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Microstructure and magnetic properties of Nd–Fe–B sintered magnets with P addition

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Abstract

In this paper, the effects of P doping on magnetic properties and microstructure were studied in Nd–Fe–B sintered magnets. With P doping, the grain size gets refined and the distribution of the main phase is optimized due to the reduction of the liquidus temperature. The liquidus temperature for the 0.05 wt% P-doped magnets is 1022 K, while that for the P-free magnets is 1038 K. As P content increases, the liquidus temperature significantly decreases. Clear and continuous grain boundary phases are formed in the P-containing magnets with smaller grain size. The optimized microstructure with average grain size of 8.43 μm is obtained in the 0.05 wt% P-doped magnets, which is approximately 0.69 μm smaller than that of P-free sintered magnets (9.12 μm). Though P is usually thought to be an impurity element, it might be beneficial in Nd–Fe–B sintered magnets with proper addition. The coercivity of the 0.05 wt% P-doped magnets could be increased to 1283 kA·m−1, with slight changes of the remanence and the maximum magnetic energy product. NdPO4 phases in the grain boundary are of hexagonal structure, while those at the triple junctions have monoclinic structure. Activated sintering is achieved by doping proper P element in the Nd–Fe–B sintered magnets.

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Acknowledgements

This study was financially supported by State Key Lab of Advanced Metals and Materials (No. 2018-Z06) and the Fundamental Research Funds for the Central Universities (No. FRF-TP-18-025A1).

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Authors and Affiliations

  1. Institute of Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, 100083, China

    Fang Yang, Ping Li, Cun-Guang Chen & Zhi-Meng Guo

  2. Tianjian Sanhuan Lucky New Materials Inc., Tianjin, 300457, China

    Guang-Le Dong

  3. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083, China

    Yan-Li Sui, Si-Yang Ye & Xue-Xu Gao

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  1. Fang Yang
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Correspondence to Zhi-Meng Guo.

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Yang, F., Dong, GL., Sui, YL. et al. Microstructure and magnetic properties of Nd–Fe–B sintered magnets with P addition. Rare Met. 38, 770–775 (2019). https://doi.org/10.1007/s12598-018-1145-4

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  • DOI: https://doi.org/10.1007/s12598-018-1145-4

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