Abstract
Glasses in the PbO-B 2 O 3 -Al 2 O 3 -BaO-CaO-SiO 2 system were employed as the dopant to ZnO varistors. The thermal stability of the varistor is enhanced with glass additives. The temperature coefficient of threshold field for the sample doped with 1 w/o glass (65 w/o PbO - 23 w/o B 2 O 3 - 12 w/o SiO 2 ) is 1 × 10 -4 /K as compared to 3.3 × 10 -3 /K for that of the undoped sample. The change in the temperature dependence of the field-current density characteristics is more related to the barrier height change than the refractory behavior of the glass employed. Heat treatment is very effective in recovering the degraded samples by providing the activation energy for the diffusion of Zn interstitials. The experimental results can be explained with a Schottky barrier model. © 1990 The Mineral,Metal & Materials Society,Inc.