Cathodo- and electro-luminescence spectra in insulating polymers: A parallel approach for inferring electrical ageing mechanisms

Abstract

Films of poly(ethylene naphthalate), polyethylene (either low density or cross-linked) and epoxy resins have been irradiated with electrons having kinetic energies of up to 10 keV, i.e. able to break bonds of the polymeric chains (featuring therefore hot electrons effects). The so-called cathodoluminescence spectrum has been acquired for different electron energies. With the various materials tested, we were able to reproduce the EL spectrum of these materials. These results allow to associate electroluminescence and electrical ageing in an implicit scheme, opening the way for defining safety limits in terms of electric stresses applied to a material for a given application.

Advanced Characterization Techniques Based on Luminescence in XLPE and Modified XLPE

“…Luminescence is the light emitted by a substance when the excitation is not due to heat, by opposition to incandescence. The excited states responsible for material luminescence can be produce by different excitation sources [6], among them: photon absorption (photoluminescence PL) [7], chemical reactions (chemiluminescence CHL) [8], recombining charges (recombination induced luminescence RIL) [9] [10], electric field application (electroluminescence EL) [11] [12], electron beam irradiation (cathodoluminescence CL or electron-beam induced luminescence EBIL) [13] [14] [15], temperature (thermoluminescence TL) [16] [17] [18], etc. PL, CHL, RIL, EL, EBIL, TL refer to the source of excitation itself which can generate a series of elementary excitations contributing to the luminescence.…”

“…With the different ways the material was excited, PL, including PL of oxidized PE, PIL, and chemiluminescence during thermal oxidation, never such emission was revealed. Only with e-beam excitation was it reproduced [15] [77] [78]. It led us to consider electron beam as a prototype source for understanding the EL mechanisms with a much more yied than can be provided under electric field.…”

Variations in Cathodoluminescent Intensity of Spacecraft Materials Exposed to Energetic Electron Bombardment

“…Figure 4 shows three cathodoluminescence spectra typical of spacecraft materials which are all similar in the visible region, and exhibit multiple peaks indicative of multiple types of defects. The cynate ester [12] and SiO 2 [3] spectra were acquired at USU; the epoxy spectra is from a different facility [6].…”

“…Cathodoluminescent spectra of three highly disordered insulating materials. Materials shown are: cynate ester/graphite fiber composite (red solid curve) at ~100 K [12], epoxy resin at ~295 K (blue dashed curve) [6], and SiO2-coated mirror at ~269 K (green dash-dotted curve) [3]. The spectra are normalized at maximum intensities and are not corrected for the wavelength-dependant relative detector sensitivity.…”

“…Determinations of the absolute and relative cathodoluminescent intensity of spacecraft materials per incident electron flux are essential to predict and mitigate consequences for optical detection [2] and for stray light contamination in space-based observatories [1,3]. They also Research provide important information about the defect structure and electron transport properties of these materials [4][5][6][7][8].…”