Fundamental Limits To The Transfer Of Energy Harvested From Ferroelectric Materials Under Shock Loading

Ferroelectrics are capable of producing megawatt power levels under shock loading due to stress-induced phase transformations, resulting in depolarization of the ferroelectric materials. This power can be used for generation of high voltages, high currents, or ultrahigh-power electromagnetic radiation. The results are reported herein on an experimental study of limitations on energy harvested from shocked Pb-0.99(Zr0.95Ti0.05)(0.98)Nb0.02O3 and PbZr0.52Ti0.48O3 ferroelectrics and transferred to external electrical systems. The experimental results indicate that one of the limits to the energy transfer is electric breakdown that occurs within ferroelectric specimens during shock wave transit and depolarization, interrupting the energy transfer process and resulting in energy losses. It was revealed that the mechanism for breakdown in shocked ferroelectrics differs depending on the energy transfer time range, making a significant impact on the energy transfer process. High-speed photography and analysis of outputs for the two ferroelectrics indicate that for energy transfer times exceeding eight microseconds, the mechanical fragmentation of the ferroelectric material caused by the shock and resulting release waves following the shock wave front plays an important part in the breakdown process, while a thermal runaway dominates the breakdown at shorter energy transfer times. The heretofore disregarded mechanism of electric breakdown of the mechanically fragmented dielectric media is an unavoidable time-limiting factor for energy transfer from ferroelectrics under shock loading. The results obtained in this study are important for understanding the behavior of ferroelectrics during shock wave transit under high electric fields and for ultrahigh-power applications of ferroelectric materials.