Abstract: Influence of TiO₂, Co₃O₄, Cr₂O₃, Ni₂O₃ and MnO dopings on the microstructure and electrical properties of SnO₂-Sb₂O₃ based varistor ceramic materials was investigated. It is found that TiO₂ and Co₃O₄ are effective dopants for improving densification of SnO₂ ceramics. According to XRD analysis, Co₂SnO₄ crystal phase are formed by the reaction between Co₃O₄ and SnO₂, and TiO₂ is dissolved into the SnO₂ phase. Doping of Sb₂O₃ can improve the semiconducting processes of SnO₂ grains. Co-doping Cr₂O₃, Ni₂O₃ and MnO is efficient to improve the nonlinear property and surge current withstanding performance of the materials. The samples with a diameter of 14mm have a nonlinear coefficient (α) of about 50, a breakdown electric filed of about 350V/mm and a leakage current of less than 5μA, and the withstanding surge peak current of 8/20μs waveshape is about 2kA, which meet practical requirement.

Key words: SnO₂ varistor, densification, withstanding surge current test