Abstract
We have measured AC-conductance (@50Hz) of ZnO varistor contained about 5mol% additives (Bi203, Sb203, etc.) and obtained the nonlinear conponent of current responses. Activation energy (Ea) was determined by Arrhenius-Plots of peak current values of the nonlinear responses. The Ea against Vp-p was almost constant in the low voltage region, and those in the high voltage region decreased steeply as increase of Vp-p. Ea was about 0.2 eV in the flat region, while the intercept of Ea regarding to the high voltage region was estimated to be about 4 eV by extrapolation of the straight line. We assumed that the intercept of Ea and the flat Ea were corresponding to barrier height at a thin grain-boundary along ZnO grains and activation energy of a thick grain-boundary of triple point neighbor, respectively.
