Advances in the study of the conduction modes in tin dioxide based varistors

R. PARRA; M.A. PONCE; C.M. ALDAO; M.S. CASTRO

Toledo, España

Congreso; Electroceramics X; 2006

CSIC - Sociedad Española de Cerámica y Vidrio

The microstructure of the SnO2.Co3O4.Nb2O5.La2O3 varistor system prepared through the conventional mixture of oxides route was characterised. The electrical breakdown field (Er) and the non-linear coefficient a were determined from plots of the current density (J) as a function of the electric field (E). Assuming the formation of Schottky barriers at the grain boundaries and conduction to occur due to tunnelling and thermionic currents, the barrier height and donor concentration were obtained by fitting the experimental data from impedance spectroscopy (IS) analyses. The determined barrier height and donor concentration were employed to establish a discussion on the main conduction modes that rule the behaviour of tin dioxide varistors. It was found that the current due to tunnelling across voltage barriers resulted to be several orders of magnitude higher than that of thermionic emission.