Current from a Shock-Loaded Short-Circuited Ferroelectric Ceramic Disk

Thin circular disks of polarized ferroelectric ceramics were equipped with electrodes on their faces, and the electrodes were connected by a short circuit. Each disk was traversed by a stress wave, and the resulting current pulse through the short circuit was measured. The stress wave was generated by impact and made to propagate along the disk axis in a direction opposite to that of polarization. Current-pulse data are presented from tests with PZT 95/5, both normally sintered and hot-pressed, and with PSZT 68/7 for impact stresses ranging from a few to several tens of kilobars. Over this range of stress both the shape of the current pulse and its time integral are found to be strongly stress dependent. It is concluded that this behavior results from the combined effects of stress on (1) remanent polarization, (2) polarizability, and (3) conductivity of the ferroelectric material enveloped by the wave. In a narrow range of stress where remanent polarization is reduced to near zero and where conductivity is negligible, the observed behavior can be adequately described by means of a mathematical model which is developed. The model includes the effect of stress wavefront tilt which occurs in impact experiments to an extent that influences significantly the character of the current pulse. Some conclusions are drawn about permittivity of shock-loaded ferroelectrics and the extent to which remanent polarization is affected by the rapidly applied large electric fields which accompany the process of current production.