Microstructure, phase evolution and magnetocaloric properties of LaFe11.6Si1.4/La70Co30 composite

作者：Peng, D. R.; Zhong, X. C.^*; Dong, X. T.; Huang, J. H.; Zhang, H.; Ma, L.; Wu, S. M.; Jiao, D. L.; Liu, Z. W.; Yu, H. Y.; Qiu, W. Q.; Ramanujan, R., V

来源：Journal of Alloys and Compounds, 2020, 823: 153726.

DOI：10.1016/j.jallcom.2020.153726

• Phase evolution
• Magnetocaloric effect
• LaFe11.6Si1.4/La70Co30 composites
• Co diffusion

LaFe11.6Si1.4/16 wt%La70Co30 composites were fabricated by hot-pressing (HP) followed by thermal diffusion treatment in the temperature range of 923-1273 K. Significant microstructural and phase evolution occurred during diffusion heat treatment. Thermal decomposition (TD) occurred between 1023 and 1223 K, which increased the Curie temperature (T-C) but smeared out the magnetic transition, decreasing magnetic entropy change (-Delta S-M). Co atoms first diffused into the alpha-Fe(Si) and LaFeSi (1:1:1) phases. And then, the alpha-Fe(Co,Si) and La(Fe,Co)Si phases, attached to large LaFe11.6Si1.4 particles, transformed to a NaZn13-type La(Fe,Co,Si)(13) (1:13) phase at 1273 K. Hence, a core-shell La(Fe,Co,Si)(13) phase formed, resulting in a table-like magnetic entropy change over a wide temperature range (similar to 202-292 K). Greater Co diffusion and more homogeneity of the composition of the 1:13 phase could be achieved by increasing the annealing time. The maximum magnetic entropy change (-Delta S-M)(max) of the composites at 0-2 T could be increased from 5.62 J/(kg.K) at similar to 196 K to 8.81 J/(kg.K) at similar to 244 K.

• 单位
  南阳理工学院; 北京科技大学; 桂林电子科技大学