Efeito da adição de alumina nas características elétricas de varistores à base de óxido de zinco (ZnO).

Abstract

The effect of the addition of alumina (0.005 mol %) on the varistor electrical characteristics of the systems: a) 96 ZnO. 3Bi²O³. CO³O² (mol %); b) 98.5 ZnO. Bi²O³.0.5 CO³O£ (mol %); c) 95ZnO.. 3Bi²O³.CO³O£.MnO2 (mol %) and d) 98 ZnO. Bi²O³.0.5CO³O£.0.5MnO (mol %) was analyzed in samples synthesized at 1000°C, 1100°C and 1150°C. For systems "a" and "d" a drop in electrical characteristics was observed. In the case of the "a" system, it must have been probably caused by the inhibition of grain growth by excess Al³+ ions; and in the case of the "d" system, microstructural analysis becomes necessary. Systems "b" and "c" show a considerable improvement in non-ohmic behavior. In the case of system "b", to justify this improvement, a microstructural analysis is necessary. In the "c" system, the effect can possibly be attributed to the increase in resistivity at the grain boundaries.