The promising room-temperature magnetic refrigeration materials - Misch-metal (MM)(2)Fe17-xSix (x=0-1.5) compounds

摘要

The phase structure, magnetic properties, magnetocaloric effect (MCE) and relative cooling power (RCP) of MM2Fe17-xSix (x = 0-1.5) compounds were studied. The phase transition temperature was increased from 238 K to 366 K with the increase of Si content. The X-ray diffraction (XRD) patterns indicate that the MM2Fe17-xSix (x = 0-1.5) compounds crystallize primarily in a rhombohedral phase with Th2Zn17 type crystal structure coexisting with a small amount of the precipitation alpha-Fe phase. These results are reinforced by backscattered scanning electron microscope (SEM) images and electron energy dispersive X-ray spectroscopy (EDX) analysis. The maximum values of magnetic entropy change (Delta S-M) for MM2Fe17-xSix (x = 0, 0.3, 0.6, 1.0) compounds are -2.1 J kg(-1)K(-1), 1.3 J kg(-1)K(-1), 1.5 J kg(-1)K(-1), 1.8 J kg(-1)K(-1) for field change of 0-2 T and -4.0 J kg(-1)K(-1), 2.7 kg(-1)K(-1), 3.1 kg(-1)K(-1), 3.5 kg(-1)K(-1) for field change of 0-5 T. The estimated RCP values are larger than 100 J kg(-1) and 350 J kg(-1) for the field change of 0-2 T and 0-5 T, respectively. The working temperature range delta T-FWHM is larger than 50 K and 100 K with the field changes of 0-2 T and 0-5 T, respectively. The temperature range and RCP values are comparable to the second-order phase transition (SOFT) materials R2Fe17 (R = Pr, Nd) and Gd, but the cost of MM2Fe17-xSix is only about 25% and 10% compared with R2Fe17 (R = Pr, Nd) and Gd, respectively. (C) 2020 Elsevier B.V. All rights reserved.