Ceramic analysis: The surface of the sintered ceramic disks was treated by chemical-mechanical polishing so that the grains became visible by SEM. The samples were then fixed onto the sample holders with copper tape. No electrode was sputtered on the surface.
結果と考察 / Results and Discussion
Powder analysis: After pulverization, the obtained fine powders possess randomly shaped grains with the coexistence of submicron- and few-micron-size particles. No significant change was observed after post-annealing at low temperatures. Recrystallization was rather found to start from 900oC, with the partial disappearance of the submicron grains and the rounding of the larger particles, followed by effective grain growth when annealing at higher temperatures. An example of powder recrystallized at 900oC is shown in Figure 1.
Ceramic analysis: The observed ceramics displayed a dense microstructure with micron-sized grains separated by well-defined straight grain boundaries, which indicates grain growth to some extent upon sintering. The ferroelectric domains also appeared as stripes within the grains. The element analysis by EDS revealed a good compositional homogeneity of the samples over the observation area. The variations in grey tones between grains denote their variations in crystallographic orientation. An example of obtained microstructure is shown in Figure 2.
図・表・数式 / Figures, Tables and Equations
Figure 1. SEM image of pulverized KNN powder pulverized and recrystallized at 900oC.
Figure 2. Microstructure of a sintered KNN ceramic prepared from powder recrystallized at 900oC.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
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Lucile Vaschalde, High‐performance KNN piezoceramics with reproducibility and chemical stability. Part I: Solid‐state reaction route, Journal of the American Ceramic Society, 106, 6480-6490(2023).
DOI: https://doi.org/10.1111/jace.19336
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Lucile Vaschalde, High‐performance KNN piezoceramics with reproducibility and chemical stability. Part II: Innovative melt‐reaction route, Journal of the American Ceramic Society, 106, 6491-6499(2023).
DOI: https://doi.org/10.1111/jace.19340
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Lucile Vaschalde, High Piezoelectric Performance in Undoped (K,Na)NbO3 Piezoceramics over a Wide Range of Compositions, Inorganic Chemistry, 62, 18485-18495(2023).
DOI: https://doi.org/10.1021/acs.inorgchem.3c02680
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件