Vapor diffusion of silver in cofired silver/palladium - ferroelectric ceramic multilayer

The mechanism of silver interfacial migration was investigated during cofir ing multilayer structures of Pb-based relaxer ferroelectric ceramics and Ag /Pd alloy electrode. A several-micron depth of silver diffusion could be co nfirmed by energy dispersive X-ray spectroscopy measurements. Scanning elec tron microscopy and transmission electron microscopy observations indicated that the silver migration was not attributed to a single factor. This invo lved the electrode composition, the sintering characteristic of the ceramic s, and the related sintering procedure. All these results have demonstrated that the vapor-phase diffusion via open pores on the surface of the cerami cs at the early period of sintering was the most important reason for the s ilver migration even though the migration along grain boundaries or into gr ains occurs at the final stage of sintering. Based on an evaporation-conden sation vapor-phase mass transport mechanism, a rate-controlled sintering pr ocess or a low-temperature sintering route of the materials was suggested t o effectively inhibit the interfacial diffusion of silver. (C) 2001 Elsevie r Science B.V. All rights reserved.