ホーム > 研究活動 > 2019年 > Quantitative identification of constituent phases in a Nd-Fe-B-Cu sintered magnet and temperature dependent change of electron density of Nd2Fe14B studied by synchrotron X-ray diffraction

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Quantitative identification of constituent phases in a Nd-Fe-B-Cu sintered magnet and temperature dependent change of electron density of Nd2Fe14B studied by synchrotron X-ray diffraction

Acta Materialia 181 (2019) 530-536

2019年10月4日(金)

Hiroyuki Okazaki, David Billington, Naruki Tsuji, Wakana Ueno, Yoshinori Kotani, Shogo Kawaguchi, Kunihisa Sugimoto, Kentaro Toyoki, Tomoki Fukagawa,Takeshi Nishiuchi , Kazuhiro Hono, Satoshi Hirosawa, Tetsuya Nakamura

Abstract

We have measured the temperature dependent XRD profiles of anisotropic Nd-Fe-B-Cu sintered magnet during the annealing process. Through Rietveld refinement, we demonstrate the changes in the volume fraction of a Nd2Fe14B main-phase and the other secondary phases as a function of increasing temperature up to 1047°C. The secondary phases mainly included hcp-Nd, fcc-NdOx, and hcp-Nd2O3 at room temperature and fcc-Nd at elevated temperatures. The main phase starts melting above 900°C but remains relatively stable up to 600°C, while the dhcp-Nd phase completely disappears at around 600°C. Taking an advantage of the excellent quality of the XRD profiles in the powdered single crystal sample, we have also investigated the electron density distribution of main phase by MEM/Rietveld analysis in order to elucidate the origin of the large magnetic anisotropy. The change in asymmetric part of electron density is derived by the subtraction of the electron density distributions between those recorded at -123 and -173°C, where the spinreorientation transition at -138°C changes the magneticanisotropy. This change is attributed to be a difference of electron density distribution between Nd f and g sites of the Nd2Fe14B, relatingtothemagneticanisotropy.



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文部科学省

文部科学省
元素戦略プロジェクト(活動紹介)
NIMS磁石パートナーシップ

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合