Secondary ionization coefficientγof MgO, SrO and CaO and the correlation betweenγand charge accumulated on CaO in argon

Abstract

An experimental investigation of Townsend's secondary ionization coefficient γ is carried out for MgO, SrO and CaO film electrodes. These oxides are utilized, or are to be utilized, in next-generation plasma display panels. All of the experiments are performed in argon. In particular, in the case of CaO film, our attention is attracted to the effect of charge accumulated on CaO film. For this purpose, the breakdown voltage V s is observed from waveforms of the gap voltage and charge accumulated on the dielectric film electrodes with the repeated breakdown. Townsend's criterion is utilized to estimate γ from the breakdown voltage. In the case of the CaO film, γ increases gradually with repeated breakdowns and reaches a stationary value. The increase of γ is considered to be due to the charge that accumulates on the dielectric electrode triggering the next breakdown. Therefore, it is concluded that the increased γ is sustained by a combined process consisting of restarted electrons that have accumulated on the CaO film and the original γ action, as observed in metallic electrodes in a low-pressure gas discharge.

Gradual increase in secondary ionization coefficientγand charge accumulation on a dielectric electrode during DBD with repeated breakdown

“…Thus, we discuss the effect of the surface roughness on DBD characteristics to distinguish the effects of the local electric field distribution and the charge accumulation on the alumina electrode. On the basis of our results, we conclude that these accumulated electrons induce the formation of an atmospheric-pressure Townsend discharge (APTD) [9,14,24].…”

“…We previously reported the secondary ionization coefficients for MgO, SrO and CaO film electrodes and the charge accumulated on them [9,23,24]. The results of the experiments suggested a positive correlation between the secondary ionization coefficient and the charge accumulated on a CaO film.…”

“…Figure 8 shows the secondary ionization coefficient γ of the alumina evaluated using Townsend's criterion [9,23,24] determined from (a) the value of V s at the first breakdown and (b) the stationary value in figure 7. Townsend's criterion is described as…”

“…Therefore, it is necessary to know which materials are suitable for DBD electrodes. From the results of our previous investigation [9], we consider that the electrode material is an important factor determining DBD characteristics. For example, Golubovskii et al [10] investigated the effect of the barrier material in a Townsend barrier discharge and argued the importance of the dielectric permittivity of the barrier material.…”