Giant pyroelectric energy harvesting and a negative electrocaloric effect in multilayered nanostructures

This work examines the potential of PbZr_0.53Ti_0.47O₃/CoFe₂O₄ (PZT/CFO) multi-layered nanostructures (MLNs) to achieve a giant electrocaloric effect (ECE) and enhanced pyroelectric energy harvesting. Unlike the conventional ECE, the effect of PZT/CFO MLNs is governed by dynamic magneto-electric coupling (MEC) and can be tuned by the arrangement of various ferroic layers. The ECE is investigated in the stacks of three (L3), five (L5) and nine (L9) alternating PZT and CFO layers. Intriguingly, all configurations exhibit a negative ECE, calculated using Maxwell relations, which has a high magnitude in comparison with the previously reported giant negative ECE (ΔT = 6.2 K). The maximum ECE temperature change calculated in three (L3), five (L5) and nine (L9) layers is 52.3 K, 32.4 K and 25.0 K respectively. In addition, the maximum pyroelectric energy harvesting calculated for these layers using a modified Olsen cycle is nearly four times higher than the highest reported pyroelectric energy density of 11=549 kJ m^-3 cycle^-1. This increase is attributed to the cumulative effect of multiple layers that induce an enhancement in the overall polarization, 1.5 times of lead zirconate titanate, and leads to abrupt polarization changes with temperature fluctuations. The present study also sheds light on material selection and the thermodynamic processes involved in the ECE and it is concluded that the refrigeration obtained from the reversed Olsen cycle is a combined effect of an isothermal entropy as well as the adiabatic temperature change.