We performed a comparative study of electrical and thermal properties of ZnOand SnO2-based varistor. The electrical properties of commercial ZnO-based varistor are equivalent to that found in SnO2-based varistor system. In spite of this, the SnO2 showed a thermal conductivity higher than commercial samples of ZnO-based varistor, which allied with its simpler microstructure and lower dopant conc...

After a brief review of varistor fundamentals, including a discussion of the infamous " speed of response " issue, the report describes several unconventional packaging implementations of varistor material (usually a flat disc between metallized electrodes), such as molded axial package, bulkhead connectors, coaxial mounting, reconstituted material, and varistor substrates with surface conducti...

The microstructure and nonohmic properties of SnO₂-Ta₂O₅-ZnO varistor system doped with different amounts of ZrO₂ (0-2.0 mol%) were investigated. The proposed samples were sintered at 1400°C for 2 h with conventional ceramic processing method. By X-ray diffraction, SnO₂ cassiterite phase was found in all the samples, and no extra phases were identified in the detection limit. The doping of ZrO₂...

A model for a semiconducting ceramic material used in devices to protect electrical equipment against overvoltages is presented. The fine structure in the material induces highly oscillating coefficients in the Maxwell equation. Maxwell equations are homogenized to obtain a coupled system. The fine scales in the model yield a local problem coupled with the homogenized Maxwell’s equations. In th...

− High voltage varistors that consist of grained ZnO have to be tested before assembling. The recommended method for standard industrial testing of varistors demands application of high voltages and intensive currents that is inconvenient and needs extensive power consumption. Nondestructive methods for varistor quality and endurance evaluation have been proposed. They rely on the application o...

In the ZnO based varistor, the improvement of nonlinear coefficient (α) and prevention of evaporation of Bi2O3 during heat treatments can be achieved by the addition of MnO2 or Co3O4. In this conjunction, it is proper to see the effect of these additives at different low mol percentage and sintering conditions to nonlinear coefficient improvement of the varistor ceramics. In this paper, the inv...

The paper presents a comparison of the performance of voltage-switching devices and voltage-limiting devices for late seventies-vintage SPDs as marketed and installed in service panels in the USA and in Europe. Artifacts in the response of a typical oscilloscope to a nearby gap sparkover, and the effect of lead dress inside the panels and outdoor installation are described. Predictably, the per...

This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spect...

A range of varistors, in terms of break down voltage, is required to protect integrated circuits, automotive systems and other modern electronics against transient over-voltages. There is a progressing need for the development and advancement of rugged and reliable varistor capable and proficient of working in harsh and callous environment like automotive industry where greater than before use ...

Composite films on the base of ZnO with different weight percentages of polypyrrole have been prepared using the hot pressing method and their current-voltage characteristics have been studied. Results show that the films have nonlinear varistor behavior and can be used to protect sensitive circuits from 110V up to 350V overvoltages. It is found that the higher the content...