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Imprint effects are studied in Poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) metal-ferroelectric-metal (MFM)-capacitors. Imprint refers to a degradation mechanism in ferroelectrics which is found to take place on a logarithmic time scale. We present that the displacement of the polarization hysteresis loop along the voltage axis, the switching time, the polarization and the capacitance...
Polarity reversal transient currents in cellulose acetate films have been studied as a function of field, thickness and temperature. The current peaks have been observed in the current-time characteristics and these peaks may be attributed to the space charge injection from electrodes. The dependence of the transient current on thickness (I α d−3)of the sample justifies the existence of SCLC. The...
Carrier mobility measurements have been performed on PVDF films using a variety of techniques including step-voltage current transients, steady-state conductivity values. The polarity-reversal technique and the voltage-ramp method. The range of mobilities obtained at 70°C was from 3.9 × 10−14 cm2V−1s−1 to 1.2 × 10−7 cm2V−1s−1 depending on the theory employed, which served to demonstrate the ambiguity...
Thin films of ion conducting polyethylene oxide (PEO) are investigated as model systems for a solid electrolyte. Metal-PEO-metal capacitance structures show a pronounced relaxational behavior with a sample thickness (length) dependent effective dielectric permittivity caused by a space charge polarization of mobile ions.
Voltage reversal will strongly affect the stability of cable in service, especially under temperature gradient due to the temperature rise of the cable. In this paper, the results of space charge profiles and field distortions in low density polyethylene (LDPE) films after dc pre-stress of 50 kV/mm for 2 h under temperature gradient and then during different voltage reverse polarities or during different...
A system has been developed by the authors to attempt to measure the surface conductivity of a large high voltage gas-filled switch housing. The housing is a hollow cylinder with an internal diameter of 300 mm and has a wall thickness of 25 mm. Unlike the situation with thin films where it is possible to perform meaningful surface conductivity measurements by creating a well defined field parallel...
Influence of thickness in LDPE sheet on electrical field distortion and transient external current under dc step voltage are studied. Temporal change in space charge distribution in LDPE sheets of 100, 200 and 300 mum in thickness are measured by PEA method with evaporated A1 electrode or semiconduction rubber electrode under a mean applied field of 1 MV/cm. No temporal changes in space charge distribution...
A persistent internal polarization may be producted in semicrystalline polyethylene by continued electrical stressing. The polarization originates from the alignment of impurity dipoles and or an accumulation of space charges in localized states. Distinguishing between these two sources when making measurements of the remnant polarization requires that the basic characteristics of these two polarization...
A one dimensional drift dominated conduction model is used with a flowing charged dielectric to describe the transient and dc steady state electric field and space charge distributions. This work extends past similar work1 but now allows for forced convection of the liquid dielectric in the same or opposite direction of the electric field resulting in convection currents as well as conduction and...
Closed form steady state solutions are developed for one dimensional unipolar drift-diffusion conduction between parallel plate electrodes. Under time varying conditions, a mathematical transformation converts the governing non-linear partial differential equation to a linear but non-homogeneous diffusion equation. Typical steady state and transient electric field and charge density distributions...
When sufficiently high voltages are applied to electrical insulators, electrical breakdown occurs at some time after the voltage is applied. This time delay to breakdown coupled to time of flight measurements of charge carrier mobilities obtained from peaks in the current waveform, provides information on insulation and conduction characteristics of the dielectrics. In addition, the bulk electric...
Many liquid dielectrics, when stressed by high electric fields, support bulk space charge distributions. To model such conduction processes, recent work1 has used a unipolar ion mobility conduction model similar to that used for solid state semiconductors, where the velocities of charge carriers injected from an emitting electrode are proportional to the electric field and in turn the electric field...
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