Giant barocaloric effects at low pressure in ferrielectric ammonium sulphate

TLDR

Caloric effects are intensively studied for environmentally friendly cooling, but magnetocaloric and electrocaloric approaches require large magnetic or electric fields that are difficult to generate economically or apply without breakdown. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. By applying hydrostatic pressure variations close to the ferrielectric transition, the authors induce large barocaloric responses. The measured barocaloric effects exceed those previously observed near magnetostructural transitions in magnetic materials, indicating that many unexplored ferroelectric compounds could host similarly large barocaloric responses and enable barocaloric cooling devices.

Abstract

Abstract Caloric effects are currently under intense study due to the prospect of environment-friendly cooling applications. Most of the research is centred on large magnetocaloric effects and large electrocaloric effects, but the former require large magnetic fields that are challenging to generate economically and the latter require large electric fields that can only be applied without breakdown in thin samples. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. We find barocaloric effects and strengths that exceed those previously observed near magnetostructural phase transitions in magnetic materials. Our findings should therefore inspire the discovery of giant barocaloric effects in a wide range of unexplored ferroelectric materials, ultimately leading to barocaloric cooling devices.