Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction

Keisuke Ishigami; Akihiro Yoshinari; Hiroki Iida; Hajime Nakamura; Tetsuya Nakamura; Satoshi Okamoto

doi:10.2320/matertrans.MT-M2025067

Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction

Keisuke Ishigami
, Akihiro Yoshinari
, Hiroki Iida
, Hajime Nakamura
, Tetsuya Nakamura
, Satoshi Okamoto

Research output: Contribution to journal › Article › peer-review

Abstract

The magnetic properties of Nd–Fe–B sintered magnets depend on the secondary phase and its microstructure, which in turn depend on the post-sintering annealing conditions. Therefore, clarifying the correlation between magnetic properties, secondary phases, and annealing conditions is crucial. In this study, we examined the dependence of the formation/decomposition of crystalline phases during the cooling process of Nd–Fe–B sintered magnets containing Ga and C on the heat-treatment temperature using synchrotron radiation high-temperature in situ X-ray diffraction (HT in situ XRD). We also analyzed the correlation between the secondary phase formation/decomposition and magnetic properties. As a result, the existence of a secondary phase that correlated with the magnetic properties was clarified. An exhaustive search was conducted to determine the optimum heat-treatment conditions for the formation of secondary phase correlated with coercivity, thereby demonstrating the usefulness of the HT in situ XRD method in the development of high-performance permanent magnets.

Original language	English
Pages (from-to)	1419-1424
Number of pages	6
Journal	Materials Transactions
Volume	66
Issue number	11
DOIs	https://doi.org/10.2320/matertrans.MT-M2025067
State	Published - 2025
Externally published	Yes

Funding

The synchrotron radiation experiments were performed at the BL02B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal Nos. 2023B1598, 2024A1932, and 2024B1924). This work was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Program: Data Creation and Utilization-Type Material Research and Development Project (Digital Transformation Initiative Center for Magnetic Materials) Grant Number JPMXP1122715503 and NIMS Materials Open Platform for Permanent Magnet.

Keywords

Nd–Fe–B sintered magnets
coercivity
post-sintering annealing
secondary phase
synchrotron radiation high-temperature in situ X-ray diffraction

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10.2320/matertrans.MT-M2025067

Cite this

Ishigami, K., Yoshinari, A., Iida, H., Nakamura, H., Nakamura, T., & Okamoto, S. (2025). Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction. Materials Transactions, 66(11), 1419-1424. https://doi.org/10.2320/matertrans.MT-M2025067

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title = "Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction",

abstract = "The magnetic properties of Nd–Fe–B sintered magnets depend on the secondary phase and its microstructure, which in turn depend on the post-sintering annealing conditions. Therefore, clarifying the correlation between magnetic properties, secondary phases, and annealing conditions is crucial. In this study, we examined the dependence of the formation/decomposition of crystalline phases during the cooling process of Nd–Fe–B sintered magnets containing Ga and C on the heat-treatment temperature using synchrotron radiation high-temperature in situ X-ray diffraction (HT in situ XRD). We also analyzed the correlation between the secondary phase formation/decomposition and magnetic properties. As a result, the existence of a secondary phase that correlated with the magnetic properties was clarified. An exhaustive search was conducted to determine the optimum heat-treatment conditions for the formation of secondary phase correlated with coercivity, thereby demonstrating the usefulness of the HT in situ XRD method in the development of high-performance permanent magnets.",

keywords = "Nd–Fe–B sintered magnets, coercivity, post-sintering annealing, secondary phase, synchrotron radiation high-temperature in situ X-ray diffraction",

author = "Keisuke Ishigami and Akihiro Yoshinari and Hiroki Iida and Hajime Nakamura and Tetsuya Nakamura and Satoshi Okamoto",

note = "Publisher Copyright: {\textcopyright}2025 The Japan Institute of Metals and Materials.",

year = "2025",

doi = "10.2320/matertrans.MT-M2025067",

language = "English",

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Ishigami, K, Yoshinari, A, Iida, H, Nakamura, H, Nakamura, T & Okamoto, S 2025, 'Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction', Materials Transactions, vol. 66, no. 11, pp. 1419-1424. https://doi.org/10.2320/matertrans.MT-M2025067

Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction. / Ishigami, Keisuke; Yoshinari, Akihiro; Iida, Hiroki et al.
In: Materials Transactions, Vol. 66, No. 11, 2025, p. 1419-1424.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction

AU - Ishigami, Keisuke

AU - Yoshinari, Akihiro

AU - Iida, Hiroki

AU - Nakamura, Hajime

AU - Nakamura, Tetsuya

AU - Okamoto, Satoshi

PY - 2025

Y1 - 2025

N2 - The magnetic properties of Nd–Fe–B sintered magnets depend on the secondary phase and its microstructure, which in turn depend on the post-sintering annealing conditions. Therefore, clarifying the correlation between magnetic properties, secondary phases, and annealing conditions is crucial. In this study, we examined the dependence of the formation/decomposition of crystalline phases during the cooling process of Nd–Fe–B sintered magnets containing Ga and C on the heat-treatment temperature using synchrotron radiation high-temperature in situ X-ray diffraction (HT in situ XRD). We also analyzed the correlation between the secondary phase formation/decomposition and magnetic properties. As a result, the existence of a secondary phase that correlated with the magnetic properties was clarified. An exhaustive search was conducted to determine the optimum heat-treatment conditions for the formation of secondary phase correlated with coercivity, thereby demonstrating the usefulness of the HT in situ XRD method in the development of high-performance permanent magnets.

AB - The magnetic properties of Nd–Fe–B sintered magnets depend on the secondary phase and its microstructure, which in turn depend on the post-sintering annealing conditions. Therefore, clarifying the correlation between magnetic properties, secondary phases, and annealing conditions is crucial. In this study, we examined the dependence of the formation/decomposition of crystalline phases during the cooling process of Nd–Fe–B sintered magnets containing Ga and C on the heat-treatment temperature using synchrotron radiation high-temperature in situ X-ray diffraction (HT in situ XRD). We also analyzed the correlation between the secondary phase formation/decomposition and magnetic properties. As a result, the existence of a secondary phase that correlated with the magnetic properties was clarified. An exhaustive search was conducted to determine the optimum heat-treatment conditions for the formation of secondary phase correlated with coercivity, thereby demonstrating the usefulness of the HT in situ XRD method in the development of high-performance permanent magnets.

KW - Nd–Fe–B sintered magnets

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KW - secondary phase

KW - synchrotron radiation high-temperature in situ X-ray diffraction

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ER -

Encompassing Investigation of the Correlation between Secondary Phase Formation, Heat Treatment and Coercivity for Nd–Fe–B Sintered Magnets by in situ High-Temperature Synchrotron X-ray Diffraction

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