Study On Depolarization And Electrical-Response Of Porous PZT95/5Ferroelectric Ceramics Under Shock Loading

A ferroelectric is a material with spontaneous electrical polarization that can be reoriented by applying an external electric field. Under a dynamic shock wave compression, the poled ferroelectric ceramics can transform from ferroelectric (FE) to antiferroelectric (AFE) and release bound charges as the shock stress passes through it, which results in hundreds of kilowatts electrical power exporting in the external circuit. A PZT95/5ferroelectric ceramic, as the solid solution containing95mol.%PbZrO3and5mol.%PbTiO3, has been shown excellent performance under shock wave loads and is widely used as a source of pulsed power.In recent years, some of the test observations show that the porous PZT95/5ferroelectric ceramics under impact stress have better mechanical and electrical performance. Most of the existing theoretical research paid attention to the dense PZT95/5ferroelectric ceramics, and there were few theory researches on the mechanic and electrical response on porous ferroelectric ceramic by shock wave. This thesis studies the electrical-response and the related properties of poled porous PZT95/5ceramics under resistive loads in normal mode with the shock propagation perpendicular to the poling axis. The contents of this paper are as following:1. Based on the existing theoretical study, a model was built to describe the depolarization and electrical-response of porous PZT95/5ferroelectric ceramics under shock wave compression in the normal mode. In this model, the depoling process of porous PZT95/5ferroelectric ceramics was analyzed by a parallel circuit with a current source, a capacitance and a conductance, and the circuit load. The model introduced relaxation characteristic time to describe the relaxation process of the polarization of shocked ceramic changes. In addition, the effects of porosity on the dielectric constant and the differences of the dielectric constant and conductivity in the region ahead of and behind the shock front were taken into account in the modeling. Based on the parameters of the previous experimental, the calculated depoling current of porous PZT95/5was obtained by numerical analysis and compared with the experimental results. The result showed that the computation results are in good agreement with the experiments.2. Considered the mechanical response of the porous material under high shock wave pressure, the relation between the shock wave velocity and the porosity of the ferroelectric ceramics under shock wave compression was obtained. Based on the developed relaxation model of the porous ferroelectric ceramics under shock wave load, the effects of porosity on the wave velocity and the remanent polarization were taken into account. The output current characteristics of the porous PZT95/5ferroelectric ceramics under shock wave compression in the normal mode were obtained through analysis and simulation, and effects of permittivity and conductivity changes on the depoling current was also analyzed. The results showed this model works well.3. Based on the model built in this study that describes the depolarization and electrical-response of porous PZT95/5ferroelectric ceramics under shock wave compression in the normal mode, the resistivity in the area behind the shock front of the corresponding dense and the porous PZT95/5ferroelectric ceramics was analyzed.