Structure, nitridation efficiency and magnetic properties of SmFe powders and its nitrides

• Published in: Rare metals 2023-06, Vol.42 (6), p.1983-1988
• Main Authors: Chen, Xiao-Xia, Luo, Yang, Hu, Zhou, Yan, Wen-Long, Quan, Ning-Tao, Lu, Shuo, Yu, Dun-Bo, Xie, Jia-Jun
• Format: Article
• Language: English
• Subjects: Annealing; Biomaterials; Chemistry and Materials Science; Coercivity; Energy; Magnetic properties; Materials Engineering; Materials Science; Melt spinning; Metallic Materials; Nanoscale Science and Technology; Nitrides; Physical Chemistry; Remanence; Surface defects
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-017-0943-4

The effect of annealing temperature ( T A ) at 600–900 °C on structure and magnetic properties of the melt-spun Sm 8.6 Fe 85.9 Co 4.3 Zr 1.2 alloys and its nitrides was investigated. Results show that the melt-spun powder is TbCu 7 -type SmFe 9 single phase. X-ray diffractometer (XRD) Rietveld refinement shows that the lattice parameter a increases, c and c/a decrease with the increase in T A at 600–700 °C. This is due to the tendency of nitrogen entering into the 3f site (1/2, 0, 0) during the nitridation process, which is good for the magnetic properties. The phase transforms from TbCu 7 -type SmFe 9 to Th 2 Zn 17 -type Sm 2 Fe 17 at above 800 °C. Scanning electron microscopy (SEM) images show that the amount of surface defects of melt-spun powder which are harmful for magnetic properties decreases at first and then increases as T A increases. The coercivity ( H cj ) and maximum magnetic energy product (( BH ) max ) of its nitrides increase first and then decrease as a function of T A . And the remanence ( B r ) always shows a decrease. The optimal magnetic properties of H cj  = 748 kA·m −1 , B r  = 0.92 T, ( BH ) max  = 118 kJ·m −3 are obtained by annealing at 675 °C for 2 h and then nitriding at 460 °C for 10 h.