Effects of Grain Boundary Phase on Coercivity of Dysprosium-Free Rare Earth Magnet

Enokido, Yasushi; Miwa, Masashi; Goto, Syota; Fujikawa, Yoshinori

doi:10.2320/matertrans.m2016160

Cited by 43 publications

(5 citation statements)

References 9 publications

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“…The particle oxidization in the PVA granules reduced the content of the R-rich phase and prevented sintering of the liquid phase; 19) it can also explain their low magnetic coercivity. 20,21) Both granule types possessed extremely low values of the residual flux density, which was proportional to the relative density (ratio of actual to theoretical density) and degree of orientation. The PVB granules with high sintered density also exhibited a low residual magnetic flux density, which was likely caused by the low degree of orientation because the particle bonding by the organic binder prevented the rotation of the primary particles against the applied magnetic field during pressing.…”

Section: Binder-bound Granulesmentioning

confidence: 99%

Magnetic Properties and Particle Flowability of Neodymium Magnetic Granules

2021

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In this study, sintered NdFeB magnets with high residual flux densities and magnetic coercivities were manufactured by filling a die cavity with granulated NdFeB magnetic powder during pressing. In the binder-bound granules prepared by a spray drying method, the bonding force between the primary particles was relatively strong. However, the magnets obtained from these granules could not achieve high residual magnetic flux densities because it was difficult to align each particle in these granules along the magnetization easy axis through magnetic field pressing. Therefore, a weak liquid bridge force was utilized for particle binding. After preparing the liquid-bound granules containing 0.25 mass% terpineol, which does not evaporate easily at room temperature (³293 K) but undergoes debinding on baking, the angle of repose of the magnetic powder (representing its flowability index) decreased from 63°to 44.2°, while the deterioration of its magnetic properties was considerably suppressed. As a result, the residual magnetic flux density of the sintered magnet was equal to 99.3% of the value obtained for the non-granulated powder. In addition, the liquid-bound granules exhibited high filling rates and low weight variations, demonstrating their applicability for mass production.

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Section: Binder-bound Granulesmentioning

confidence: 99%

Magnetic Properties and Particle Flowability of Neodymium Magnetic Granules

2021

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“…Alloying Ga in some specific cases is reported to result in improvements in coercivity via formation of all nonferromagnetic grain boundary phases including a relatively Fe-rich Nd 6 Fe 13 Ga-type phase that is non-ferromagnetic at room temperature and above [29]- [31]. Unfortunately, this phase forms as a relatively thick intergranular phase (ca., 20 nm thick in comparison to 2 nm in the conventional sintered magnets) by consuming a part of Nd 2 Fe 14 B, resulting in a decrease in saturation magnetization.…”

Section: B Nd-fe-b Beyond Nd-dy-fe-bmentioning

confidence: 99%

Permanent Magnets Beyond Nd-Dy-Fe-B

Hirosawa

2019

IEEE Trans. Magn.

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Provision of a concise summary of recent developments of permanent magnet materials and the materials science underlining them toward realizing permanent magnets beyond the current Nd-Dy-Fe-B is attempted, and approaches to solving the remaining fundamental issues are discussed. Focused are two promising groups of materials: the ThMn 12 -type Fe-rich Sm(Fe 1−x Co x ) 12based materials and the Nd 2 Fe 14 B-based materials. Materials science based on atomistic view of permanent magnet materials specifically developed for this purpose is required in order to break into a precise control of the microstructure in atomic levels with the aid of computational material engineering. Atomistic understandings of coercivity mechanism and differences in free energy associated with formation of non-equilibrium structures such as grain boundaries and interfaces with sub-phases are proposed to be essential.

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“…[17][18][19][20] Recently, the Nd-Fe-B magnets prepared from Nd-rich Ga-doped Nd-Fe-B strip cast flakes have become an important object of research. [21,22] In these Ga-doped magnets, continuous GB phases were formed which brings out the isolated intergrain exchange coupling. Note that unlike the conventional magnets, these significant changes in microstructure and coercivity of Ga-doped magnets are accompanied by the formation of anti-ferromagnetic RE 6 Fe 13 Ga (RE = Pr, Nd) phase after the annealing process.…”

Section: Introductionmentioning

confidence: 99%

Effects of post-sinter annealing on microstructure and magnetic properties of Nd–Fe–B sintered magnets with Nd–Ga intergranular addition*

Zhu¹,

Jin²,

Jin³

et al. 2021

Chinese Phys. B

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We investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd–Fe–B sintered magnets with different quantities of Nd–Ga intergranular additions. The magnet with fewer Nd–Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd–Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd–Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin grain boundary phase in the magnets with an appropriate Nd–Ga concentration after the annealing process. However, the exceeding Nd–Ga addition brings out notable segregation of grain boundary phase, and prior formation of part RE 6Fe13Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process. Therefore, the diverse changes of magnetic properties with different Nd–Ga concentrations are based on the respective evolution of grain boundary after the annealing process.

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Effects of Grain Boundary Phase on Coercivity of Dysprosium-Free Rare Earth Magnet

Cited by 43 publications

References 9 publications

Magnetic Properties and Particle Flowability of Neodymium Magnetic Granules

Magnetic Properties and Particle Flowability of Neodymium Magnetic Granules

Permanent Magnets Beyond Nd-Dy-Fe-B

Effects of post-sinter annealing on microstructure and magnetic properties of Nd–Fe–B sintered magnets with Nd–Ga intergranular addition*

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