Influence of converse piezoelectric effects on the frequency properties of electron emission in PZT cathode

The influence of converse piezoelectric effect on the frequency of PZT cathode during the electron emission process was studied. The PZT cathodes were prepared by ordinary ceramic process and the diameter of PZT cathode is 25 mm as well as the thickness is 3 mm. The back electrode, whose diameter is 20 mm, and the grid electrodes, with intervals being 200 mum, were made of gold by using evaporation technology. The experimental setups include a high voltage pulse generator, vacuum chamber, oscilloscope and voltage divider. Several periodic peaks of emitted electron current were observed and the period is 180 ns. The prominent frequency of the waveforms is about 5.8 MHz, obtained from the frequency spectrum of the current waveforms. This value is close to the surface vibrating frequency of 6.6 MHz, calculated through the theories of surface acoustic waves in PZT ceramics. That the frequency of the emitted electron current was modulated by the surface vibration can be concluded from the above results based on the theories of surface acoustic waves, fast polarization switch and surface plasma induced ferroelectric emission. Thus the several periodic peeks observed from the emitted current can be well explained.