Elaboration of ZnO Based Varistors and the Effect of the Rare-Earths on their Electrical Behaviour

摘要

In this work we suggest a technological participation to improve the electrical behaviour and the reliability of the polycrystalline non-linear electronic devices, ZnO, based varistor, to be used to protect the electrical and electronic systems against the sudden increasing of high voltage on Electrical loads. This work includes the effect of Rare-Earth Metals (Er, Ce, Pr, Y, Dy) on the reliability of the varistor, ZnO, for different temperature firing. The nonlinearity coefficient, a ( = d(dLnl)/(dLnl)),the leakage current, I, the threshold voltage Vs, the grains size, d, which separate the tow grains, are all responsible of the electrical behaviour of this material. On adding the impurities such as: Cerium (Ce), Yttrium (Y), Erbium (Er), Praseodymium (Pr), and Dysprosium (Dy) as a rear-metal earth, it is concluded that each of them is positively affect on the performance of ZnO, which lead to stability of the devices and improve electrical and electronic system's behaviour and reliability.