(Sb2O3/Sb2O5)-doped SnO2–Co3O4–Cr2O3 varistors: The Sb2O4 in-situ formation and its influence over the electrical and microstructural properties

The present study aimed to systematically study the transitions and consequential effects of antimony oxide (Sb₂O₃ or Sb₂O₅) additions over the properties of a SnO₂-based varistor system. High energy ball-milling and conventional sintering were used to obtain the samples with the following molar composition: (98.95-X)% SnO₂ - 1% Co₃O₄ - 0.05% Cr₂O₃ - X% Sb₂O₃/Sb₂O₅ where X = 0, 0.05, 0.1, 0.2 and 0.4 mol%. The thermal analysis suggested the in-situ formation of Sb₂O₄ at ~450 °C from Sb₂O₃ or Sb₂O₅ during the sintering of mixed oxides. SEM, XRD, and electrical analysis revealed similar results by using Sb₂O₃ or Sb₂O₅; the addition of 0.05 mol% antimony oxide provides the foremost properties. The transition equations from Sb₂O₃ or Sb₂O₅ to Sb₂O₄ demonstrate equivalency in the amount of Sb₂O₄ formed. That fact, besides the results obtained, were used to discuss a reasonable route for Sb³⁺ and Sb⁵⁺ incorporation within the SnO₂ lattice.