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Item type:Publication, Access status: with files , Thickness-dependence of the breakdown strength: analysis of the dielectric and mechanical failureThe breakdown strength as well as the mechanical strength of ceramic materials decreases with increasing volume. The volume-effect of the mechanical strength can be explained by the Weibull theory. For the breakdown strength the same explanation has been often assumed. In order to validate this assumption breakdown strength and mechanical strength of alumina samples with defined porosities were compared. Differences in the Weibull moduli of breakdown and mechanical strength distributions indicate that the volume-effect cannot explain the thickness-dependence of the breakdown strength. In particular, the thickness-dependence of the breakdown strength always leads to a Weibull modulus of two which is not in agreement with the measured Weibull moduli for samples with constant thickness. It can be concluded that the thickness-dependence of the breakdown strength cannot be explained by the Weibull concept. A recently developed breakdown model which is based on space charge injection is able to explain the experimental results.Publicationtype: Journal ArticleScopus© Citations 85 645 3576 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Dielectric breakdown of alumina single crystalsThe bulk breakdown behaviour of alumina single crystals with two different crystal orientations, {11-20}-plane (single crystal A) and {0001}-plane (single crystal C), have been studied. Therefor plan-parallel single crystal samples were electrically loaded until dielectric breakdown was achieved. For each crystal orientation, a characteristic breakdown channel direction through the sample could be defined. In C-oriented crystals the breakdown channel originated parallel to the c-axis. For A-oriented crystals however, the breakdown channel crossed the sample in an oblique direction; the angle between crystal surface and breakdown channel was 60°. Here, the breakdown channel crossed the sample along an A-plane. Although the breakdown channel paths of A and C crystals are different, the observed breakdown strength are identical within the scatter range.Publicationtype: Working Paper822 1644