【公開日：2023.08.01】【最終更新日：2023.05.26】
課題データ / Project Data
課題番号 / Project Issue Number
22KU0105
利用課題名 / Title
Nanostructure analysis in Fe-based alloys by transmission electron microscopy
利用した実施機関 / Support Institute
九州大学
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
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）次世代ナノスケールマテリアル/Next-generation nanoscale materials（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
nanostructure, interface, twin boundary, antiphase boundary
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)
Yongmei M. Jin
所属名 / Affiliation
Michigan Technological University
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
Yuto Tomita
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
Yasukazu Murakami,Tomomazu Yamamoto,Takehiro Tamaoka,Mitsunari Auchi
利用形態 / Support Type
（主 / Main）共同研究/Joint Research（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
KU-006：直交型FIB-SEM
KU-009：ハイコントラスト補助電子顕微鏡
KU-016：低温域観測型・高分解能電子顕微鏡
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Fe-Pd alloys are important magnetic materials relevant to permanent magnet applications due to the high magnetocrystalline anisotropy of their ordered tetragonal L10 phase. While Fe-rich Fe-Pd alloys have been widely investigated, Pd-rich Fe-Pd alloys are relatively unexplored. Importantly, a recent preliminary study of Fe-61.8 at% Pd unveiled fascinating lamellar microstructure of {110} transformation twins of L10 tetragonal orientation variants, where two types of unusual nanoscale interfaces were observed. One is the twin boundaries (TBs) decorated by ordered L12 phase of soft magnetic anisotropy. The other is antiphase boundaries (APBs) within the L10 twin plates which remain straight and perpendicular to the twin boundaries. It is of scientific interest to investigate the local structures and properties of these nanoscale interfaces and understand their effects on the macroscopic magnetic properties of the material. Here we perform a systematic TEM study to examine the TBs and APBs in the lamellar structure of Fe38.2Pd61.8.
実験 / Experimental
The interfaces of the lamellar microstructure in Fe38.2Pd61.8 are studied using different transmission electron microscopy (TEM) techniques, including electron diffraction, dark field (DF) imaging, and annular dark-field scanning transmission electron microscopy (ADF-STEM).
結果と考察 / Results and Discussion
Ordered tetragonal L10 and cubic L12 structures produce different kinds of superlattice reflections. The selected area electron diffraction pattern in Fig. 1(a) demonstrates the presence of those superlattice reflections, which confirms the coexistence of L10 and L12 phases. Three different DF images obtained using (100), (010) and (110) reflections, respectively, show a polytwin structure consisting of alternating L10 plates of two tetragonal variants (TVs), namely TV1 and TV2, with the tetragonal c-axis along [100] and [010], respectively. The plates are parallel to (110) planes. In particular, the (110) DF image in Fig. 1(b) reveals that L12 resides on the TBs, forming a unique two-phase lamellar microstructure. APBs are also clearly observed within the L10 plates, which are perpendicular to the twin boundaries. Both the TBs and APBs are shown to be narrow interfaces of a few nanometers in width. Fig. 1(c) demonstrates atomic column imaging by ADF-STEM from a region that includes a TB (horizontal) and an APB (vertical). Herein, the Pd-rich columns are distinguishable as brighter dots. The L10 tetragonal phase regions show well-defined ordering, as highlighted by the Pd-rich planes in three locations of different TVs and antiphase domains. As shown by the intensity profiles respectively along the line A-B crossing the TB and along the line C-D crossing the APB, the L10-type ordering vanishes in the TB and APB regions. While the L12-type ordering is detected at the twin boundaries, the atomic configuration of the APBs is yet to be determined by energy dispersive X-ray spectroscopy (EDS). The effects of the interfaces on magnetic properties will be investigated using electron holography.
図・表・数式 / Figures, Tables and Equations
FIG. 1. TEM observations along the [001] zone axis. (a) Diffraction pattern where three superlattice spots are highlighted. (b) Darkfield image using the (110) superlattice reflection reveals the locations of L12 phase. (c) ADF-STEM image and the intensity profiles along the line A-B crossing the horizontal TB and the line C-D crossing the vertical APB, which show the interface atomic structures.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
Acknowledgments -Being the collaborators of a joint research project on magnetic Fe-Pd alloys, Mr. Adrian Savovici and Dr. Jerrold A. Floro at the University of Virginia provided the TEM sample for this TEM study.
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)
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