Discharge plasmas generated by piezoelectric transformers and their applications

The characteristics of discharge plasma generated by piezoelectric transformers (PTs) and the practical applications of PT-based plasma reactors are reviewed in this paper. PTs of Pb(Zr center dot Ti)O-3 generate high voltage by the piezoelectric effect, which can cause excitation and ionization of atoms and molecules, resulting in the generation of discharge plasma. When a narrow gap exists between the PT surface and a dielectric layer having a metal back electrode, dielectric barrier discharge (DBD) occurs at atmospheric pressure and above. The mechanical vibration of the PT and the resultant surface potential, which relate to electro-mechanical energy conversion by the piezoelectric effect, are investigated using a laser Doppler vibrometer and probe method, respectively. The characteristics of DBD are examined based on light patterns detected by the intensified charge coupled device camera, and the fundamental parameters of the filamentary discharge are determined. PT-generated DBD is shown to be applicable for ozone generation and as excimer lamps, and high-power operation is demonstrated using a parallel-driven hexad plasma reactor.