Colossal Barocaloric Materials

The discovery of colossal barocaloric effects (CBCEs) in plastic crystals has greatly advanced the prospects of solid-state cooling as a promising alternative to vapor-compression refrigeration. This review examines the physical origins of CBCEs, emphasizing the large entropy changes associated with multiple internal degrees of freedom, such as orientational, occupational, magnetic, dipolar, charge, and conformational disorders, as well as phonon renormalization in the absence of disorder. Key performance metrics, including transition temperature, pressure sensitivity, thermal hysteresis, thermal conductivity, and adiabatic temperature change, are analyzed with a focus on their intrinsic trade-offs. Looking ahead, advancing the fatigue resistance of barocaloric materials through microstructural design, such as encapsulation with solid lubricants, and developing real-time evaluation tools will be essential for long-term durability. Additionally, future efforts should prioritize the engineering of proof-of-concept barocaloric cooling devices, with emphasis on pressure-loading systems and efficient heat exchange to fully realize their practical potential.