Integrated electroceramics: densification and stress development in sol-gel derived thin layers

Abstract

The densification behavior of sol-gel derived thin layers was examined. Two model system were chosen: an acetate/alkoxide (lead titanate) and an alkoxide/alkoxide (lithium niobate) system. Drying, pyrolysis and shrinkage which occur on heat treatment were systematically analysed by in-situ ellipsometry and stress measurements. A linear shrinkage of ∼40% was observed normal to the substrate with little change in thickness above 200–250°C. The shrinkage behavior was different from bulk gels. The large stresses which developed on heating and cooling in thin-layer form result from drying of the constrained layer, shrinkage during pyrolysis and from thermal expansion mismatch between the deposited layer and the substrate. The evolution of stress is discussed in terms of shrinkage data, and differences between the two material systems are reported.