Influence of silicon and carbon elements on formation of 1:13 phase and microstructure in LaFe13-ySiy compounds

Microstructure dependent on silicon and formation of 1:13 phase in LaFe_13–ySi_yC_0.2 compounds was investigated. C and Si elements played different roles in assisting the formation of 1:13 phase. Si could inhibit the growth of α-Fe. The volume fraction of La-rich phase increased with the increase of Si content in the LaFe_13–ySi_yC_0.2 ingots. When Si content was lower in LaFe_13–ySi_yC_0.2 (y≤1.0), α-Fe was excess and grew very large in the initial annealing process. As a result, a large amount of α-Fe remained even after a long time annealing process. Carbon doping could accelerate the formation of 1:13 phase in the LaFe_13–ySi_yC_0.2 compounds. The amount of the 1:13 phase reached ～90 vol.% in LaFe_13–ySi_yC_0.2 (y≥1.2) after annealing at 1353 K for only 3 d. After optimized annealing, large magnetic entropy changes were obtained in LaFe_13–ySi_yC_0.2 compounds (18.6 and 15 J/(kg·K) in 0–2 T field change for y=1.2, 1.4, respectively).