Large barocaloric effects in thermoelectric superionic materials

J Min and AK Sagotra and C Cazorla, PHYSICAL REVIEW MATERIALS, 4, 015403 (2020).

DOI: 10.1103/PhysRevMaterials.4.015403

We predict the existence of large barocaloric effects above room temperature in the thermoelectric fast-ion conductor Cu2Se by using classical molecular dynamics simulations and first-principles computational methods. A hydrostatic pressure of 1 GPa induces large isothermal entropy changes of vertical bar Delta S vertical bar similar to 15-45 J kg(-1) K-1 and adiabatic temperature shifts of vertical bar Delta T vertical bar similar to 10 K in the temperature interval 400 <= T <= 700 K. Structural phase transitions are absent in the analyzed thermodynamic range. The causes of such large barocaloric effects are significant P-induced variations on the ionic conductivity of Cu2Se and the inherently high anharmonicity of the material. Uniaxial stresses of the same magnitude, either compressive or tensile, produce comparatively much smaller caloric effects, namely, vertical bar Delta S vertical bar similar to 1 J kg(-1) K-1 and vertical bar Delta T vertical bar similar to 0.1 K, due to practically null influence on the ionic diffusivity of the material. Our simulation work shows that thermoelectric compounds presenting high ionic disorder, like copper and silver-based chalcogenides, may render large mechanocaloric effects and thus are promising materials for engineering solid-state cooling applications that do not require the application of electric fields.

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