India-doped zirconia multi-layered thin film synthesized by atomic layer deposition for IT-SOFCs: Synthesis and electrochemical properties

Abstract

This study is focused on the search of new electrolyte/cathode interface architecture for intermediate temperature solid oxide fuel cells (IT-SOFCs). India-doped zirconia (IDZ) thin multilayer with three different contents of indium oxide, allowing to pass from an ionic conductor (30 mol% of InO1.5) to an electronic one (80 mol% of InO1.5) are deposited by atomic layer deposition (ALD) technique on porous LSF cathode and dense substrates (Stainless steel, Si (100)) at 300 °C. The as-prepared thin layers are well crystallized without any subsequent annealing. Uniform, adherent and dense thin layers with high microstructural quality are obtained at low temperature 300 °C without post-deposition annealing. The deposit is perfectly followed the roughness of the porous substrate surface without penetrating into the pores. The study shows that the ionic conduction zone is even more extensive than in sintered pellets (55 mol% of InO1.5). The low normalized ionic resistance and activation energy confirm the good effect of the presence of composition gradient at the interface cathode/electrolyte which favor the passage of charge carriers within the intermediate layers of IDZ. The values of the relaxation frequencies are situated between those corresponding to the grain boundaries and those of the bulks of an IDZ pellet. The electrochemical performances of IT-SOFC with IDZ are improved by decreasing the ohmic resistance losses and the polarization resistance associated with oxygen reduction reaction.