ELECTRICAL-PROPERTIES OF GRAIN-BOUNDARIES IN CERAMIC COMPONENTS FOR ELECTRONICS

Many oxides and carbides can be made semiconducting by doping. In polycrystalline materials, trapping of charge at the grain boundaries makes them insulating through the formation of double Schottky barriers. Several components like voltage arresters, PTCR thermistors exist which use this specific effect. The electrical properties of the interfaces are briefly presented. Then, the influence of the heterogeneity of the microstructure is discussed. In particular, it is explained why the sample becomes electrically homogeneous under an increasing applied voltage.