Novel microwave assisted chemical synthesis of Nd2Fe14B hard magnetic nanoparticles

The high coercivity and excellent energy product of Nd 2 Fe 14 B hard magnets have led to a large number of high value added industrial applications. Chemical synthesis of Nd 2 Fe 14 B nanoparticles is challenging due to the large reduction potential of Nd 3+ and the high tendency for Nd 2 Fe 14 B oxidation. We report the novel synthesis of Nd 2 Fe 14 B nanoparticles by a microwave assisted combustion process. The process consisted of Nd-Fe-B mixed oxide preparation by microwave assisted combustion, followed by the reduction of the mixed oxide by CaH 2 . This combustion process is fast, energy efficient and offers facile elemental substitution. The coercivity of the resulting powders was ∼8.0 kOe and the saturation magnetization was ∼40 emu g −1 . After removal of CaO by washing, saturation magnetization increased and an energy product of 3.57 MGOe was obtained. A range of magnetic properties was obtained by varying the microwave power, reduction temperature and Nd to Fe ratio. A transition from soft to exchange coupled to hard magnetic properties was obtained by varying the composition of Nd x Fe 1− x B 8 ( x varies from 7% to 40%). This synthesis procedure offers an inexpensive and facile platform to produce exchange coupled hard magnets. Nd 2 Fe 14 B hard magnetic nanoparticles have been produced by a novel microwave based chemical synthesis procedure.