Synthesis mechanism of Sm2Fe17 alloy produced in reduction-diffusion process

Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials. Reduction-diffusion (R/D) method was a new preparation process for the Sm2Fe17 alloy, and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds. In this text, thermodynamics and kinetics for the synthesis of the Sm2Fe17 alloy by reduction-diffusion (R/D) method in the Ca-Sm2O3-Fe system were analyzed. The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope (SEM). The results showed that the thickness of the Sm2Fe17 alloy layer versus the reaction time could be fit by the parabola law, and its growth model was determined to be: (L0-L)2=43.848 t, the diffusion of Sm into Fe proceeded with the formation of the Sm2Fe17 phase from the very beginning of the reaction, and rich samarium phases, such as SmFe2 and SmFe3, were not formed, and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.