Relationships between microstructure, mechanical and dielectric properties of different alumina materials

Thickness-dependence of the breakdown strength: Analysis of the dielectric and mechanical failure

“…As expected from literatures [2,[13][14][15] the breakdown strength decreases with increasing porosity. But in contrast to Liebault et al [2], who reported that a porosity of the sample below 5 vol-% has no effect on the breakdown strength, here, an effect of the porosity on the breakdown strength even below 5 vol-% can be shown.…”

“…The breakdown strength, E b , defined as breakdown voltage, V b , per sample thickness, t, is reported to be dependent on the microstructure [2][3][4], sample thickness [5][6][7][8][9] and loading condition [8,[10][11][12]. The influence of the porosity [2,[13][14][15], grain size [2-4, 13, 15-17], purity and secondary phase [2-4, 6, 7] on the breakdown strength have been investigated. However, no suitable holistic model has been developed, explaining the experimental results.…”

Dielectric breakdown of alumina single crystals

“…Defects of the microstructure such as pores, grain boundaries, impurities, crystallographic defects and secondary phases are considered as trapping sites. Therefore, it is generally believed that the resistance against dielectric breakdown is directly connected to microstructure properties 7,8,9,10 . In the present study, the focus is on the dielectric breakdown behaviour of alumina single crystals.…”

Effects of the Microstructure Induced by Sintering on the Dielectric Properties of Alumina

“…The dielectric properties of undoped corundum, α-alumina, of different kinds (single crystal or polycrystalline obtained by solid state sintering) have been the subject of numerous studies concerning, in particular, the breakdown strength and the charging behavior (Haddour et al, 2009;Liebault et al, 2001;Si Ahmed et al, 2005;Suharyanto et al, 2006;Thome et al, 2004;Touzin et al, 2010;Zarbout et al, 2008Zarbout et al, , 2010. The common feature pointed out by most of these investigations is the conspicuous role played by the microstructure and the impurities.…”

“…This parameter is intimately linked to the charging properties as breakdown originates from the enhancement of the density of trapped charges, which stems from the competition between charge trapping and conduction Le Gressus et al, 1991;Liebault et al, 2001;Haddour et al, 2009). The charges can be either generated by irradiation or injected through interfaces via an applied voltage.…”