Microstructural origin of the dielectric breakdown strength in alumina: A study by positron lifetime spectroscopy

Alumina based ceramics for high-voltage insulation

“…Then it is reasonable to assume that the ability of a material to resist high-voltage conditions without reaching breakdown is directly linked to its charge trapping and scattering properties. 2,3 Of course, these properties depend on the material microstructure 4,5 and in particular on the interfaces. Indeed, grain boundaries, i.e.…”

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

“…It is worth noting that, at room temperature and in the same impure polycrystalline samples, breakdown strength increases with the grain sizes (Liebault, 1999;Si Ahmed et al, 2005), which is also the case for the fraction of removed charges R. Therefore this correlation confirms the importance of charge spreading to prevent breakdown.…”

“…In this section, complementary investigations concerning the use of Positron Annihilation Lifetime Spectroscopy "PALS" for the characterization of defects in alumina will be summarized Si Ahmed et al, 2005). After a short description of the procedure, we will spotlight the results relevant to the charging properties.…”

“…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.…”

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.…”