Electrical degradation and breakdown of mica

In conclusion, combining the information presented by both experimental programmes, the following points emerge. Given that the results of the discharge investigation can be related to an “intrinsic” mechanism of breakdown, the discharge must produce a highly localised (≈ 10 µm radius) stress site at the mica surface. Moreover, this stress site would require to be sufficiently small to essentially remove the effect of precipitate ionisation in amber phlogopite from the breakdown mechanism. Although the results obtained for amber phlogopite with the 25 [m electrode suggest that some effect, which can be related to the mica structure, is occurring, it is difficult to believe, for the sample thicknesses investigated, that discharge conditions would produce such a consistent breakdown strength if related to the above mechanism.