Praseodymium and aluminium oxide effect on the electrical properties of zinc oxide-based varistors

The zinc oxide-based varistors is a polycrystalline ceramic with a highly non-linear current- voltage characteristic. The conventional chemical composition of this material contains several metallic oxides such as the Bi/sub 2/O/sub 3/, Sb/sub 2/O/sub 3/, Mn/sub 2/O/sub 3/, Cr/sub 2/O/sub 3/...etc. With these oxides commercialised varistors with a threshold field of around 200 V/mm are obtained. The research aiming to increase the threshold field confronted a delicate problem: a decrease in the energy absorption capacity. The study of the electrical property behaviour of zinc oxide-based varistors containing Pr/sub 6/O/sub 11/ oxide permit to increase the threshold field up to 350 V/mm while keeping the energy absorption capacity. The praseodymium oxide effect in the material structure is explained by a potential barrier height increase in the grain boundary and the grain size homogenisation. This work consists of the sample fabrication with different doses of Pr/sub 6/O/sub 11/ and Al/sub 2/O/sub 3/ (9H/sub 2/O), the material characterization before and after degradation as well as interpretation with respect to the existing results.