Preparation of TbCu7-type Sm-Fe powders by low-temperature HDDR treatment

Low-temperature hydrogen-disproportionation-desorption-recombination (HDDR) treatment of Sm-Fe alloy powder was conducted to prepare a metastable TbCu7 type Sm-Fe alloy powder with a grain size of more than a few hundreds of nanometers. While a treatment temperature above 700 degrees C produced the familiar Th2Zn17 type alloy, one below 600 degrees C resulted in successful synthesis of the TbCu7 type Sm-Fe alloy with submicron-size grains. This TbCu7 type alloy powder, however, showed no significant improvement in magnetic properties compared to the Th2Zn17 type, as its composition was estimated to be near SmFe8.5 and thus did not achieve the expected Fe-rich composition. Therefore, cross-sectional transmission electron microscope observation of the unfinished TbCu7 type alloy powder was conducted in order to explore means of forming the Fe-rich phase. (C) 2018 Elsevier B.V. All rights reserved.