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

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 Δ V / V 0 upon the martensitic transformation. Using the Ni 50 Mn 50 binary alloy as the prototype, a large transformation entropy change Δ S tr can be tailored in the vicinity of room temperature by simultaneously doping Cu and Ga. Especially, the |Δ S tr | values in the ⟨001⟩ A -textured Ni 30 Cu 20 Mn 39.5 Ga 10.5 and Ni 30 Cu 20 Mn 39 Ga 11 alloys prepared by directional solidification can be as large as 47.5 and 46.7 Jkg –1 K –1, respectively, due to the significant Δ V / V 0 values, i.e., 1.81 and 1.82%, respectively. Such enhanced Δ S tr values thus yield giant Δ T 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 (|Δ T ad /Δ σ 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.