Optimized Sol–Gel Routes to Synthesize Yttria-Stabilized Zirconia Thin Films as Solid Electrolytes for Solid Oxide Fuel Cells

Sol–gel strategies are carefully evaluated and compared to synthesize electrolyte materials for Intermediate Temperature SOFCs (Solid Oxide Fuel Cells). Robust 10–20 μm thick cubic Yttria-Stabilized Zirconia (YSZ), (Y2O3)0.08(ZrO2)0.92, films have been prepared by using nanocomposite stable sols composed with "sol–gel made" YSZ binders and YSZ powder. Two different strategies have been investigated for the synthesis of 8YSZ binders: a mixed alkoxide-nitrate route in alcoholic media, and an environment-friendly hydrothermal route, in water media. Ionic conductivities of ∼2.5 × 10–2 S cm–1 are obtained at 800 °C for powders made by the hydrothermal and the alkoxide routes. Films synthesized from composite sols that contain commercial YSZ powder and the organic binder or the water-based binder, have been deposited on YSZ-NiO cermets and integrated in an entire single fuel cell. The two optimized routes yield to gastight YSZ electrolytes. In particular with the organic-based binder, a maximum power density of 250 mW cm–2 at 850 °C has been achieved. The proposed route can be extended to other materials for different applications such as ferroelectric and dielectric materials.