Abstract

GLOT, A. B.; LU, Z. Y.; ZHOU, Z. Y.  and  IVON, A. I.. Electrical properties of SnO₂ ceramic varistors withstanding high current pulses. Superf. vacío [online]. 2011, vol.24, n.2, pp.61-67. ISSN 1665-3521.

Electrical properties of new dense SnO₂-CoO-Nb₂O₅-Cr₂O₃-Y₂O₃ varistor ceramics are studied. Current-voltage characteristics in the wide range from 10^-11 to about 3.3·10³ A·cm^-2 contain three regions. At low currents linear (Ohmic) region is found. Highly nonlinear region with the nonlinearity coefficient of about 50 at 1 mA·cm^-2 is observed between 10^-6 and 1 A·cm^-2. At higher currents the upturn region is revealed. In this region the slope of current-voltage characteristic in the double logarithmic scale is decreased. The increase in dc current on time at fixed voltage and the hysteresis in the ac current-voltage characteristic are observed. These features can be related to Joule heating or electronic processes. However, after the high-current pulses only minor changes at low current are found. This indicates that studied ceramics withstand high-current overloads. This fact can be attributed to the formation of quite identical electrically-active grain boundaries throughout a sample. The grain resistivities estimated from high-current pulse data are the lowest known up to now for SnO₂ varistors.

Keywords : Grain boundary; Non-Ohmic conduction; Potential barrier; Pulse stability; Tin dioxide; Varistor.