Influence of Microstructure and Chemistry on the Electrical Characteristic of ZnO Varistors
The ZnO voltage limiter or varistor1 has an outstanding nonlinear current-voltage (I-V) characteristic and, as such, is used extensively to suppress the transient voltage surges encountered in the lightning and switching surges.2 The advancement in the state-of-the-art of the varistor in recent years3−9 makes it impossible to describe all the elements of this development within the scope of this paper. The objective of this paper is to concentrate on the microstructure and chemistry of the ZnO varistor and their effects on electrical properties. However, in order to appreciate this correlation, it is first necessary to briefly describe the current- voltage (I-V) characteristics of the varistor.
KeywordsHigh Current Density Depletion Layer Boundary Resistivity Nonlinear Region Intergranular Phase
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