Direct Thermal Method to Characterize the Material Efficiency of Electrocaloric Lead Scandium Tantalate Multilayer Ceramic Capacitors

In this study, we characterize electrocaloric lead scandium tantalate (PST) samples by means of the adiabatic temperature change ΔTad and the dissipative heat qdiss with a direct thermal method. The figure of merit (FOM), defined as the ratio between the adiabatic temperature change and the thermal hysteresis, quantifies the losses of the material. Additionally, it is also possible to draw conclusions on the efficiency of a caloric cooling system based on the regenerator or cascaded approach. The maximum adiabatic temperature change of the measured samples results in ΔTad,max=(1.39±0.02) K and the dissipative heat yields qdiss=(0.39±0.05) J/(kg K), resulting in an FOM=(5.1±0.2). The efficiency for an ideal cascaded system is given by ηcas=0.56, and for the ideal regenerator, the efficiency is given by ηreg=0.84. The results demonstrate that the PST material in this study exceeds the maximum FOM in the literature by 34%.