Assessing rapid solidification processing to produce magnetocaloric RFeSi alloys (R= Tb, Dy) for natural gas liquefaction

Abstract

This work addressed the synthesis of melt-spun ribbons of the ternary intermetallic ferromagnetic phases RFeSi with R = Tb and Dy, presenting a thorough characterization of their structural, magnetic, and magnetocaloric behavior. Both compounds have been referred to as suitable magnetic refrigerants in the natural gas liquefaction temperature range. The primary phase in ribbon samples of both compounds shows the CeFeSi-type tetragonal crystal structure (space group P4/nmm), with Curie temperatures of 124 K and 89 K for TbFeSi and DyFeSi, respectively. Notably, a sizeable increase in the coercive field appeared below 20 K. However, for a magnetic field change of 2 T, the maximum values of the magnetic entropy change (|ΔSM|max) were 3.4 J kg−1 K−1 and 3.8 J kg−1 K−1 for TbFeSi and DyFeSi ribbon samples, respectively, reflecting a reduction of approximately 60% compared to reported findings for bulk alloys. In contrast, the refrigerant capacity under a magnetic field change of 2 T measured 120 J kg−1 for TbFeSi and 109 J kg−1 for DyFeSi. The reduction in |ΔSM|max is mainly due to a broader magnetic transition compared to the previous results for bulk alloys. Based on the RFeSi ribbons obtained, a biphasic magnetocaloric composite with a broad table-like magnetic entropy change curve, as that required for an Ericsson-type refrigeration cycle, is designed.