25 nm thick Gd-doped ceria thin films were grown on yttria-stabilized zirconia (YSZ) substrates with (110) and (111) orientation by pulsed laser deposition to study both their crystalline structure and interfacial stability. The films were characterized by high-energy grazing incidence x-ray diffraction, x-ray reflectivity and x-ray photoelectron spectroscopy before and after annealing to 1400 K under ultra-high vacuum (UHV) conditions. The films were found to be epitaxial to the YSZ substrates, exhibiting good crystalline quality without defects like twinning, and low surface roughness. Upon reduction due to the annealing in ultrahigh vacuum (UHV), both samples showed an increase in lattice parameter while maintaining their original crystalline quality. The x-ray reflectivity measurements gave evidence for interdiffusion after annealing by the presence of an additional interfacial layer with reduced electron density. X-ray photoelectron spectroscopy revealed an increase in the concentration of Ce3+ and also yttrium at the surface upon annealing, indicating a slight reduction of the surface as well as diffusion of yttrium to the surface. (C) 2016 The Authors. Published by Elsevier B.V.