Thermal-electrical breakdown of disordered conductor-insulator composites

We present the first observations of 'thermal-electrical breakdown' in diso rdered conductor-insulator composites with a hi,oh electric field. This dif fers from simple electrical breakdown governed by local heat. When a large current hows through the most conductive pathway in a composite, the constr iction of the current at the most electro-resistive point in the pathway in creases the Joule heal dissipation, and a localized thermal-electrical doma in 'hot spot' appears on the composite. The thermal-electrical breakdown of the disordered conductor-insulator composite results from the local conduc tivity; the hot spot starts at the most resistive point on one,of the most conductive pathways and the breakdown progresses as the hot spot evolves.