Ultrasensitive barocaloric material for room-temperature solid-state refrigeration

One of the greatest obstacles to the real application of solid-state refrigeration is the huge driving fields. Here, we report a giant barocaloric effect in inorganic NH4I with reversible entropy changes of Delta S-P0 -> P(max) similar to 71 J K-1 kg -1 around room temperature, associated with a structural phase transition. The phase transition temperature, T-t, varies dramatically with pressure at a rate of dT(t)/dP similar to 0.79 K MPa-1, which leads to a very small saturation driving pressure of AP -40 MPa, an extremely large barocaloric strength of vertical bar Delta S-P0 -> P(max)/Delta P vertical bar similar to 1.78 J K-1 kg(-1) MPa-1, as well as a broad temperature span of similar to 41 K under 80 MPa. Comprehensive characterizations of the crystal structures and atomic dynamics by neutron scattering reveal that a strong reorientation-vibration coupling is responsible for the large pressure sensitivity of T-t. This work is expected to advance the practical application of barocaloric refrigeration.

Automated summary

A giant barocaloric effect has been observed in inorganic NH4I near room temperature, which could help overcome the driving field challenge in solid-state refrigeration. The material exhibits high reversible entropy changes and a structural phase transition. Analysis of the crystal structures and atomic dynamics reveals that a strong reorientation-vibration coupling is responsible for the pressure sensitivity. This research has the potential to advance the practical application of barocaloric refrigeration.