Development of thin-film nano-structured electrolyte layers for application in anode-supported solid oxide fuel cells

This paper reports a study on the deposition of sol particles for the preparation of thin and ultra-thin electrolyte membrane layers (thickness < 5 μm–50 nm), which cannot be produced with regular powder-based processes. For the deposition process, a range of coating liquids with varying particle sizes, covering the complete range between standard suspensions with a particle size of several 100 nm and nano-particle sols, was prepared. In the first part, it is demonstrated that a colloidal sol route can be used for membrane formation on a regular macroporous SOFC anode (NiO/zirconia), when the sol particle size is adapted to the pore structure of the anode (particle size ∼ 200 nm). SEM characterization indicated a thickness in the range 3–4 μm after calcination at 600 °C and ca. 2 μm after sintering at 1400 °C, far below the limit for conventional powder-based deposition methods. In the second part, ultra-thin zirconia and ceria membrane films are prepared by spraying sols containing nano-particles (average size 5–6 nm). The layers show a thickness of ∼ 100 nm, a very narrow particle size distribution and tight ultra-microporous structure, which allows a sintering treatment below 1000 °C, and can be used as an additional electrolyte layer for improving the leak rate of the cell or as diffusion barrier.