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Fabrication of High-performance Sm–Fe–N isotropic bulk magnets by a combination of High-pressure compaction and current sintering

TbCu7-type Sm–Fe–N coarse powders in the flake form were consolidated without a bonding medium using a low-thermal-load process of current sintering combined with high-pressure compression. When compacted at 1.2GPa, the relative density of the powder was increased by 80% with close stacking of the f...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2012-04, Vol.324 (7), p.1337-1341
Main Authors: Takagi, Kenta, Nakayama, Hiroyuki, Ozaki, Kimihiro, Kobayashi, Keizo
Format: Article
Language:English
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Summary:TbCu7-type Sm–Fe–N coarse powders in the flake form were consolidated without a bonding medium using a low-thermal-load process of current sintering combined with high-pressure compression. When compacted at 1.2GPa, the relative density of the powder was increased by 80% with close stacking of the flake particles. Although the subsequent current heating was only briefly performed at a low temperature of 400°C to avoid decomposition, the compact was consolidated into a rigid bulk in which the particles were bonded at the atomic level. Finally, by using cyclic compaction, this process produced bulk magnets with a density of 92% that exhibited the highest maximum energy product (BH)max of 16.2MGOe, which surpasses that of conventional isotropic Sm–Fe–N bond magnets. ► We conduct a consolidation of Sm1Fe7N bulk magnets without thermal decomposition. ► Rapid current sintering with high-pressure compaction is used as a low-thermal-load process. ► In this process, sintering occurs at a temperature of 400°C, which is below the decomposition point. ► As a result, bulk magnets with a density of over 92% are obtained without decomposition. ► These magnets exhibit the highest (BH)max (16.2MGOe) among isotropic Sm–Fe–N magnets.
ISSN:0304-8853
DOI:10.1016/j.jmmm.2011.11.035