Relation between nonlinearity and semiconducting characteristics of SrCoO₃ additive in ZnO varistors sintered in a reducing atmosphere

Abstract

Air-sintered SrCoO₃ is strongly reduced at 1020°C in P_O2 = 1.6 × 10⁻⁹ MPa and then post-annealed at various temperatures in air. The conductive and structural characteristics are examined, comparing them with those of air-sintered. Although annealing in a reducing atmosphere breaks down SrCoO₃ to several compounds, SrCoO₃ is re-synthesized by post-annealing above 800°C. When post-annealed at 1000°C, the oxidation state of SrCoO₃ is believed to be the same higher level as that of sintered in air. The result shows that, enhancement of p-type carriers in SrCoO₃ at grain boundaries leads to nonlinearity improvement of SrCoO₃-doped ZnO varistors sintered in reducing atmospheres.