Correlation of microstructures with electrical performance of Ag-based metal electrode–PZT electroceramic interfaces

The microstructures of 8 model Ag-based electrode pastes, fired on to PZT using commercial firing schedules, have been examined using SEM with EDS, and the electrical performance of these systems investigated. The effects of three different bonding additives (Bi2O3, CuO, and a lead boro-aluminosilicate glass frit) were investigated both individually and together. The additives were found to be vital for good bonding. In unfritted systems eutectic reactions between the additives, the electrode Ag, and the PZT dominated the microstructural evolution, the loss of Pb from the ceramic being of particular importance. In fritted pastes the glass frit dissolved the Bi2O3, and was able to draw the CuO to the interface, allowing reaction to occur. Electrical testing showed the unfritted systems to exhibit increased dielectric losses at frequencies <10,000 Hz due to Pb loss resulting in interfacial polarisation.