A composite sol–gel process to prepare a YSZ electrolyte for Solid Oxide Fuel Cells

► We synthesize and characterize a new YSZ composite sol with a low organic content using the sol–gel process. ► We deposit this composite sol on sintered or non-sintered YSZ–NiO cermet to prepare a dense electrolyte with the dip-coating technique. ► We study the influence of the composite sol composition, the support, the sintering temperature, co-sintering on the film microstructure. ► The dense electrolyte is processed in an entire fuel cell. ► We characterize the electrical performances of the as prepared dense electrolyte in an entire fuel cell. ZrO2–8% Y2O3 (YSZ) thick film was deposited on a YSZ–NiO anode and co-sintered to obtain a gas-tight electrolyte for an application as Solid Oxide Fuel Cell. A YSZ sol–gel composite sol is synthesized from a YSZ colloidal binder and a YSZ commercial powder and deposited as a thick (>10μm) monolayer by the dip-coating process. The evolution of the composite sol viscosity with time and its influence on the deposited film thickness is studied. The influence of the composite sol composition, the film sintering on the films microstructure is also studied in order to achieve dense films. The interest of co-sintering the electrolyte with the anodic support is demonstrated. Ionic conductivity and activation energy are measured on pellets obtained from pressed-powder obtained from (a) the calcination of composite sol and (b) the commercial powder. Conductivity of 0.03Scm−1 at 800°C and activation energy of 0.9eV were measured through impedance spectroscopy. Finally, an entire cell is processed with the developed electrolyte and polarization curves (I–V) were measured at 850°C. OCV of 1.23V was achieved, indicating the quality of the synthesized YSZ electrolyte.