Al doping effect on electrical and dielectric aging behavior against impulse surge in ZPCCYA-based varistors

Al doping effect on electrical and dielectric aging behavior against impulse surge in the ZPCCYA-based varistors was investigated. The clamp ratio (K) decreased in accordance with increasing Al2O3 content up to 0.005 mol%. A further increase in Al2O3 doping level caused K to increase. The K value at a surge current of 5 A and 10 A for the varistor doped with 0.005 mol% Al2O3 exhibited 1.49 and 1.57, respectively. Furthermore, the K value at a higher surge current of 1200 A was 2.44 for the varistors doped with 0.005 mol% and 0.01 mol% Al2O3. The best electrical and dielectric stability against impulse surge current of 1200 A was obtained at 0.01 mol% Al2O3, where %ΔE1mA/cm2 = -1.0%, %Δα = 0%, %ΔJL = -3.9%, %Δε'APP = +1.4%, and %Δ tan δ = -10.5%. Conclusively, Al2O3 content was optimized at 0.01 mol% in terms of the surge absorption capability.