Effect of spontaneous polarization on electron emission from PZT ferroelectric ceramics under high pulsed electric field

The paper describes measurements of electron emission current from PZT ferroelectric materials under external pulsed electric field. The investigations were carried out in a vacuum of 10^-1 Pa. Thyratron based high voltage pulse generator was used to obtain the high voltage pulses. The pulse applied to the ferroelectric cathode had the following parameters: peak voltage of up to 10 kV, rise time of 80 ns, time to half-decay of about 1 μs, and pulse repetition rate of up to 200 pps. PZT ceramic pellets were prepared so that the ratio of Zr/Ti was equal to 13/7. The pellets were poled under a dc electric field of up to 7 kV/cm at various temperatures and times, so that the different values of spontaneous polarization, P_s, were obtained. P_s was estimated on the basis of the E-P hysteresis measurements, which were carried out by means of the Sawyer-Tower bridge. The emitted peak current density was found to be up to 0.8 A/cm ², and the total emitted charge per pulse was up to 0.3 μC. It has been found that the charge emitted from PZT cathode under high voltage pulsed polarization reversal strongly depends on the P_s. Generally, the higher the polarization P_s (the higher the saturation of E-P hysteresis), the higher the charge emitted from PZT ferroelectric cathode