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 ΔSmaxP ~71 J K−1 kg−1 around room temperature, associated with a structural phase transition. The phase transition temperature, Tt, varies dramatically with pressure at a rate of dTt/dP ~0.79 K MPa−1, which leads to a very small saturation driving pressure of ΔP ~40 MPa, an extremely large barocaloric strength of ΔS/ΔP ~1.78 J K−1 kg−1 MPa−1, as well as a broad temperature span of ~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 Tt. This work is expected to advance the practical application of barocaloric refrigeration.

Qingyong Ren, Ji Qi, Dehong Yu, Zhe Zhang, Ruiqi Song, Wenli Song, Bao Yuan, Tianhao Wang, Weijun Ren, Zhidong Zhang, Xin Tong, Bing Li