Understanding the element segregation and phase separation in the Ce-substituted Nd-(Fe,Co)-B based alloys

Zhao, Lizhong; Zhang, J. S.; Ahmed, Gulzar; Liao, Xuefeng; Liu, Zhongwu; Grenèche, Jean‐Marc

doi:10.1038/s41598-018-25230-0

Cited by 27 publications

(6 citation statements)

References 33 publications

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“…Similar jump was also observed in volume near 50at.%Re, which indicates towards possible phase change. Moreover, the existence of mixed valency in Ce, e.g., trivalent (+3) and tetravalent (+4), can also lead to the phase change in Ce-Fe compounds, for example, smaller Ce 4+ ion radii compared to Ce 3+ makes it easier to form the CeFe 2 phase [96]. Mixed valence state, and the fact that the ground state structure of CeFe 2 is not cubic, increases the challenge of accounting it into ML models, therefore, for simplicity, not considered.…”

Section: Effects Of Chemical Mixing Of 3d and 4d/5d Transition Metals...mentioning

confidence: 99%

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

Singh,

Del Rose,

Vazquez

et al. 2022

Preprint

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We employ a descriptor based machine-learning approach to assess the effect of chemical alloying on formationenthalpy of rare-earth intermetallics. Application of machine-learning approaches in rare-earth intermetallic design have been sparse due to limited availability of reliable datasets. In this work, we developed an 'in-house' rare-earth database with more than 600+ compounds, each entry was populated with formation enthalpy and related atomic features using high-throughput density-functional theory (DFT). The SISSO (sure independence screening and sparsifying operator) based machine-learning method with meaningful atomic features was used for training and testing the formation enthalpies of rare earth compounds. The complex lattice function coupled with the machine-learning model was used to explore the effect of transition metal alloying on the energy stability of Ce based cubic Laves phases (MgCu 2 type). The SISSO predictions show good agreement with high-fidelity DFT calculations and X-ray powder diffraction measurements. Our study provides quantitative guidance for compositional considerations within a machine-learning model and discovering new metastable materials. The electronic-structure of Ce-Fe-Cu based compound was also analyzed in-depth to understand the electronic origin of phase stability. The interpretable analytical models in combination with density-functional theory and experiments provide a fast and reliable design guide for discovering technologically useful materials.

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Section: Effects Of Chemical Mixing Of 3d and 4d/5d Transition Metals...mentioning

confidence: 99%

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

Singh,

Del Rose,

Vazquez

et al. 2022

Preprint

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“…[19] The Curie temperature of the NdFe 2 phase has been estimated to be 340 K by neutron measurements, thus the increasing Nd content in the 1:2 phase tends to change the Nd/Ce fraction in REFe 2 phase. To demonstrate this effect, [45] 2 mm (Nd 1−x Ce x ) 25 Fe 40 Co 20 Al 4 B 11 (x = 0.1-0.5) rods with a high fraction of the 1:2 phase were prepared by mold casting method. [45] The corresponding room temperature Mössbauer spectra illustrated in Fig.…”

Section: Refe 2 Phasementioning

confidence: 99%

“…To demonstrate this effect, [45] 2 mm (Nd 1−x Ce x ) 25 Fe 40 Co 20 Al 4 B 11 (x = 0.1-0.5) rods with a high fraction of the 1:2 phase were prepared by mold casting method. [45] The corresponding room temperature Mössbauer spectra illustrated in Fig. 13 clearly show the presence of a quadrupolar component corresponding to the 1:2 phase (pink), indicating its paramagnetism.…”

Section: Refe 2 Phasementioning

confidence: 99%

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⁵⁷Fe Mössbauer spectrometry: A powerful technique to analyze the magnetic and phase characteristics in RE–Fe–B permanent magnets*

et al. 2021

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This review summarizes the recent advances on the application of 57Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce2Fe14B, (Ce, Nd)2Fe14B and MM2Fe14B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting ΔE Q of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field B hf increases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the 57Fe Mössbauer spectrometry due to its high sensitivity. On this basis, the content, magnetic behavior, and magnetization of the REFe2 phase, the amorphous grain boundary (GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.

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“…Recently, chemically heterogeneous multi-main-phase (MMP) Nd-Ce-Fe-B magnets attract considerable research interest due to their superior magnetic performance [9,10]. This MMP morphology can be obtained not only in sintered microcrystalline Nd-Ce-Fe-B magnets but also in nanocrystalline Nd-Ce-Fe-B alloys prepared by melt-spinning [11,12]. The sintered binary-main-phase (BMP) Nd-Ce-Fe-B magnets can be fabricated by co-sintering of two distinct powders, Nd-Fe-B and Nd-Ce-Fe-B, via a conventional powder metallurgy route [13].…”

Section: Introductionmentioning

confidence: 99%

Micromagnetic simulation of microstructure effect for binary-main-phase Nd–Ce–Fe–B magnets

Kim¹,

Liang²,

Han³

et al. 2021

J. Phys.: Condens. Matter

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We investigate the magnetic properties of a chemically heterogeneous binary-main-phase (BMP) Nd–Ce–Fe–B magnet with a core–shell structure via micromagnetic simulation. It is found that the coercivity strongly depends on the shell thickness. The BMP magnet’s coercivity initially increases and then decreases with increasing Nd-rich shell thickness, and so there is the optimal shell thickness which shows the maximum coercivity for any given Ce concentration. The simulation shows the significant difference in coercivity and maximum energy product between the BMP and single-main-phase magnets. Notably, the magnetization reversal mechanism of the BMP magnet is revealed in the simulation. Local reversals in the BMP magnet first occur in the Ce-rich shells, followed by the Nd-rich cores. Then, the magnetization in Ce-rich core/Nd-rich shell typed grains is switched after reversed magnetization of all the Nd-rich core/Ce-rich shell typed grains. The BMP magnet represents a further increased coercivity for a larger GB thickness, which can be well explained by a maximum stray field.

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Understanding the element segregation and phase separation in the Ce-substituted Nd-(Fe,Co)-B based alloys

Cited by 27 publications

References 33 publications

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

⁵⁷Fe Mössbauer spectrometry: A powerful technique to analyze the magnetic and phase characteristics in RE–Fe–B permanent magnets*

Micromagnetic simulation of microstructure effect for binary-main-phase Nd–Ce–Fe–B magnets

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Understanding the element segregation and phase separation in the Ce-substituted Nd-(Fe,Co)-B based alloys

Cited by 27 publications

References 33 publications

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

Machine-learning enabled thermodynamic model for the design of new rare-earth compounds

57Fe Mössbauer spectrometry: A powerful technique to analyze the magnetic and phase characteristics in RE–Fe–B permanent magnets*

Micromagnetic simulation of microstructure effect for binary-main-phase Nd–Ce–Fe–B magnets

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⁵⁷Fe Mössbauer spectrometry: A powerful technique to analyze the magnetic and phase characteristics in RE–Fe–B permanent magnets*