Trouble-free Operation of Ionic Dielectrics During Prolonged Exposure to Voltage

It is shown that, if the ionic dielectrics stay in the electric field for a long time, a substantial redistribution of the electric field strength over the dielectric thickness occurs due to the migration of weakly bound ions under the influence of the electric field. Usually, the most mobile types of ions are positive (e.g., sodium ions in glass), therefore, over time, a high-resistance region is formed near the anode, on which almost all the voltage applied to the dielectric drops. This provides strong electric fields and can lead to the breakdown. Quantitative estimates of the time course of this process are obtained. It was revealed that temperature is of decisive importance for the process under consideration. The result obtained seems to be interesting: for a dielectric such as alkaline glass, the time of its safe operation at a relatively low temperature (about 130°C) does not exceed several years. Obviously, this result should be taken into account when designing devices based on ionic dielectrics exposured to voltage.