Synthesis and Electron-Beam Evaporation of Gadolinium-Doped Ceria Thin Films

Gadolinium-doped ceria (GDC) nanopowders, prepared using the co-precipitation synthesis method, were applied as a starting material to form ceria-based thin films using the electron-beam technique. The scanning electron microscopy (SEM)analysis of the pressed ceramic pellets’ cross-sectional views showed a dense structure with no visible defects, pores, or cracks. The AC impedance spectroscopy showed an increase in the total ionic conductivity of the ceramic pellets with an increase in the concentration of Gd₂O₃ in GDC. The highest total ionic conductivity was obtained for Gd_0.1Ce_0.9O_2-δ (σ_total is 11 × 10⁻³ S·cm⁻¹ at 600^◦C), with activation energies of 0.85 and 0.67 eV in both the low-and high-temperature ranges, respectively. The results of the X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometer (ICP-OES) measurements revealed that the stoichiometry for the evaporated thin films differs, on average, by ~28% compared to the target material. The heat-treatment of the GDC thin films at 600^◦C, 700^◦C, 800^◦C, and 900^◦C for 1 h in the air had a minor effect on the surface roughness and the morphology. The results of Raman spectroscopy confirmed the improvement of the crystallinity for the corresponding thin films. The optimum heat-treating temperature for thin films does not exceed 800^◦C.