The sol–gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers

Abstract

a b s t r a c tSol-gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol-gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttriastabilized-zirconia (YSZ, 8% Y 2 O 3 ) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 m thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 • C.

Solid oxide fuel cell with a spin-coated yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolyte

“…As a fast and cost-effective technique, slurry spin coating has been widely used to prepare gas-tight oxide electrolyte lms. [18][19][20] Wang et al 21 fabricated a 10 mm-thick YSZ membrane on a NiO-YSZ anode support with slurry spin coating, and the maximum power density (P max ) of the single cell reaches 2 W cm À2 at 800 C. Chen et al 22 coated a 10 mm-thick anode functional layer (AFL) and a 5 mm-thick YSZ electrolyte membrane successively on a NiO-YSZ anode support, and the P max of the cell is 0.6 W cm À2 at 800 C. Many parameters of the spin coating process, such as the viscosity and solid content of the slurry, the spinning speed and duration, number of coating cycles and the property of AFL, have important effect on the thickness and porosity of the electrolyte layer. A higher spinning speed generally results in a thinner and denser membrane.…”

“…As a fast and cost-effective technique, slurry spin coating has been widely used to prepare gas-tight oxide electrolyte films. 18–20 Wang et al 21 fabricated a 10 μm-thick YSZ membrane on a NiO–YSZ anode support with slurry spin coating, and the maximum power density ( P max ) of the single cell reaches 2 W cm −2 at 800 °C. Chen et al 22 coated a 10 μm-thick anode functional layer (AFL) and a 5 μm-thick YSZ electrolyte membrane successively on a NiO–YSZ anode support, and the P max of the cell is 0.6 W cm −2 at 800 °C.…”