Materials and device concepts for electrocaloric refrigeration

Electrocaloric (EC) materials provide a solid-state cooling technology without polluting liquid refrigerants and noisy mechanical parts. Currently, basic research in this field is mainly focused on materials with a first-order phase transition exhibiting a large polarization change in a narrow temperature region near the phase transition point (Curie temperature) and, thus, a large EC effect. In this contribution, device operation above Curie temperature will be discussed. In this case, the polarization change originates from the temperature coefficient of the dielectric permittivity. To optimize material properties for EC refrigerator applications, we adapt the modified Curie–Weiss law describing a large class of ferroelectrics with a diffuse phase transition. Device performance will be evaluated based on the expected cooling power in dependence on thermodynamic cycle time, total thermal resistance and EC material thickness. (paper)