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

Abstract 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.