Electrical conductivity of Gd-doped ceria film fabricated by aerosol deposition method

Gd-doped ceria (GDC) films were deposited on various substrates using aerosol deposition (AD) method in order to determine whether this process is useful for the fabrication of thin (~ 1 μm) electrolyte layers. The AD method is attractive because no vacuum equipment or target material is required. Although the AD method utilizes pre-calcined powder for the deposition of film, the particle size and microstructure of films are largely dependent upon the choice of substrate (sapphire, glass, Si–Pt). The film deposited on sapphire substrate had a relatively dense microstructure and the smallest particle size. Total conductivity of film was measured using either in-plane or across-plane mode depending upon the substrate. Across-plane measurement gave a lower conductivity than in-plane measurement, possibly due to the difficulty of current collection or anisotropic microstructure. The magnitude of in-plane conductivity was comparable to the conductivity of a bulk sample, i.e., ~ 1.2 × 10− 3 S/cm at 450 °C for the film deposited on sapphire. The activation energy of electronic conductivity at 300–450 °C was also similar, ~ 2.23 eV. However, the activation energy of ionic conductivity differed depending upon the substrates: ~ 0.71 eV for the film on sapphire substrate and 0.93–0.94 eV for other films. The Po2 dependence had a − 1/4 slope, similar to that of bulk or film form of GDC at higher (> 500 °C) temperature. Overall, the AD method may be useful for the deposition of thin-film GDC since the conductivity was similar with that of film or bulk samples fabricated by conventional methods.