Electrical Properties of Multilayer‐Chip ZnO Varistors in a Moist‐Air Environment

Abstract

Multilayer‐chip varistors were prepared using the ZnO‐glass system by applying tape casting technology. The effect of processing conditions on the multilayer ceramic microstructure and electrical properties was studied. The location, size, and density of the pores within the multilayer structure were examined by scanning electron microscopy and the displacement method using distilled water. The experimental results showed that the electrical properties of a multiplayerchip varistor could be influenced substantially by the porosities associated with environmental moisture in the range ≅15%–95% relative humidity at 25°C. Such an effect can cause substantial current leakage as well as the separation of the I–V curves into four regions, i.e., pre‐breakdown, linear, breakdown, and upturn. A proposed pore model and equivalent circuit for the multilayer‐chip ZnO varistors. have been simulated with a commercial varistor and a serial resistance to demonstrate the observed I–V phenomena.