| 简介 |
PROBLEM TO BE SOLVED : To provide a rare earth sintered magnet improved in corrosion resistance.
SOLUTION : A rare earth sintered magnet comprises : main phases each of which includes an R2T14B phase in which a composition of crystal grains is represented by a composition formula R2T14B, where R denotes one or more rare earth elements including Nd, T denotes Fe or one or more transition metal elements including Fe and Co, and B denotes B or B and C; a grain boundary phase having more R than the R2T14B phase; and a grain boundary triple point surrounded by three or more of the plural main phases. The grain boundary triple point includes : an R rich phase including 90 atom% or more of R; and an R75 phase in which R is 60 atom% or more and 90 atom% or less and which includes Co and Cu. In the grain boundary triple point, a composition ratio (Co+Cu)/R represented by converting R, Co and Cu included in the R75 phase into atomic percentages satisfies the following equation. And within a cross section area of the grain boundary triple point in its cross section, an area in which both a Co-rich region and a Cu-rich region are coincident with each other is 60% or more. 0.05≤(Co+Cu)/R<0.5...(1)
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