【公開日：2023.07.31】【最終更新日：2024.05.23】

課題データ / Project Data

課題番号 / Project Issue Number

22UT0058

利用課題名 / Title

異種元素偏析アルミナ粒界の原子構造解析とその物性研究

利用した実施機関 / Support Institute

東京大学 / Tokyo Univ.

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）その他/Others（副 / Sub）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions

キーワード / Keywords

電子顕微鏡/Electron microscopy,表面・界面・粒界制御/ Surface/interface/grain boundary control

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)

楊 楚楚

所属名 / Affiliation

東京大学

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）-

利用した主な設備 / Equipment Used in This Project

UT-004：環境対応型超高分解能走査透過型電子顕微鏡

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

Grain boundaries (GBs) are two-dimensional defects in the crystal, with different atomic structures from those in the perfect crystal. During annealing, dopants or impurities prefer to segregate in the GBs, which can strongly affect the properties of polycrystalline ceramics. With the-state-of-the-art scanning transmission electron microscopy (STEM), it is possible to investigate how these additive atoms segregate in the GBs. However, the effect of the annealing atmosphere on GB segregation behaviors is still unclear at atomic scale and remains to be studied. In this study, we have prepared a Ti-diffused Σ7 GB Al₂O₃ in the reducing atmosphere and then annealed in air to reveal the effect of different annealing environment on the segregation behaviors.

実験 / Experimental

An Al₂O₃ bicrystal with Σ7 GB was fabricated by bonding two single crystals (>99.99%) at 1500°C for 10 h in air. To prepare the sample with a Ti-diffused GB, we deposited the Ti film on the (0001) surface of the bicrystal by a vacuum evaporator. The sample was then annealed at 1400°C for 10 h in an Al₂O₃ furnace tube (99.6% pure, SSA-S, Nikkato Co. Ltd.) under a reducing atmosphere of 97% Ar and 3% H₂, so that Ti dopants will diffuse along the GB plane to form a Ti-diffused GB. After that, we divided this sample into two parts: one is denoted as sample 1 (S1), the other part was annealed in the same furnace in air at 1400°C for 10 h, denoted as sample 2 (S2). The TEM sample with the Ti-diffused GB was prepared at the depth of around 10 μm away from the Ti layer using a dual-beam focused ion beam (FIB) system (Helios G4 UX, FEI). The GB structures and dopants distributions were analyzed by atomic-resolution STEM (JEM ARM200F Cold FE Dual SDD STEM 200kV, JEOL Ltd.) and EDS.

結果と考察 / Results and Discussion

High angle annular dark field (HAADF) STEM observations show that the structural unit of the pristine GB is asymmetric, while that of the GB in S1 is symmetric. These results indicate that a structural transformation was induced by doping. Meanwhile, the GB in S2 shows an asymmetric structural unit, similar to that of the pristine GB. Therefore, annealing in different atmospheres results in the varied GB atomic structures in S1 and S2. Furthermore, the dopants distributions in the GBs were revealed by the atomic resolution EDS mapping. It was found that not only Ti dopants but Ca impurities are also concentrated in the GB. In the GB of S1, both Ti and Ca are concentrated at the center of the seven-membered ring. Ti atoms are also concentrated at the left four columns of the seven-membered ring and the segregation of Ti and Ca are symmetric. In the GB of S2, both Ti and Ca are concentrated more at one part of the GBs than the other part and the segregation of Ti and Ca are asymmetric. These results demonstrate that annealing in the different atmosphere has caused varied GB atomic structures and GB segregation structures in the same GBs.

図・表・数式 / Figures, Tables and Equations

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)

1. Chuchu Yang, The effect of annealing atmospheres on the segregation behaviors in Ti-doped α-Al₂O₃ grain boundary, Journal of the Ceramic Society of Japan, 131, 608-612(2023).
   DOI: 10.2109/jcersj2.23054
   

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

1. C.C. Yang, B. Feng, N. Shibata, Y. Ikuhara. “Atomistic segregation behaviors of Ti in Al2O3 grain boundaries”, 2022 MRS Fall Meeting & Exhibit, 2022年11月28日

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