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

Abstract

LaFe 11.6 Si 1.4 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 LaFe 11.6 Si 1.4 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 (DS M ) for the arc-melted LaFe 11.6 Si 1.4 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 LaFe 11.6 Si 1.4 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 LaFe 11.6 Si 1.4 compound was observed. The DS M , obtained for a field change of 5 -0T (decreasing field), for the SPS LaFe 11.6 Si 1.4 compound decreases to 7.4 J kg -1 K -1 . The T C 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 LaFe 11.6 Si 1.4 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 LaFe 11.6 Si 1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe 11.6 Si 1.4 compounds in low-field magnetic refrigeration applications.

Energy Applications of Magnetocaloric Materials

“…The authors reported a thermal conductivity of 6 W mK –1 and reproducible Δ T ad of 5.4 K for a magnetic field change of 1.93 T. They also applied a method for processing magnetocaloric regenerators via metallic additive manufacturing. The method was implemented by Shamba et al, who processed LaFe 11.6 Si 1.4 alloys using spark plasma sintering. A comprehensive experimental study on the use of Gd was performed by Trevizoli et al In the first part of the study, the authors fabricated stainless‐steel regenerator samples with different geometries: parallel plate, pin array, and sphere‐packed bed.…”

Investigation into the magnetic properties of CoFeNiCr y Cu x alloys

“…For the traditional magneto-caloric materials, such as LaFe 11.6 Si 1.4 and MnAs, the Curie temperature also has to be tuned using dopants such as Co, H and Si, which moves the T c to around 280-300 K, but this decreases the refrigerant capacity. At 2 T, the refrigerant capacity of LaFe 11.6 Si 1.4 is in the range 100-150 J K −1 [11,29,33] for a temperature range between 180 K and 220 K and for MnFeP 1−x As x is in the range 200-250 J K −1 [11,34] for a temperature range 260-340 K. Thus they are higher than those measured for the HEAs, but have the disadvantages mentioned above, meaning the search for new materials is still ongoing, and HEAs may hold the key in the long run.…”