Patent ID: 7988795
Filing Date: 2011-08-02
Classification: H01F

Abstract:
1. An R-T-B-C rare earth sintered magnet wherein R is at least one rare earth element selected from the group consisting of Ce, Pr, Nd, Tb, and Dy, T is iron or a mixture of iron and at least one other transition metal, B is boron, and C is carbon, which magnet is obtained by: mixing (II) 1 to 20% by weight of an R-rich R-T-B—C sintering aid alloy consisting essentially of 50 wt %≦R≦65 wt %, 0.3 wt %≦B≦0.9 wt %, 0.01 wt %≦C≦0.5 wt %, 0.1 wt %≦Al≦1.0 wt %. 0.1 wt %≦Cu≦5.0 wt %, and the balance of T, (III) 10 to 50% by weight of an R—O pulverizing the mixture through a jet mill in a nitrogen stream to an average particle size of 0.01 to 30 μm, compacting the mixture in a magnetic field into a compact, sintering and heat treating the compact, wherein the rare earth sintered magnet has a sintered structure consisting of an R said grain boundary phase consisting essentially of 40 to 98% by volume (a volume fraction in the grain boundary phase) of R-O