Degradation mechanisms of barium titanate based thick film capacitors

Abstract

The electrical characteristics, including degradation, of high K (≅ 500) barium titanate based thick film capacitors were studied. It was found that a gold conductor made from Au metallo-organic paste is not compatible with the porous high K dielectric material. The leakage current of a thick film capacitor made from Ag/Pd thick film conducting paste and high K dielectric has shown ohmic and space charge limited current behavior with a 3/2 power voltage dependence. Voltage independence of thermal activation energy and time dependence of a leakage current have been observed. A healing effect by reversal of bias polarity and humidity effect on leakage current have also been studied. The 3/2 power voltage dependence can be attributed to point emission from surface indentations or clusters of Ag particles at the electrode. Two possible degradation mechanisms based either on simple vacancy movement or a reduced grain boundary potential barrier height are suggested. It has been found that an electronic conduction model based on reduced grain boundary barrier height is more reasonable than that of simple vacancy induced current model.