Processing and Electrical Characterization of a Varistor‐Capacitor Cofired Multilayer Device

A comprehensive study of the materials selection, processing, cofiring, and electrical characterization of a multilayer varistor/capacitor (MLVC) device has been presented. The goal was to achieve component miniaturization and provide superior high‐frequency and high‐amplitude transient‐voltage protection. A ZnO‐based material and 0.75Pb‐(Mg 1/3 Nb 2/3 )O 3 ‐0.25Pb(Zn 1/3 Nb 2/3 )O 3 (PMN‐PZN) were chosen as the respective varistor and capacitor components. Using a controlled‐profile furnace, PMN‐PZN with excess PbO resulted in an optimum cofiring with a complex varistor composition. The sintering study made it clear that the ability to cofire is dependent not only on matching sintering temperatures and final densities but also sintering rates. Composite‐pellet studies assured the mechanical and electrical integrity of the device and indicated that interaction between the respective components was minimal. Prototype MLVC devices were fabricated using standard tape‐casting techniques. Microstructural analysis of the MLVCs revealed solid ceramic/ceramic and ceramic/electrode interfaces with little evidence of interaction. Current‐voltage and dielectric measurements both indicated good electrical properties that can be specifically tailored by changing the layer thickness.