A comprehensive model of ozone generation in dielectric barrier discharges is presented. The model combines the physical processes in the micro-discharges with the chemistry of ozone formation. It is based on an extensive reaction scheme including the major electronic and ionic processes. The importance of excited atomic and molecular states is demonstrated. Theoretical limits are given for the ozone production efficiency and the attainable ozone concentration. The most important parameters influencing the performance of ozonisers are identified. All theoretical predictions are compared to measured data.

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Dielectric-barrier discharges (silent discharges) are non-equilibrium discharges that can be conveniently operated over a wide temperature and pressure range. At about atmospheric pressure electrical breakdown occurs in many independent thin current filaments. These short-lived microdischarges have properties of transient high pressure glow discharges with electron energies ideally suited for exciting or dissociating background gas atoms and molecules. The traditional application for large-scale ozone generation is discussed together with novel applications in excimer UV lamps, high power CO, lasers and plasma display panels. Additional applications for surface treatment and pollution control are rapidly emerging technologies. Recent results on greenhouse gas recycling and utilisation in dielectric-barrier discharges are also discussed.

A review is presented of plasma chemical processes occurring in the volume part of electrical nonequilibrium discharges. The role of energetic electrons as initiators of chemical reactions in a cold background gas is discussed. Different discharge types (glow, corona, silent, RF, and microwave discharges) are investigated with respect to their suitability for plasma chemical processing. Emphasis is placed on the requirements of initiating and maintaining the discharge and, at the same time, optimizing plasma parameters for the desired chemical process. Using large-scale industrial ozone production as an example, the detailed process of discharge optimization is described. Other applications of volume plasma processing include other plasma chemical syntheses as well as decomposition processes such as flue gas treatment and hazardous waste disposal. If large gas volumes have to be handled, mainly the silent discharge and possibly also corona discharges have a chance of industrial acceptance as far as nonequilibrium plasma processing is concerned.

Dielectric-barrier discharges (silent discharges) combine the ease of atmospheric pressure operation with nonequilibrium plasma conditions suited for many plasma chemical processes. In most gases at this pressure the discharge consists of a large number of randomly distributed short-lived microdischarges. Their properties are discussed in detail. Traditionally mainly used for industrial ozone production, dielectric-barrier discharges have found additional large volume applications in surface treatment, high-power CO 2 lasers, excimer ultraviolet lamps, pollution control and, most recently, also in large-area¯at plasma display panels. Future applications may include their use in greenhouse gas control technologies. Historical aspects, properties and applications of dielectric-barrier discharges are discussed.