Papers by Author: E.G. da Costa

Abstract: The zinc oxide varistors are ceramic semiconductor devices doped with some metallic oxides such as: bismuth, nickel, manganese, cobalt, and others. The aim of this work is to characterize the varistors, obtained by the Pechini’s method, regarding their microstructure and electrical features. By using chemical synthesis, it has been produced ceramic powders. The powders have been compacted in the form of pellets and sintered at 1200°C/1h. The samples have been characterized by measurements of J x E, XRD and by SEM. The results show that the powders obtained through Pechini’s synthesis method and calcined at 700°C/1h have a particle size of less than 100 nm. The resulting microstructures show heterogeneous morphologies in a shape of pins and presence of inter and intragrain porosity. The electrically characterized results show that the produced varistors present a nonlinearity coefficient of 21 and breakdown voltage of 1590 V/cm.