Structural and magnetic properties of Sm_2Fe_(17-x)Nb_x (x = 0-4) alloys prepared by HDDR processes and their nitrides

摘要

Sm_2Fe_(17-x)Nb_xN_y, (x = 0-4) powder was synthesized by HDDR treatment and nitrogenation. The effects of partial Nb substitution for Fe on the structural and magnetic properties of Sm_2Fe_(17-x)Nb_x alloys and their nitrides were investigated. It was seen that Sm_2(Fe,Nb)_(17) phase exists in both annealed and HDDR-treated Sm_2Fe_(17-x)Nb_x alloys. However, its content is decreased with the increase in Nb substitution. In annealed alloys, Sm_2(Fe,Nb)_(17) phase becomes unstable and will dissociate into SmFe_2 and Fe-rich phases when x > 1.5. With HDDR-treatment, the Nb concentration in recombined Sm_2(Fe,Nb)_(17)N_y phase is decreased, and the content of Fe-rich phases is increased. Sm_2Fe_(17-x)Nb_x powder exhibits dendritic cracks and fine particles with a size of less than 300 nm. In nitrogenated alloys, N atoms mainly enter 2:17-type phase to form Sm_2(Fe,Nb)_(17)N_y,. Partial Nb atoms in Sm_2(Fe,Nb)_(17)N_y phase will be released or excluded by nitrogen atoms. Fe-rich phases increase, and are followed by the amorphous Sm_2(Fe,Nb)_(17)N_y phase. Nb substitution for Fe with x = 0.5 and 1.0 in Sm_2Fe_(17-x)Nb_xN_y powders increases the coercivity and remanence. But when x is greater than 2.0, Nb substitution will deteriorate the magnetic properties.