Cerium oxide films were deposited onto various yttria-stabilized zirconia (YSZ) electrolytes using supercritical fluid deposition (SFD) in a cold wall reactor. Deposition of ceria thin films (20-240 nm) was carried out via hydrolysis of a Ce precursor at 250-300 °C (typically 30 min) in supercritical CO₂ (scCO₂). The as-deposited films were continuous, dense and crystalline. They exhibited some carbon contamination which was eliminated in all cases by postannealing the films at 400 °C. Film microstructure depends on the hydrolysis conditions (water to cerium molar ratio), on the substrate nature (Si wafers or YSZ pellets) and on the YSZ pellet thickness (100 μm or 1 mm). Ceria films were then used as interlayers for intermediate temperature solid oxide fuel cells (IT-SOFC) between the YSZ electrolyte and the Nd₂NiO_4+δ cathode layer subsequently deposited. The electrochemical properties of the SOFC symmetrical half cells were investigated by electrochemical impedance spectroscopy (EIS). The presence of the undoped ceria layer deposited in scCO₂ lowers the resistance of the cell, compared both to cells with an optimized doped ceria layer deposited by screen printing and to cells without any interlayer.Read less <