Multicaloric materials show reversible thermal changes under the application of hydrostatic pressure, uniaxial stress, electric field or magnetic field. These materials operate near first-order phase transitions, where lattice parameters and mechanical properties show field-driven changes that are sharp . These changes are particularly large in some electrocaloric materials driven by electric field, where changes in volume up to 4%  can lead to the formation of cracks that can hinder the application of these materials in cooling devices.
Ammonium sulphate is one of the most promising multicaloric materials, exhibiting giant electrocaloric effects and pressure-driven barocaloric effects near its ferrielectric phase transition [3,4]. Here, we show that the change in volume associated with the transition creates cracks, and that these cracks influence the multicaloric response of our material. We use resonant ultrasound spectroscopy (RUS) and acoustic emission (AE) to investigate microstructural evolution and crack formation.
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