Influence of Multiple Trapping Phenomena on The Applications Criteria of ZnO-Bi2O3-Based Varistors

The performance characteristics of the ZnO-Bi2O3-based varistors can be assessed to meet the applications criteria on the basis of a systematic evaluation corresponding to various experimental conditions. This evaluation process employs the lumped parameter/complex plane analysis technique for the ac small-signal immittance data. An overall behavior of these devices is attributed to the microstructural effects via controlled grain-size and its distribution, existence of phases, carrier density in the grains, trapping states, and their role within the electrical thickness across the grain-boundary electrical barrier, etc. These factors are strongly dictated by the additives to ZnO in conjunction with the processing variables. Multiple device functions can result when a single set from a variety of processing parameters is chosen, provided the starting chemistry or composition/formulation remain invariant. The factors related to materials' history, composition recipe, and combined processing methods influence or modify relative magnitudes of the constituting elements of each trapping relaxation. Thus, these magnitudes either increase or decrease the visibility without distorting the devices' generic dielectric behavior. An identical set of experiments contributes to distinguish a good varistor performance over a poor response for surge arrester (i.e., suppressor/absorber) applications in the power systems' transient protection