Two modes of plasma-assisted electron emission from ferroelectric ceramics

It is shown that two quite different mechanisms may be responsible for surf ace plasma initiation at a polar surface of PLZT 7/65/35 ferroelectric cera mic. Priming electron emission required for surface flashover initiation ma y arise due to either field electron emission at triple junctions or electr on emission caused by polarization reversal. In the former case neither pol arization 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 ferroelectri c domains. This leads to a much higher emitted electron charge compared wit h 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.