Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4

Abstract

LaFe11.6Si1.4 alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe11.6Si1.4 alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (ΔSM) for the arc-melted LaFe11.6Si1.4 compound, obtained for a field change of 5 − 0T (decreasing field), was estimated to be 19.6 J kg−1 K−1. The effective RCP at 5T of the arc-melted LaFe11.6Si1.4 compound was determined to be 360 J kg−1 which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe11.6Si1.4 compound was observed. The ΔSM, obtained for a field change of 5 − 0T (decreasing field), for the SPS LaFe11.6Si1.4 compound decreases to 7.4 J kg−1 K−1. The TC also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe11.6Si1.4 compound spreads over a larger temperature range with the RCP value at 5T reaching 288 J kg−1 corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe11.6Si1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe11.6Si1.4 compounds in low-field magnetic refrigeration applications.