Advances in YSZ Coatings Prepared by Sol-gel Route. Applications to Fuel Cells or Thermal Barrier Coatings

摘要

The objective of this research is to develop a novel process for SOFC electrolytes and fully ceramic TBC to prepare yttria stabilized zirconia (YSZ) by both a sol-gel derived route and a dip-coating method. The research focuses on the development of a process compatible with industrial requirements in terms of cost and easiness to processing. The microstructure of dip-coated thick films is studied by varying the characteristics of an organic YSZ suspension (concentration, rheology) used as coating bath. The suspension was obtained by addition of a polymeric matrix in a stable suspension of YSZ powders dispersed in an azeotropic MEK-EtOH mixture. The obtained films are continuous, homogeneous and films thicknesses vary between 1 to 100 μm. Different microstructures are obtained depending on the synthesis parameters of the slurry composition. The microstructure of the films is found to depend on the YSZ precursor powders content and the polymeric sol/dispersant solution (EtOH-MEK) ratio. Finally, the dip-coated suspensions are used to prepare dense or porous layers according to the applications. The coating microstructure is engineered to decrease sintering ability, to be gas-tight for fuel cells electrolytes or to enhance thermal shock resistance for Thermal Barrier applications.