【公開日：2025.06.10】【最終更新日：2025.04.01】

課題データ / Project Data

課題番号 / Project Issue Number

24NM5121

利用課題名 / Title

Advanced materials thermoelectric applications

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）加工・デバイスプロセス/Nanofabrication（副 / Sub）計測・分析/Advanced Characterization

【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）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

熱電材料/ Thermoelectric material,表面・界面・粒界制御/ Surface/interface/grain boundary control,電子顕微鏡/ Electronic microscope,電子回折/ Electron diffraction,スパッタリング/ Sputtering

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)

森 孝雄

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

RAUT Krushna Kumar,CHETTY Raju,NOVITSKII Andrei,SERHIIENKO Illia,TRIVEDI Vikrant,BABA Takahiro,BACK Songyi,CHAUHAN Nagendra Singh,AAMIR Muhammad Fasih,WANG Longquan,LI Airan,Tarachand,SHARMA Anmol,LI Jiankang,WU Xinzhi,WU Gang,HU Zhao

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

NM-649：FE-SEM+EDX [SU8230]
NM-648：FE-SEM+EDX [SU8000]
NM-641：スパッタ装置 [CFS-4EP-LL #2]
NM-226：ショットキー電界放出型走査電子顕微鏡（JSM-7001F）

報告書データ / Report

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

(NM-648, NM-649) Analyzing the microstructural and chemical composition of thermoelectric (TE) materials to understand transport properties. Detection and analysis of the chemical composition and structure of TE materials to understand their properties. (JSM-7001F_NM-641_FE-SEM+EDX+EBSD )Analyzing the microstructural and chemical composition of thermoelectric (TE) materials to understand transport properties. NM-226 ショットキー電界放出型走査電子顕微鏡（JSM-7001F）; Microstructure and compositional studies of Heusler alloys. (NM-641) Deposit a metallic layer on thermoelectric thin films by sputtering to observe thermo-reflectance signals.

実験 / Experimental

(NM-648, NM-649) The microstructure and chemical composition of the TE materials were characterized using SEM-EDX. TE materials were prepared by Ball milling followed by spark plasma sintering. The bulk samples with fracture surfaces were used for microstructure and the metallographic polished samples were used for composition analysis. 
(JSM-7001F _NM- 226_ FE-SEM+EDX+EBSD )  Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy ( SEM-EDS ) was conducted on the polished and fractured surfaces of Sr₁₋ₓSmₓSi₂ samples to examine their composition and morphological characteristics . Tabletop powder diffractometer_Cu_ASC_NC1: The XRD patterns were obtained using an X-ray diffractometer with Cu Kα radiation operating at 40 kV × 15 mA. (NM-226) FE-SEM backscattered images, elemental mapping, and elemental composition were measured using NM-226 Schottky field emission scanning electron microscope (JSM-7001F). The mirror-polished samples were used with an accelerating voltage of 15 kV, and the current ranged from 10 to 12 A. (NM-641) Pt Layer was deposited on thermoelectric thin films by sputtering.

結果と考察 / Results and Discussion

(NM-648) The surface of polished and fractured samples was observed (Figure 1-4), which exhibits the formation of pores. (NM-649) The microstructure analysis revealed the distribution of secondary phases and also the grain size variation with the doping. The elemental composition analysis at the contact layer interfaces of the TE devices was confirmed (Figure 5). 
(JSM-7001F _ NM-  226_  FE-SEM+EDX+EBSD   )  Figure 6 displays SEM images of fractured and polished surfaces from two SPSed samples. These fractured surfaces indicate a high degree of density (~99% relative density) with no significant porosity. The polished surfaces of the samples appear homogeneous, with no observable precipitated phases.
Figure 7 presents orientation maps with colors representing Miller indices. Black spots on the map indicate unresolved areas resulting from high local strains or surface porosity that may have been excluded from the analysis. images in Figures 7(a) and 7(c) show well-crystallized grains that are randomly oriented.Figure 8 shows that an inhomogeneous distribution of elements is apparent, with noticeable Bi-rich regions. Figure 9 shows the fracture morphology of the samples with similar grain sizes.For a systematic study of grain size evolution and uniformity of prepared samples under different synthesis conditions, the samples were examined using the NM-226 (JSM-7001F). In thermoelectric materials, the compositional differences in grain boundaries and within grains significantly impact the transport of heat and charge carriers, thereby directly affecting the performance and efficiency of the materials. Therefore, a precise compositional study using EDX and Backscattered electron SEM images is essential, providing a better understanding of the underlying scattering mechanism in the materials. For Fe2VAl samples, a systematic effect of the synthesis condition on the microstructure has been observed, which enables us to explain the heat/charge carrier scattering (Shown in Figure 10). (NM-641) After this experiment, thermo-reflectance signals were observed from the Pt thin film and heat effusion from Pt layer to the thermoelectric thin films was analyzed.

図・表・数式 / Figures, Tables and Equations

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10 Microscopic study of Fe2VAl prepared at different conditions

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. Tarachand, Effect of magnetic entropy in the thermoelectric properties of Fe-doped Fe2VAl full-Heusler alloy, Materials Today Physics, 48, 101568(2024).
   DOI: 10.1016/j.mtphys.2024.101568
   
2. Andrei Novitskii, Defect Engineering of Bi₂SeO₂ Thermoelectrics, Advanced Functional Materials, 35, (2024).
   DOI: 10.1002/adfm.202416509
   

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

1. 0

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