High-performance spark plasma sintered HoNi2 and ErAl2 Laves phases for hydrogen magnetocaloric liquefaction

Abstract

Magnetocaloric hydrogen liquefaction is an energy-efficient alternative to conventional hydrogen liquefaction methods, enabling the broader adoption of hydrogen as a clean energy carrier. To realize this technology, it is essential to develop magnetocaloric materials that exhibit excellent performance in shapes compatible with magnetic refrigeration devices. In this work, we utilize the Spark Plasma Sintering (SPS) technique to fabricate highly dense (∼95 %) samples of the cryogenic magnetocaloric refrigerants HoNi2 and ErAl2, employing rapidly solidified single-phase melt-spun ribbons as precursors. XRD analyses show that the alloys present the cubic MgCu2-type crystal structure of the Laves phase (C15; space group ). The as-prepared SPS samples exhibit enhanced saturation magnetization values at 2 K while maintaining similar magnetic properties and the excellent magnetocaloric response of the ribbon precursors. The as-sintered bulk SPS samples exhibit superior magnetocaloric performance compared to the best data reported in the literature for bulk alloys: (a) for HoNi2 |ΔSM|max = 18.0 (28.8) Jkg−1K−1 and |ΔTad|max = 6.3 (11.0) K at 2 T (5 T), and; (b) for ErAl2 |ΔSM|max = 25.5 (38.1) Jkg−1K−1 and |ΔTad|max = 6.0 (11.0) K at 2(5) T. These results highlight that Spark Plasma Sintering is a viable consolidation technique for producing RXi2 Laves phase materials (with X = Al and Ni), exhibiting optimal magnetocaloric performance suitable for hydrogen magnetocaloric liquefaction technology.