Abstract
The degradation behavior against pulse–current stress and the stability against DC accelerated aging stress of Na2CO3 doped ZnO-based varistor ceramics were investigated in this work. The results showed that the breakdown field E1mA/cm2 and the nonlinear coefficient (α) decrease with the increasing of the content of Na2CO3. The EDX analysis confirmed that the doping of Na ions into ZnO grains can enhance the electron concentration in grains and restrict the migration of zinc interstitials. The varistor with 0.06mol% Na2CO3 sintered by two-step exhibited the best performance for clamp characteristics and stability against DC accelerated aging stress. The clamping voltage ratio K against pulse–current stress of 3500–5500A was 2.11–2.29, and the variation rate of the breakdown field (%ΔE1mA/cm2) was only −0.2, in addition, the variation rate of the nonlinear coefficient α was −0.3 for DC accelerated aging stress of 0.9E1mA /120°C /8h.
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