Percolative breakdown model for ceramics based on a random grain-boundary network

The mechanism of intrinsic breakdown in ceramics and insulating polymers is not clearly understood. A common feature in these materials is the existence of internal grain boundaries that provide a natural barrier to conduction. Here we propose that external electric fields work to alter the barrier heights at the various grain boundaries (GBs). A dynamic model for current conduction in ceramics is developed. This random Voronoi network of grains can model percolative paths through the sample, the overall current-voltage characteristics, and estimates effects of variations in grain size.