Inner Electrodes for Multilayer Varistors

Abstract

In the present study, Pt or AgPd metal is used as the inner electrode for Bi 2 O 3 -doped ZnO multilayer varistors (MLV). The growth of the ZnO grains is constrained by the presence of the inner electrodes. The Pt inner electrodes are chemically inert to Bi 2 O 3 -doped ZnO. The Bi 2 O 3 could react with Pd to form PdBi 2 O 4 . The Bi 2 O 3 -rich liquid also tends to wet the AgPd electrode. The size of ZnO grains in the MLV/AgPd specimen is larger. The ZnO grains in the MLV/AgPd specimen can even grow to a size larger than the layer thickness at the expense of electrode continuity.

Low‐Temperature Sintering and Electrical Properties of ZnO–Bi2O3–TiO2–Co2O3–MnCO3‐Based Varistor with Bi2O3–B2O3 Frit for Multilayer Chip Varistor Applications

“…The interfacial reactions between ceramic and inner electrodes during cofiring cause many disadvantageous influences on the electrical properties of multilayer ceramic devices 18,19 . To study the reactions between the varistor ceramic with 2 wt% BiBF and Ag electrodes, XRD patterns of the samples with 20 wt% Ag sintered at 900°C are shown in Fig.…”

ZnO varistor ceramics prepared by the reduction–reoxidation method

“…With the decrease of thickness of each layer and the increase of layer number, the proportion of inner electrodes in materials consumed by multilayer chip varistors is growing. Generally the sintering temperature of ZnO varistors is higher than 1000 • C, the alloy Ag/Pd (30:70) with a high melting point has to be employed as inner electrodes material [5][6][7][8][9] accounting for over 50% of the total cost. Many researchers and manufacturers are making great efforts to replace the Ag/Pd inner electrodes by the cheaper silver (Ag) inner electrodes [10,11], but the cost of Ag is still relatively higher.…”