Estudo do efeito do óxido de silício nas propriedades elétricas e na microestrutura de varistores de ZnO.

Abstract

The present work deals with the influence of silicon oxide (SiOj) addition in the ZnO Bif>3 .Co304 .Mn02 Sb2Oj varistor system. The isolated and combinated action of this oxide upon the electrical properties and microstructure alteration in the ceramics samples sintered in different temperatures were investigated. Electrical characterization, was done by measures of current density versus the applied electric field and rmcrostnictural and ceramic phase characterization were conducted scanning electronic microscopy (MEV) and X-ray dinractometry (DRX). The quinary varistor system (ZnO .BijOj .Co304 .Mh02 .Sb2Oj) with and without addition of silicon oxide (SiOj) were characterized by observing the fi-BijOj, P-Zt^SbjO^ (spinel) as well as ZnO phases. An alteration of these phases as a function of sintering temperatures and dopant (SiOj) employed which in turn provoked changes in microstructure as well as the electrical characteristics of the systen were observed. It was shown that addition of small quantities of silicon oxide inhibited grain growth, help the formation of a homogeneous microstructure.