Magnetic Properties of R2Fe14B Sintered Magnets Substituted 50 at Substitution of Nd with Y and Ce

Abstract

Sintered R2Fe14B (R: rare earth element) magnets with 50 at substitution of Nd by Y and Ce were studied in order to reduce the amount of precious rare earth elements used and to make effective use of the surplus rare earth elements. Nd was substituted with Y for larger magnetization and Ce for higher coercivity. By substituting 50 at% of Nd by Y and Ce with an equiatomic composition, a maximum energy density of 355 kJ/m3 was achieved with the residual flux density of 1.38 T and the coercivity of 533 kA/m as shown in Fig. 1. In order to increase the coercivity, the introduction of R6Fe13Ga grain boundary phase to lead the magnetic separation between grains, which is commonly used for Nd2Fe14B, was studied, however the coercivity was not improved due to a large magnetization of R6Fe13Ga, 0.3 to 0.5 T. By introducing the RFe2 grain boundary phase, the coercivity of 1063 kA/m with the residual flux density of 1.22 T was achieved at the composition of Ce of 40% in the total rare earth elements in R2Fe14B sintered magnet. The magnetization of the RFe2 phase was estimated to be about 0.3 T and was not sufficiently low. Since the RFe2 boundary phase improved the covering of the grains, the magnetic separation was enhanced to increase the coercivity.