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A number of recent studies have been devoted to problems concerning storage and transport of electronic charges in polymers. Of particular interest are questions relating to the transport of charge carriers in thin films of highly insulating polymers. In general, charge transport is studied by measurements of external integral parameters such as the decay of the surface potential. These quantities...
Several polar and non-polar polymers, including polyvinylidene fluoride, polyethylene and polytetra-fluoroethylene were charged by evaporating various metal electrodes onto films of the materials and applying electric fields of the order of 1 MV/cm at various temperatures and times. The charged films were then analyzed by observing the charge transient which results during thermal equilibration following...
Several papers1–4 have reported on the measurement of the mean depth of charge distributions in dielectrics. Recent publications by Collins,5,6 Laurenceau et al.,7,8 Sessler et al.9 and Andress et al.10 are directed towards the determination of the detailed spatial charge distributions. In a very recent letter DeReggi et al.11 showed that the thermal-pulse technique only delivers the first 10–15 Fourier...
Whitehead1 reviewing early work quotes that Kohlraush as early as 1845 suggested the decay current formula i = a.t−n and surprisingly the physical reasons for this relationship still remain the subject of discussion. For electronic conductors, Walden2 and Wintle3 have provided extensive evidence that the discharge currents are mainly due to trapped space charge in the region around the electrodes...
During the last few years, many powerful methods for studying the storage and polarization processes in dielectrics have been developed. They are essentially based on the analysis of the time or temperature dependence of the charge or polarization stored in the material. This has led to the knowledge of phenomenological parameters (trap depths, activation energies, carrier lifetimes, etc.) which are...
Electron irradiation in a good dielectric, such as a Teflon polymer, both deposits electrons in the material and, simultaneously, induces significant conductivity. Considerable work has been done to understand the resulting transient (e.g. see refs. 1–7) and steady-state charge behavior (e.g. see refs. 8 and 9). Most theoretical studies have assumed uniform, time-indëpendent, induced conductivity...
Decay of induced current in low density polyethylene (density, 0.920 g/cc) was investigated after irradiation with a partially penetrating monoenergetic electron beam of 0.8 MeV. The values of the mobility of free electron under irradiation were estimated using the analysis of Gross et al.1 The relation between charges injected into polyethylene and the values of the decay current was also investigated.
Important in any practical use of electrets is the charge retention time and therefore device lifetime. Since charge retention times are on the order of years for many electret materials, accelerated tests are used where the driving force is increased temperature. In this preliminary study, three tests were used all using elevated temperatures: short-circuit thermally stimulated current measurements...
Localized electronic charges in disordered solids can be described in terms of ions. The transfer of charge to and from electrodes corresponds then, to the oxidation/ reduction of molecular species. The study of these charge injecting redox processes forms a fundamental and growing segment of electrochemical research. The theoretical bases for these studies are deceptively concise and are briefly...
In several kind of Polymers such as Polyethylene1–2 or Poly(vinylidene fluoride),3 we have observed, by Raman and infrared spectroscopy, rather important structural changes during the polarization process by a high electrostatic field. This effect is a function of the intensity of the poling field and it is generally emphasized by a thermal treatment during the polarization.
“The subject (of the anomalous properties of dielectrics) is somewhat special and one which until quite recently has not attracted the interest which it deserves from electrical engineers. There is an important relation between the anomalous properties of dielectrics and the performance of high voltage insulation. The literature on the subject reveals an enormous quantity of experimental results and...
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