Towards new levels for stacking of sol-gel functional coatings

High optical performance coatings prepared by a liquid deposition process have been studied with focus on the parameters playing a role on the layer stacking ability. During the development of multilayer optical coatings, defects such as cracks, scattering and a refractive index gradient could appear. In order to understand the origins of these limitations, the investigation was performed on colloidal stacks of single and multi-materials. This study has rendered it possible to define the main process parameters as well as the physical and chemical parameters of the suspensions influencing the stacking capacity. This work is a first step to obtaining evidence of a relationship between the thin film microstructure induced by deposition conditions and the ability to achieve sol-gel thick films with good optical (homogeneous) and mechanical (crack-free) properties.