Two modes of plasma-assisted electron emission from ferroelectric ceramics

It is shown that two quite different mechanisms may be responsible for surface plasma initiation at a polar surface of PLZT 7/65/35 ferroelectric ceramic. Priming electron emission required for surface flashover initiation may arise due to either field electron emission at triple junctions or electron emission caused by polarization reversal. In the former case neither polarization reversal nor ferroelectric state is required. In the latter case the surface plasma can be generated twice during the applied voltage pulse due to both forward polarization reversal and backswitching of ferroelectric domains. This leads to a much higher emitted electron charge compared with that caused by the polarization reversal. The experimental data enable us to conclude that, regardless of the initiation mechanism, strong electron emission from ferroelectric cathodes is a plasma-assisted effect.