Impulse degradation behavior of Co-Cr-Al-Y-doped ZnO-Pr6O11-based varistors with sintering temperature

The degradation behavior against impulse-current stress of the Co-Cr-Al-Y-doped ZnO-Pr6O11-based varistors was investigated in accordance with sintering temperature. The clamp voltage ratio (K) for impulse current increased in accordance with increasing sintering temperature. The varistors sintered at 1300 °C exhibited the best voltage clamp characteristics, which the clamping voltage ratio was in the range of 1.49-1.57 at a low impulse-current region (5-10 A) and was in the range of 1.70-2.44 at a high impulse-current region (400-1200 A). The best electrical stability against multi-impulse stress for continuously 3 times 1200 A was obtained at 1350 °C in sintering temperature, where %ΔE1 mA/cm2=−5.0%, %Δα = −13.9%, and %ΔJL = −21.9%.