Structural and magnetic properties of Sm2Fe17-xNbx (x = 0-4) alloys prepared by HDDR processes and their nitrides

Sm2Fe17-xNbxNy (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 Sm2Fe17?xNbx alloys and their nitrides were investigated. It was seen that Sm2(Fe,Nb)17 phase exists in both annealed and HDDR-treated Sm2Fe17?xNbx alloys. However, its content is decreased with the increase in Nb substitution. In annealed alloys, Sm2(Fe,Nb)17 phase becomes unstable and will dissociate into SmFe2 and Fe-rich phases when x > 1.5. With HDDR-treatment, the Nb concentration in recombined Sm2(Fe,Nb)17 phase is decreased, and the content of Fe-rich phases is increased. Sm2Fe17?xNbx 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 Sm2(Fe,Nb)17Ny. Partial Nb atoms in Sm2(Fe,Nb)17Ny phase will be released or excluded by nitrogen atoms. Fe-rich phases increase, and are followed by the amorphous Sm2(Fe,Nb)17Ny phase. Nb substitution for Fe with x = 0.5 and 1.0 in Sm2Fe17?xNbxNy powders increases the coercivity and remanence. But when x is greater than 2.0, Nb substitution will dete- riorate the magnetic properties.