Rare Metals

, Volume 39, Issue 1, pp 36–40 | Cite as

Phase composition and magnetic properties of Pr–Nd–MM–Fe–B nanocrystalline magnets prepared by spark plasma sintering

  • Xin Wang
  • Zeng-Ru Zhao
  • Fei Liu
  • Yan-Li Liu
  • Gao-Feng Wang
  • Ming-Gang ZhuEmail author
  • Xue-Feng ZhangEmail author


The isotropic nanocrystalline [(PrNd)0.8MM0.2]29.8Fe68.7Al0.1Cu0.12Co0.88B magnets (MM: mischmetal) were prepared by single-main phase and double-main phase methods using spark plasma sintering (SPS). Melt-spinning method was used to prepare initial powder and avoid component deviations caused by longtime ball milling. The magnetic properties of the magnet prepared by double-main phase method (called double-main phase magnet, DMP magnet) are remanence of Br = 0.75 T, intrinsic coercivity of Hcj = 909.83 kA·m−1, maximum magnetic energy product of (BH)max = 95.48 kJ·m−3, which are better than those of the magnet prepared by single-main phase method (called single-main phase magnet, SMP magnet). The diffraction peaks of the main phase of DMP magnet split in X-ray diffractometer (XRD) pattern, indicating that R2Fe14B phases with different distributions of La/Ce elements exist in the magnet. This speculation is confirmed by transmission electron microscopy (TEM) observation. The La/Ce-rich main phase and La/Ce-lean main phase are present in DMP magnets. The heterogeneity of rare earth elements suppresses the magnetic dilution effect in DMP magnet, and the magnetic properties are improved. Though the DMP magnet contains different main phases, it presents unitary Curie temperature (TC) of 577 K, which is higher than that of SMP magnet. This result suggests that the TC of the magnets can be promoted by double-main phase method and SPS.


Mischmetal Double-main phase Spark plasma sintering Magnetic properties Microstructure 



This work was financially supported by the National Key Research and Development Program of China (No. 2016YFB0700903) and the National Natural Science Foundation of China (Nos. 51571064 and 51571126).


  1. [1]
    Sagawa M, Fujimura S, Togawa N, Yamamoto H, Matsuura Y. New material for permanent magnets on a base of Nd and Fe. J Appl Phys. 1984;55(6):2083.CrossRefGoogle Scholar
  2. [2]
    Bai G, Gao RW, Sun Y, Han GB, Wang B. Study of high-coercivity sintered NdFeB magnets. J Magn Magn Mater. 2007;308(1):20.CrossRefGoogle Scholar
  3. [3]
    Li JJ, Guo CJ, Zhou TJ, Qi ZQ, Yu X, Yang B, Zhu MG. Effects of diffusing DyZn film on magnetic properties and thermal stability of sintered NdFeB magnets. J Magn Magn Mater. 2018;454:215.CrossRefGoogle Scholar
  4. [4]
    Zhang XF, Zhang WK, Li YF, Liu YL, Li ZB, Ma Q, Shi MF, Liu F. Magnetic properties of melt-spun MM–Fe–B ribbons with different wheel speeds and mischmetal contents. Rare Met. 2017;36(12):992.CrossRefGoogle Scholar
  5. [5]
    Sagawa M, Fujimura S, Yamamoto H, Matsuura Y, Hiraga K. Permanent magnet materials based on the rare earth–iron–boron tetragonal compounds. IEEE Trans Magn. 1984;20(5):1584.CrossRefGoogle Scholar
  6. [6]
    Ma TY, Yan M, Wu KY, Wu B, Liu XL, Wang XJ, Qian ZY, Wu C, Xia WX. Grain boundary restructuring of multi-main-phase Nd–Ce–Fe–B sintered magnets with Nd hydrides. Acta Mater. 2018;142:18.CrossRefGoogle Scholar
  7. [7]
    Li ZB, Shen BG, Zhang M, Hu FX, Sun JR. Substitution of Ce for Nd in preparing R2Fe14B nanocrystalline magnets. J Alloys Compd. 2015;628:325.CrossRefGoogle Scholar
  8. [8]
    Herbst JF. R2Fe14B materials: intrinsic properties and technological aspects. Rev Mod Phys. 1991;63(63):819.CrossRefGoogle Scholar
  9. [9]
    Alam A, Khan M, McCallum RW, Johnson DD. Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets. Appl Phys Lett. 2013;102(4):4176.CrossRefGoogle Scholar
  10. [10]
    Alam A, Johnson DD. Mixed valency and site-preference chemistry for cerium and its compounds: a predictive density-functional theory study. Phys Rev B. 2014;89(23):2495.CrossRefGoogle Scholar
  11. [11]
    Yan CJ, Guo S, Chen RJ, Liu J, Lee D, Yan AR. Effect of Ce on the magnetic properties and microstructure of sintered didymium–Fe–B magnets. IEEE Trans Magn. 2014;50(10):1.CrossRefGoogle Scholar
  12. [12]
    Pathak AK, Khan M, Gschneidner KA, McCallum RW, Zhou L, Sun K, Dennis KW, Zhou C, Pinkerton FE, Kramer MJ, Pecharsky VK. Cerium: an unlikely replacement of dysprosium in high performance Nd–Fe–B permanent magnets. Adv Mater. 2015;27(16):2663.CrossRefGoogle Scholar
  13. [13]
    Yang MN, Wang H, Hu YF, Yang LYM, Aimee M, Yang B. Relating atomic local structures and Curie temperature of NdFeB permanent magnets: an X-ray absorption spectroscopic study. Rare Met. 2018;37(11):983.CrossRefGoogle Scholar
  14. [14]
    Jin JY, Zhang YJ, Bai GH, Qian ZY, Wu C, Ma TY, Shen BG, Yan M. Manipulating Ce valence in RE2Fe14B tetragonal compounds by La–Ce co-doping: resultant crystallographic and magnetic anomaly. Sci Rep. 2016;6:30194.CrossRefGoogle Scholar
  15. [15]
    Zhu MG, Li W, Wang JD, Zheng LY, Li YF, Zhang K, Feng HB, Liu T. Influence of Ce content on the rectangularity of demagnetization curves and magnetic properties of Re–Fe–B magnets sintered by double main phase alloy method. IEEE Trans Magn. 2014;50(1):1000104.Google Scholar
  16. [16]
    Gong W, Hadjipanayis GC. Misch-metal-iron based magnets. J Appl Phys. 1988;63(8):3513.CrossRefGoogle Scholar
  17. [17]
    Zhu MG, Han R, Li W, Huang SL, Zheng DW, Song LW, Shi XN. An enhanced coercivity for (CeNdPr)–Fe–B sintered magnet prepared by structure design. IEEE Trans Magn. 2015;51(11):2014604.Google Scholar
  18. [18]
    Jin JY, Ma TY, Zhang YJ, Bai GH, Yan M. Chemically inhomogeneous RE–Fe–B permanent magnets with high figure of merit: solution to global rare earth criticality. Sci Rep. 2016;6:32200.CrossRefGoogle Scholar
  19. [19]
    Fan XD, Guo S, Chen K, Chen RJ, Lee D, You CY, Yan AR. Tuning Ce distribution for high performance Nd–Ce–Fe–B sintered magnets. J Magn Magn Mater. 2016;419:394.CrossRefGoogle Scholar
  20. [20]
    Tang J, Yang LR, Zhang L, Wei CF, Mei Y, Wen YG. Succession law of Nd–Fe–B alloys with different coercivities. Rare Met. 2015;34(9):657.CrossRefGoogle Scholar
  21. [21]
    Lai RS, Chen RJ, Yin WZ, Tang X, Wang ZX, Jin CX, Lee D, Yan AR. High performance (La, Ce, Pr, Nd)–Fe–B die-upset magnets based on misch-metal. J Alloys Compd. 2017;724:275.CrossRefGoogle Scholar
  22. [22]
    Niu E, Chen ZA, Chen GA, Zhao YG, Zhang J, Rao XL, Hu BP, Wang ZX. Achievement of high coercivity in sintered R–Fe–B magnets based on mischmetal by dual alloy method. J Appl Phys. 2014;115(11):113912.CrossRefGoogle Scholar
  23. [23]
    Xiong JF, Shang RX, Liu YL, Zhao X, Zuo WL, Hu FX, Sun JR, Zhao TY, Chen RJ, Shen BG. Magnetic properties of misch-metal partially substituted Nd–Fe–B magnets sintered by dual alloy method. Chin Phys B. 2018;27(7):077504.CrossRefGoogle Scholar
  24. [24]
    Lu QM, Niu J, Liu WQ, Yue M, Altounian Z. Enhanced magnetic properties of spark plasma sintered (La/Ce)–Fe–B magnets. IEEE Trans Magn. 2017;53(11):2100603.CrossRefGoogle Scholar
  25. [25]
    Yue M, Zhang JX, Xiao YF, Wang GP, Li T. New kind of NdFeB magnet prepared by spark plasma sintering. IEEE Trans Magn. 2003;39(6):3551.CrossRefGoogle Scholar
  26. [26]
    Chu LH, Liu Y, Li J, Ma YL, Li CY. Structural and magnetic study of hot-pressed and hot-deformed Nd13.5−xCexFe80.4Ga0.5B5.6 (x = 0, 0.5, 1) prepared by spark plasma sintering. IEEE Trans Magn. 2012;48(6):2092.CrossRefGoogle Scholar
  27. [27]
    Ma YL, Liu Y, Li J, Du HL, Gao J. Anisotropic nanocomposite Nd2Fe14B/α-Fe magnets prepared by spark plasma sintering. IEEE Trans Magn. 2009;45(6):2605.CrossRefGoogle Scholar
  28. [28]
    Yue M, Zhang JX, Tian M. Microstructure and magnetic properties of isotropic bulk NdxFe94−xB6 (x = 6, 8, 10) nanocomposite magnets prepared by spark plasma sintering. J Appl Phys. 2006;99(8):601.Google Scholar
  29. [29]
    Zhao W, Liu Y, Li J, Wang RQ, Qiu YC. Microstructure and magnetic properties of hot-deformed anisotropic Nd–Fe–B magnets prepared from amorphous precursors with different crystallization proportions. Rare Met. 2017;36(4):268.CrossRefGoogle Scholar
  30. [30]
    Huang YL, Liu ZW, Zhong XC, Yu HY, Zeng DC. NdFeB based magnets prepared from nanocrystalline powders with various compositions and particle sizes by spark plasma sintering. Powder Metall. 2012;55(2):124.CrossRefGoogle Scholar

Copyright information

© The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Division of Functional MaterialsCentral Iron and Steel Research InstituteBeijingChina
  2. 2.School of ScienceInner Mongolia University of Science and TechnologyBaotouChina
  3. 3.Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal ResourcesInner Mongolia University of Science and TechnologyBaotouChina

Personalised recommendations