Preparation of Sm2Fe17−xGaxNy/Cy magnets by a hydrogenation-disproportionation-desorption-recombination process

A hydrogenation-disproportionation-desorption-recombination process (HDDR) was applied to Sm2Fe17−xGax (x=0.5, 1, and 2). The process was studied by means of temperature-pressure analysis, x-ray diffraction and scanning electron microscopy. It was shown that Ga not only stabilizes the interstitially modified compounds Sm2Fe17−xGaxCy (0<y<3) but it also stabilizes the parent compound Sm2Fe17−xGax against the disproportionation by hydrogen. Therefore, only for x=0.5 can a nearly complete HDDR be performed. The HDDR-treated and subsequently nitrogenated or carburized samples show coercivities μ0JHC up to 3.1 T and 2.5 T, respectively. Hot compaction increases the density of the Sm2Fe16.5Ga0.5Cy powder; however, it leads to a loss of coercivity due to decomposition into α-iron and samarium carbides.