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|Title:||Electroluminescence excitation mechanisms in an epoxy resin under divergent and uniform field.|
Dissado, Len A.
Fothergill, John C.
|Publisher:||Institute of Electrical and Electronics Engineers (IEEE)|
|Citation:||IEEE Transactions on Dielectrics and Electrical Insulation, 2002, 9 (1), pp. 150-160.|
|Abstract:||Electroluminescence excitation mechanisms have been investigated in epoxy resin under divergent and uniform field situations. Metallic wires embedded in the resin were used to produce field divergence whereas film samples were metallised to obtain a uniform field. Electroluminescence under divergent field was stimulated by an impulse voltage. Light was emitted on the positive and negative fronts of the square pulses when the field exceeded 20 kV/mm at the wire surface, with equal intensity and without polarity dependence. There was evidence of space charge accumulation around the wires in multiple-pulse experiments. Charge injection and extraction occurring at both fronts of the pulse provide the condition for EL excitation. Further excitation of the EL during the plateau of the voltage pulse is prevented by the opposite field of the trapped charge. Field computation with and without space charge supports the proposed interpretation. A DC voltage was used for the uniform field experiments. A continuous level of electroluminescence is found at 175 kV/mm. Charging/discharging current measurements and space charge profile analyses using the pulsed electro-acoustic (PEA) technique were performed at different fields up to the EL level. Dipolar orientation generates a long lasting transient current that prevents the conduction level being reached within the experimental protocol (one hour poling time). The continuous EL emission is nevertheless associated with a regime where the conduction becomes dominant over the orientational polarization. Polarization and space charge contribute to the PEA charge profiles. Homo-charge injection at anode and cathode is seen at 20 kV/mm and a penetration of positive space charge in the bulk is detected above 100 kV/mm, suggesting an excitation of the continuous EL by bipolar charge recombination.|
|Rights:||This is the author's final draft of the paper published as IEEE Transactions on Dielectrics and Electrical Insulation, 2002, 9 (1), pp. 150-160. Copyright © 2002 IEEE. The final version is available from http://ieeexplore.ieee.org/. Doi: 10.1109/94.983899. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Leicester’s products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to firstname.lastname@example.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.|
|Appears in Collections:||Published Articles, Dept. of Engineering|
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