Clarification of electronic properties of polymer-inorganic material interface and development of insulating composite materials for higher fields

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In practical insulating systems, polymer is used mostly in the form of a composite with fillers, it is important to study electronic properties of polymer-filler interface at high fields. in this study, the author used epoxy-alumna and epoxy-silica two-layer composite films as model systems to investigate the effect of a polymer-filler interface on electronic conduction by measuring photocurrents and thermally stimulated currents (TSC). The main conclusions obtained in this research are summarized as follows.(1) Holes transported from the epoxy layer in epoxy-alumina compositesAt high fields and low temoprature, most of holes in the epoxy layer can pass through the epoxy-alumina interface and move in the alumina bulk, increasing the conduction current in the alumina. This interfacial phenomenon can not be explained by the conventional Maxwell-Wagner model. At high fields and room temperature, the pohotoconduction is governed by the almina layer. These are well explained by the Maxwell- … More Wagner model.(2) Holes transported from the alumina layer in epoxy-alumina compositeAt low fields and low temperature, holes in alumina layer can pass through the interface and increase the conduction current in the epoxy. On the other hand, at high fields, photoconduction is well explained by the Maxwell-Wagner model. At room temperature, transport of the carriers from the alumina layer is blocked by the potential barrier at the interface and many of hole are trapped at the interface.(3) Holes transported from the epoxy layer in epoxy-silica compositesSimilar measurements were carried out on epoxy-silica composites. The same phenomena which can not be explained by the Maxwell-Wagner model as in the epoxy-alumina compoites were also observed in epoxy-silica composites at low and room temoerature. TSC measurements showed that holes were scarcely accumulated at the epoxy-silica interface. On the othe hand, most of electrons from the epoxy layer can pass through the interfece and increase the conduction in silica region.As seen from the above results, the electrical properties of epoxy-filler composites are greatly affected by the interfaces in various ways depending on applied field, temperature, carrier species, direction of carriers, mechanical stress and so on. Less