Nonlinear electrical properties of cobalt doped SnO₂·Ni₂O₃·Nb₂O₅ varistors

¹ Department of Physics, Shandong University, Jinan 250100, PR China
² Experiment Center, Shandong University, Jinan 250105, PR China

Corresponding author: changpengli@sina.com

Received: 22 March 2001
Revised: 30 May 2001
Accepted: 8 June 2001
Published online: 15 October 2001

Abstract

A new varistor system of SnO₂·Ni₂O₃·Nb₂O₅ exhibits the relative dissatisfactory physical and electrical properties. The effect of cobalt oxide on the properties of the SnO₂·Ni₂O₃·Nb₂O₅ varistors was investigated by measuring the densities, permittivities, the current-voltage properties and the properties of the defect barriers. It is found that the sample doped with 0.25 mol% Co₂O₃ exhibits the abnormal poorer electrical properties than the samples without Co₂O₃ dopants. However, the sample doped with 6.0 mol% Co₂O₃ exhibits the highest nonlinear coefficient () and reference electrical field ( V/mm), although the sample doped with 1.0 mol% Co₂O₃ exhibits the highest densities ( g/cm³) and permittivities. The sample with 6.0 mol% Co₂O₃ bears the highest barriers, but the sample with 1.0 mol% Co₂O₃ shows the narrowest barriers. The investigation of the sintering temperature shows that the samples sintered at 1450 °C exhibit the better physical and electrical properties. The results were discussed and the defect barrier model was also introduced to explain.