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

The electrical characteristics of highly dense SnO2 ceramic varistors are b elieved to be caused by the existence of potential barriers at the grain bo undary. A complex plane analysis technique (to eliminate the influence of t rapping activity associated with the conductance term observed via depressi on angle of a semicircular relaxation in the complex capacitance plane), al lied with an approached Mott-Schottky model, are used to demonstrate that t he potential barriers at the grain boundary are Schottky-type barriers in S nO2 varistors such as those observed in the traditional ZnO varistor. (C) 2 000 American Institute of Physics. [S0021-8979(00)03823-8].