Effect of Piezoelectric Resonance in a Ferroelectric Plasma Source

Ferroelectric plasma sources have been studied extensively for the past few decades. Potential applications include cathodes for traveling wave tubes or high-energy electron beams, triggers for pulsed power gas switches, and microspacecraft propulsion. In addition to liberation of ions and electrons from the ferroelectric itself, one hypothesized source of particles is from plasma generated on the ferroelectric surface. Factors identified influencing the plasma formation include triple point enhancement due to microgaps and surface charges generated by polarization switching. In this paper, we detail the utilization of piezoelectric resonance to generate plasma with reduced applied voltages. To study this effect, an rf bipolar voltage is applied across the ferroelectric. A non-linear device impedance is observed around the radial resonant frequency of the disk. The plasma breakdown voltage is shown to correlate with the impedance of the device. This effect is similar to what occurs in Rosen-type piezoelectric transformers manufactured with the secondary in a dielectric barrier discharge geometry. In our experiments, the plasma is generated in backgrounds of both vacuum and atmospheric pressure air. In addition, both lead zirconate titanate and lithium niobate ferroelectrics are utilized.