Impulse Degradation Behavior of ZPCCYE Varistors with Y2O3/Er2O3 Ratio

The nonlinear electrical properties and degradation behavior against an impulse-current of 400 A in the ZnO-Pr6O11-CoO- Cr2O3-Y2O3/Er2O3 (ZPCCYE) varistors were investigated with different Y2O3/Er2O3 ratios. The Y2O3/Er2O3 mole ratio has a significant effect on nonlinear electrical properties and impulse degradation behavior of the ZPCCYE varistors. The varistors added with Y2O3/Er2O3 = 0.5/0.5 exhibited the best nonlinear properties with 39 in nonlinear coefficient (a) and the best clamp characteristics, in which the clamping voltage ratio (K) was in the range of K = 1.62-2.18 at an impulse-current of 1-50 A. The varistors added with Y2O3/Er2O3 = 0.25/0.5 exhibited the best electrical stability, with %Delta E-1 mA/cm(2) = -5.6%, %Delta alpha = 6.7%, and %Delta J(L) = -14.6% against an impulse-current of 400 A. On the contrary, the varistors added with Y2O3/Er2O3 = 0.5/0.5 were destroyed applying an impulse-current of 400 A.