Nature of the Schottky-type barrier of highly dense SnO2 systems displaying nonohmic behavior

The electrical characteristics of highly dense ${\mathrm{SnO}}_2$ ceramic varistors are believed to be caused by the existence of potential barriers at the grain boundary. A complex plane analysis technique (to eliminate the influence of trapping activity associated with the conductance term observed via depression angle of a semicircular relaxation in the complex capacitance plane), allied with an approached Mott–Schottky model, are used to demonstrate that the potential barriers at the grain boundary are Schottky-type barriers in ${\mathrm{SnO}}_2$ varistors such as those observed in the traditional ZnO varistor.