Ebrahim Amoupour - Department of Electronic Engineering, Roudsar & Amlash Branch, Islamic Azad University, Roudsar, Iran

doping with other metal oxides are ZnO varistors. ZnO varistors ceramic pieces are more complex than solids, Includes Characteristics of the voltage – current are highlynonlinear - the same anti-parallel Zener diodes are[2]. The threshold voltage (breakdown voltage) with a high resistance and then, voltage and resistance severely reduced so varistors act as a conductor[3]. Zinc oxide alone is an N-type semiconductor, the voltage behavior - the linear and various metal oxides as additives for non-linear characteristic of a voltage - current use. Absorbing them as fast unstable voltages and high voltage transient, Stabilizing voltage in electric systems and electronic circuits are used as a sudden transient voltage regulator is used. To protect the electronic equipment, due to low prices and access are very important. Bi2O3 and TiO2 oxides of zinc oxide added to them. Then we double sintering. Because the random orientation of crystals during a sintering causes, ceramics have characteristics that arehomogeneous in all directions. This feature can be homogenous with specific procedures during sintering or cool to room temperature changed. Many of the unique properties of ceramics direct result of the small crystal properties, their orientation relative to each other or grain boundaries between them[4, 5]. The small crystals with random orientation are grain to say so. Grain boundary area between the so-called thin layer is depleted the electrical conductivity of this layer is less than the grains themselves. As a result, there is an inverse relationship between resistivity and grain size[2]. In other words, the grain structure of zinc oxide is surrounded by a thininsulating dams have. The nano-powder with zinc oxide and additives (including oxides of bismuth, antimony, chromium, cobalt, nickel, etc.) synthesized zinc oxide made tablets lightning rods. Tablets of the surge arrester made Microstructure under test and Electrical measurement and underwent X-ray and SEM. After the final sintering nonlinear coefficient and breakdown voltage were investigated.

varistors ceramic; non-linear voltage; ZnO