Estudos das propriedades elétricas dos varistores de ZNO na região de baixas tensões aplicadas.

Abstract

In this work we studied the electrical and dielectric properties of a particular type of ZnO varistor for different AC and DC voltage requirements. For this, the electrical characteristics AC and DC and dielectric at industrial frequency were determined. Based on the obtained results, it was verified the existence of a dependence on the height and width of the potential barriers with the applied electric field. From this study, it was found that the increase observed for the DC resistive current or the resistive component of the AC current with the increase of the electric field, associated with the reduction of the potential barriers height. Thus, knowledge of these dependencies allows us to determine the electrical and dielectric characteristics of the varistor under consideration for the entire region corresponding to the low applied voltages, allowing the study of various phenomena associated with this type of varistor, such as thermal stability and degradation. . The results obtained from the experiments were in agreement with the results presented in the literature and with the ZnO varistors theory. The study of the dependence of charge carrier densities and surface states, responsible for the variation of the potential barriers width and height, with the applied electric field was carried out based on the model proposed by Hower & Gupta.