Interfacial charge dynamics of cross-linked polyethylene/ethylene-propylene-diene dual dielectric polymer as revealed by energy band structure

The discontinuous charge relaxation time related to the electrical conductivity and permittivity, i.e., traditional Maxwell-Wagner relaxation, is the prevailing explanation for the interfacial charge behavior in multi-layered dielectrics. However, the unipolar/bipolar charge dynamics and the corresp...

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Bibliographic Details
Published in:IEEE transactions on dielectrics and electrical insulation 2019-12, Vol.26 (6), p.1755-1762
Main Authors: Wang, Weiwang, Li, Shengtao, Tanaka, Yasuhiro, Takada, Tatsuo
Format: Article
Language:English
Subjects:
Band structure of solids
Charge injection
Charge measurement
Charge transfer
Charge transport
Conductivity
Cross-linked polyethylene
Dielectric measurement
Dielectric relaxation
Dielectrics
Electric fields
Electrical resistivity
energy band structure
energy level
Energy levels
interface
Multilayers
Polyethylene
Propylene
Relaxation time
Space charge
Trapping
trapping site
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Summary:The discontinuous charge relaxation time related to the electrical conductivity and permittivity, i.e., traditional Maxwell-Wagner relaxation, is the prevailing explanation for the interfacial charge behavior in multi-layered dielectrics. However, the unipolar/bipolar charge dynamics and the corresponding mechanisms from a microscopic viewpoint remain unclear. This work focuses on the dynamics of the interfacial charges in cross-linked polyethylene (XLPE)/ethylene-propylene-diene (EPDM) dual layers to reveal the interfacial charge mechanisms using the energy band structure. The interfacial charge accumulation behavior of the XLPE/EPDM dual-layered structures is clearly observed under electrical stress. Either unipolar or bipolar charges occur at the interface, accompanied by charge injection, and trapping then occurs. The positive charges prefer to accumulate and migrate on the XLPE side. The homo-charges at the interface always remain on the EPDM side. The number of negative charges is higher than the number of positive charges at the interface. The bipolar interfacial charges are ascribed to the charge transfer process that occurs at the interface because of the energy level alignment that is revealed by the electronic energy structures of XLPE and EPDM. The trapping sites, along with the charge injection and transport, contribute to the interfacial charge behavior.
ISSN:1070-9878
1558-4135
DOI:10.1109/TDEI.2019.008122