Electrical properties of micro-composites SiC-β′SiAlON under high electric fields, in relation to surface morphology

This study describes the electrical behaviour of SiC-beta'SWON granular composite materials under pulsed high electric fields. Such composite materials favour enhanced discharge on surface and the global electric field required for the discharge is very reduced compared with a similar air gap at the same atmosphere pressure. It is shown that the electrical discharge proceeds with successive steps and the most important one is the local ionisation of the air atmosphere. At the macroscopic scale, ionisation mechanisms are approximated to the Paschen's law and at the microscopic scale, breakdown follows the Fowler-Nordheim's law for the enhanced field emission at SiC grain boundaries. The global electrical properties vary against the surface morphology since the number and shape of macroscopic sites for surface ionisation highly influence the breakdown mechanism. (c) 2005 Elsevier Ltd. All rights reserved.