Resumo

AGUILAR-MARTINEZ, J.A et al. Effect of Cr₂0₃ on the microstructure and non-ohmic properties of (Co, Sb)-doped SnO₂ varistors. Rev. mex. fis. [online]. 2013, vol.59, n.1, pp.6-9. ISSN 0035-001X.

The effect of Cr₂O₃ addition on the physical characteristics, microstructure, and current-voltage properties of (Co-Sb)-doped SnO₂ varistors was investigated. SnO₂-Co₃O₄-Sb₂O₅ ceramics with additions of 0.0, 0.03, 0.05 and 0.07 mol % Cr₂O₃ were sintered at 1350 ^oC under ambient atmosphere and characterized microstructurally and electrically. The characterization by XRD and SEM show that the microstructure remains as a single phase material with multimodal size distribution of SnO₂ grains. The greatest effect of Cr₂O₃additions is manifested in the electric breakdown field. Additions of high levels (0.07 and 0.05 %) of this oxide promote an increase of approximately 55% in this parameter compared to the Cr₂O₃-free sample. Another physical property is affected: the measured density values decreases as the Cr₂O₃ content increases. A change in the nonlinearity coefficient value is produced only at the highest Cr₂O₃ content while at intermediate levels there is not change at all. Consequently, when seeking high nonlinearity coefficients, intermediate levels of Cr₂O₃ are not recommended.

Palavras-chave : Varistor; breakdown voltage; nonlinearity.