Theory of electrical breakdown in ionic crystals

Abstract

If an electrical field higher than a certain critical strength F is applied to an ionic crystal, the insulation breaks down. If the temperature is above a certain critical value T 0 (usually of the order 100° C.), F decreases very rapidly with temperature, and the breakdown takes place some seconds after the application of the field. Wagner (cf. Semenoff and Walther 1928) has shown that in this case the breakdown is due to the Joule heat generated by ionic conduction, which causes local melting. For temperatures less than T 0 , on the other hand, the breakdown takes place in a time of the order 10 -8 sec. (Rogowsky 1928) and the variation of F with temperature is very much smaller than in the case of heat breakdown, The phenomenon in this case is referred to as electrical breakdown, any melting of the crystal being ruled out by the short times involved.