Effect of Sc 2O 3 on the electrical properties of (Co, Ta, Cr)-doped SnO 2 varistors

Abstract

The effects of Sc 2O 3 doping on the electrical properties of (Co, Ta, Cr)-doped SnO 2 varistors were investigated and the maximal nonlinear coefficient ( α = 34 ) of the sample doped with 0.03 mol% Sc 2O 3 was obtained. It was found that the breakdown electrical field of samples increased significantly with increasing Sc 2O 3 concentration and the sample doped with 0.08 mol% Sc 2O 3 has the highest breakdown electrical field of 3336 V/mm. The measurement of grain size and sample impedances reveal that the increase of grain boundary resistance is the substantial reason for the increase of breakdown electrical field. The increase of grain boundary resistance may be caused by the increase of depletion layer thickness and it can be illustrated by the decrease of relative dielectric constant with increasing Sc 2O 3 concentration.