[T16] Hard Magnetic Materials

[14E-T16-08] In situ TEM Observation of Low Temperature Phase Formation in Mn-Bi Nanopowders Synthesized by Low-Oxygen Induction Thermal Plasma

*J. Wang¹, Y. Hirayama¹, K. Takagi¹ (1.National Institute of Advanced Industrial Science and Technology (AIST), Japan)

Keywords:MnBi, rare-earth-free permanent magnets, In situ TEM observation

The magnetic hard and anisotropic MnBi powders as one of the promising candidates for rare-earth-free permanent magnets were unprecedentedly synthesized with an in-house developed low-oxygen induction thermal plasma (LO-ITP) system. Furthermore, to improve the volume fraction of the desired magnetic hard phase in the final Mn-Bi powders for practical green energy applications, we investigate the origin of the undesired components formation during the processing of Mn-Bi nanopowders through in-situ annealing TEM observation. The results reveal a uniform mixing of Mn and Bi nanopowders in the as-ITP prepared nanopowders. Furthermore, the real-time microstructure evolution and phase transformation indicate that the peritectic reaction initiates at the interface between neighboring Mn and Bi nanopowders, then, followed by the diffusion of Bi into Mn nanopowders. The current mechanism study provides valuable insights for optimizing the production of high-purity MnBi alloy, which is crucial for the development of rare-earth-free permanent magnets and their diverse applications.