Abstract
The microscopic processes of fracture or breakdown are unknown, the models are contradicted or leave unexplained several observations, the suspected relationships between the electrical properties, the mechanical properties and the charge properties of the dielectrics are not confirmed by characterization of space charges and we do not know how to relate the results to the reliability of the materials. To overcome these difficulties: (1) we apply the energy localization principle used in mechanics and detonics, (2) we replace by electron traps that localize polarization energy, the defects imagined by Griffith in mechanics and dislocations used in detonation to explain the hot spot formation, (3) the effect of strain rates is taken into account because the localized energy is of the order of the binding energies and the trapping and detrapping characteristic times are of the order of the atomic polarization time (10-9 s). We can thus explain by multiphonon processes the transfer of the localized energy towards the bounds and explain the observations which occur when the strain rates are very high, (4) we develop an electron beam technique to measure the extension of the electron trapping domain and the localized energy beyond which a total discharge of the material occurs. These measurements characterize the space charges in the dielectric interfaces where the hot spots are formed. This technique makes it possible to reproduce most of the observations that remained unexplained and to link the measurements made to the properties and reliability of the insulators.
Highlights
The development of space charge measurement techniques, Ahmed and Srinivas (1997), Imburgia et al (2016), Vallayer et al (1999), was stimulated by the search for links between the formation of space charge and the electrical and mechanical behavior of insulators
We summarize recent developments in electron beam space charge characterization technique in a SEM and introduced about thirty years ago, Le Gressus et al (1991). They have resulted in a model of “Localized Energy Relaxation around defects” (LER) which is the basis of the experimental protocols implemented
We focus in particular on the instabilities detected by dynamic space charge characterization, Suzuoki et al (1998), Meng et al (2016), or by conduction current measurements, Mekni (2018), whose interest comes from what they could be damage precursor signals
Summary
The development of space charge measurement techniques, Ahmed and Srinivas (1997), Imburgia et al (2016), Vallayer et al (1999), was stimulated by the search for links between the formation of space charge and the electrical and mechanical behavior of insulators. We focus in particular on the instabilities detected by dynamic space charge characterization, Suzuoki et al (1998), Meng et al (2016), or by conduction current measurements, Mekni (2018), whose interest comes from what they could be damage precursor signals This model is summarized by four points: (1) the description of the electronic polarizability defects (EPD) that are electron traps, (2) the origin of the energy responsible for the damage, (3) the role of the strain and (4) of the strain rate These points make it possible to explain the link between space charge instabilities, the properties and the material reliability
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