Giant Elastocaloric Effect in Ni-Mn-Ga-Based Alloys Boosted by a Large Lattice Volume Change upon the Martensitic...

High-performance elastocaloric materials are highly sought in developing energy-efficient and environmentally friendly solid-state elastocaloric refrigeration. Here, we present an effective strategy to achieve a giant elastocaloric response by enlarging the lattice volume change ΔV/V₀ upon the martensitic transformation. Using the Ni₅₀Mn₅₀ binary alloy as the prototype, a large transformation entropy change ΔS_tr can be tailored in the vicinity of room temperature by simultaneously doping Cu and Ga. Especially, the |ΔS_tr| values in the ⟨001⟩_A-textured Ni₃₀Cu₂₀Mn_39.5Ga_10.5 and Ni₃₀Cu₂₀Mn₃₉Ga₁₁ alloys prepared by directional solidification can be as large as 47.5 and 46.7 Jkg^-1 K^-1, respectively, due to the significant ΔV/V₀ values, i.e., 1.81 and 1.82%, respectively. Such enhanced ΔS_tr values thus yield giant ΔT_ad values of up to -23.5 and -19.3 K on removing the compressive stress in these two alloys, being much higher than those in Heusler-type alloys reported previously. Moreover, owing to the relatively low driving stress endowed by the highly textured microstructure, the specific adiabatic temperature change (|ΔT_ad/Δσ_max|) in the present work can be as large as 77.2 K/GPa. This work is expected to provide new routes in designing high-performance elastocaloric materials with the combination of a giant elastocaloric response and low driving stress.