Experimental Study about the Sintering Temperature of a New Metal Oxide Varistor Material

Protection of any sensitive electric equipment against any type of overvoltage (including lightning applied on power networks) is a big challenge for power electronics. The most advanced and reliable devices used in order to perform this operation are metal oxide varistor based surge-arresters. These varistors are made of a mixture of different metal oxide, where the main ingredient (more than 80-90% as mass concentration) is ZnO. The real improvements of these devices could be performed only in reference with their manufacturing process, by introducing different additives, with particular influences on the electrical behavior of the semi-conductor material, especially on their non-linear relation between voltage applied and current response and on their heat absorption capability. There is no physical or analytical model in order to assess the influence of dopants (additives) on the main electrical characteristics as well as the importance of each parameter belonging to the manufacturing process. This article presents the influence of the sintering temperature on the main electrical parameters (opening voltage, non-linearity coefficient and electrical response characteristics) of two new varistor materials (with 2 and 5 additives).