Improved varistor nonlinearity via sintering and acceptor impurity doping

¹ Physics Department of Shandong University, Jinan Shandong 250100, P.R. China
² The Thunder Defense Center of Shandong, Jinan Shandong 250100, P.R. China

Corresponding author: xjwangyj@chinaren.net

Received: 4 February 2000
Revised: 19 April 2000
Accepted: 9 May 2000
Published online: 15 September 2000

Abstract

A new varistor system of SnO₂-Bi₂O₃-Nb₂O₅ was reported in this paper. The electrical field-current density characteristics of this system were investigated by doping different amounts of Bi₂O₃ and sintering the samples at various temperatures. It is found that adding 0.75 mol% Bi₂O₃ to Nb-doped SnO₂ ceramic resulted in maximum nonlinear coefficient and breakdown voltage with α = 14 and E_0.5 = 19 525 V/cm. To improve the density as well as the nonlinearity of this system, different amounts of Co₂O₃ were added. The optimal conditions for the best nonlinearity were 1300 °C with 0.03 mol% Co₂O₃ addition. Deviation from this doping content, toward either higher or lower Co₂O₃ content, causes the deterioration of I−V characteristics. It can be concluded that the incorporation of cobalt oxides into SnO₂-based varistors improves the nonlinearity in the low and intermediate current density regions because of the increased barrier height . The experimental results were explained with the defect barrier model for SnO₂-based varistors.