Designing magnetocaloric materials for hydrogen liquefaction with light rare-earth Laves phases

Abstract

Magnetocaloric hydrogen liquefaction could be a “game-changer” for liquid hydrogen industry. Although heavy rare-earth based magnetocaloric materials show strong magnetocaloric effects in the temperature range required by hydrogen liquefaction (77 ~ 20 K), the high resource criticality of the heavy rare-earth elements is a major obstacle for upscaling this emerging liquefaction technology. In contrast, the higher abundances of the light rare-earth elements make their alloys highly appealing for magnetocaloric hydrogen liquefaction. Via a mean-field approach, it is demonstrated that tuning the Curie temperature (TC) of an idealized light rare-earth based magnetocaloric material towards lower cryogenic temperatures leads to larger maximum magnetic and adiabatic temperature changes (ΔST and ΔTad). Especially in the vicinity of the condensation point of hydrogen (20 K), ΔST and ΔTad of the optimized light rare-earth based material are predicted to show significantly large values. Following the mean-field approach and taking the chemical and physical similarities of the light rare-earth elements into consideration, a method of designing light rare-earth intermetallic compounds for hydrogen liquefaction is used: tunning TC of a rare-earth alloy to approach 20 K by mixing light rare-earth elements with different de Gennes factors. By mixing Nd and Pr in Laves phase (Nd,Pr)Al2, and Pr and Ce in Laves phase (Pr, Ce)Al2, a fully light rare-earth intermetallic series with large magnetocaloric effects covering the temperature range required by hydrogen liquefaction is developed, demonstrating a competitive maximum effect compared to the heavy rare-earth compound DyAl2.

Magnetocaloric materials for hydrogen liquefaction

“…89,90 This is because most of these compounds display FM to PM SOPTs between 13 and 80 K with a remarkable MCE. 91 In particular, those compounds with R = Dy, Ho and Er show an additional SR transition below the Curie temperature which enhances their MCE response, 92,93 reaching the outstanding mark of 36.2 J kg −1 K −1 and 11 K for and respectively for ErAl 2 . 92 Very recently, Liu et al 94 have explored the MCE of NdAl 2 and PrAl 2 together with some of their rare-earth solid solutions leading to remarkable figures.…”

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si)13-Based Compounds

“…17−19 However, the reliance of current magnetocaloric materials on highly resource critical, 20−22 heavy rare-earth elements, such as Er, Dy, and Ho, though important for fundamental research and device development, makes global commercial usage unsustainable. 23 In addition, monocaloric cooling requires the stacking of numerous different chemical compositions in order to provide sufficient cooling power over a large enough temperature range, and these chemical modifications often destabilize the desired magnetocaloric active phase, leading to impurities, reduced caloric effects, and an overall more complex material synthesis process.…”

“…Even though magnetocaloric cooling has been predominantly tailored for room temperature applications, one of its first utilizations realized ultralow temperatures below 1 K by adiabatic demagnetization of paramagnetic salts. , Very recent results on Laves phases and HoB 2 are a manifestation of currently re-emerging interest in caloric cooling at cryogenic temperatures, at the present time in the framework of gas liquefaction, which allows the utilization of superconducting magnets and thereby large external magnetic fields driving the phase transitions. − However, the reliance of current magnetocaloric materials on highly resource critical, − heavy rare-earth elements, such as Er, Dy, and Ho, though important for fundamental research and device development, makes global commercial usage unsustainable . In addition, monocaloric cooling requires the stacking of numerous different chemical compositions in order to provide sufficient cooling power over a large enough temperature range, and these chemical modifications often destabilize the desired magnetocaloric active phase, leading to impurities, reduced caloric effects, and an overall more complex material synthesis process.…”