Estudo do efeito do óxido de titânio nas propriedades microestruturais e elétricas de varistores à base de ZnO.

Abstract

In this work the titanium oxide influence on the electrical properties of varistor system (ZnO.Bi2O3.MnO2.C03O4) was studied. This system was sinterized at 1150°C, 1200°C and 1250°C during 1 hour. The electrical characterization was made by measurements of current density versus applied electrical field. On the other hand, the microstructural and ceramic phases characterizations were made by scanning eletronic microscopy and X-ray pattern observations. The varistor system containing 1,0% mol of T i 0 2 and sinterized at 1150°C showed the best electrical properties. The enhancement electrical properties is due to microstructural change caused by T i 0 2 addition. It was observed a decreased electrical properties in the systems sinterized at 1200°C and 1250°C. Microvoides and heterogeneous grains dimensions probably has negative influence on the varistor properties. The Zn2Ti04 phase formation was observed when to the system sinterized at 1200°C and 1250°C were additioned 0,7 e 1,0% mol of T i 0 2 . This phase that is conductor, may be affect negatively the electrical and microstructural characteristics of the samples.