Evolution of microstructure and formation mechanism of Nd-Fe-B nanoparticles prepared by low energy consumption chemical method

Abstract

Nd₂Fe₁₄B nanoparticles were successfully prepared by using a low-energy chemical method. The microscopic characteristics and formation mechanisms of the phases were investigated at each stage during the preparation of Nd-Fe-B nanoparticles. The Nd-Fe-B intermediates, Nd-Fe-B oxides and reduced Nd-Fe-B nanoparticles were detected and analyzed by using TEM, STEM, XRD, SEM, VSM and Rietveld calculations. The results showed that the intermediate of Nd-Fe-B consisted of Fe₃O₄ and Nd and Fe elements surrounded by nitrile organic compounds. The Nd-Fe-B oxide was composed of NdFeO₃ (48.619 wt%), NdBO₃ (31.480 wt%) and α-Fe (19.901 wt%), which was formed by the reaction among Nd, Fe₃O₄ and B₂O₃. NdFeO₃ and NdBO₃ exhibited a perovskite-like lamellar structure, and the grain size was smaller than that of α-Fe. Nd-Fe-B particles were mainly composed of Nd₂Fe₁₄B and α-Fe phases. The small particles of NdFeO₃ and NdBO₃ and the interstitial position between oxide particles and α-Fe were more favorable for the formation of Nd₂Fe₁₄B particles. At the same time, the surface of α-Fe particles can also diffuse to form Nd₂Fe₁₄B nanoparticles. The coercivity of Nd-Fe-B particles was 5.79 kOe and the saturation magnetization was 63.135 emu g^-1.