INTEGRATED ELECTROCERAMICS - DENSIFICATION AND STRESS DEVELOPMENT IN SOL-GEL DERIVED THIN-LAYERS

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