Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Engineering Materials and Their Applications
Magnetic Properties of Nd–Fe–B Sintered Magnets Produced by Reduction-Grain Boundary Diffusion Process with Heavy Rare-Earths Compounds and Ca Metal Vapor
Masaru UenoharaZheng HanlinHiroaki NishioKen-ichi Machida
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2020 年 61 巻 4 号 p. 782-786


The grain boundary region of NdFeB sintered magnets were modified by reduction-grain boundary diffusion (r-GBD) process using Heavy Rare-Earths (HRE = Dy or Tb) metal which generated via reduction of HRE compounds such as oxide or fluoride with Ca metal vapor. After modification, magnetic properties were measured accurately by superconducting magnet-based vibrating sample magnetometer (SCM-VSM). The coercivity of DyF3 and TbF3 treated magnets with the assistance of reduction by Ca metal vapor (HcJ = 1451 kA/m and 1778 kA/m, respectively) were effectively enhanced compared to untreated magnets (HcJ = 1003 kA/m) without severe decreasing of remanence value. The resultant coercivity was higher than that of the magnets modified with DyF3 (HcJ = 1319 kA/m) and TbF3 (HcJ = 1580 kA/m) without using any reducing agent such as Ca metal vapor.

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