Electron emission for ferroelectric ceramics

The authors report the results of experiments on the emission of electrons from ferroelectrics. A sample of PZT is pulsed to reverse the direction of the spontaneous polarization within the material. This releases of the surface charge accumulated on the ferroelectric which is needed to reduce the external electric field to a low value. Surface charge densities may amount to about 0.5 C/m2. In these experiments the emitted electron current density reaches a peak value of up to 70 A/cm2 for a diode gap of 4 mm and an extraction voltage of 500 V. Beam current densities exceed the Child Langmuir law for space charge limited emission by factors of up to 400. They present measurements showing the dependence of the emission on the diode voltage and spacing. A discussion is presented summarizing their present understanding of the emission process and its limitations