The preparation of a ZnO varistor doped with and its properties

ZnO varistors doped with Pr 6 O 11 – CoO – Cr 2 O 3 – Y 2 O 3 – Al 2 O 3 were prepared at different sintering temperatures and their properties were investigated. The average grain size increased to 4.3 – 11.3 μ m with the increase of sintering temperature. However, the sintering temperature does not have an effect on the sintered density. The breakdown field greatly decreased from 6327 to 1974 V/cm, exhibiting a wide voltage gradient with the increase of sintering temperature. However, the nonlinear coefficient was almost unaffected by the sintering temperature: it was in the range 43.7–41.9. The varistor sintered at 1350 ∘ C exhibited the highest stability against DC accelerated aging stress ( 0.95 E B / 150 ∘ C / 24 h ); the variation rates of breakdown field and nonlinear coefficient are −0.3% and −6.7%, respectively.