Highly stable nonlinear behavior against impulse current of ZnO–Pr 6O 11–CoO–Cr 2O 3–Y 2O 3 varistors

Abstract

The nonlinear electrical behavior against the impulse stress (400–1200 A) in the ZnO–Pr 6O 11–CoO–Cr 2O 3–Y 2O 3 varistors has been investigated with sintering time. The sintering time did have a significant effect on the clamp ratio, which exhibits a surge protection capability. The varistors sintered for 1 h exhibited the best clamp characteristics, in which the clamp voltage ratio was in the range of K = 1.61–1.92 at a lower impulse current region (5–50 A) and was in the range of K = 2.06–2.55 at a higher single impulse current region (400–1200 A). The best electrical stability against the multi-impulse aging stress of 1200 A was also obtained from the varistors sintered for 2 h, where %ΔE 1 mA =−1.6%, %Δα =1.3%, and %ΔJ L =−4.9%.