Large-area (001) oriented epitaxial CeO2 films with extremely high crystalline perfection characterized by x-ray diffraction rocking curves of the (002) CeO2 reflection with a full width at half maximum (FWHM) Δω≤0.013° and thickness dependent oscillations in the Bragg-Brentano x-ray diffraction spectra were deposited via rf-magnetron sputtering on (11_02) sapphire. Pole figure measurements of the space symmetry confirmed that the examined sharp reflections belong to CeO2 and no other phases like CeAlO3 are present. The improvement of the crystalline quality was obtained by optimization of the high-pressure sputter deposition process and the use of large-area substrates. The  CeO2 axis was slightly tilted with respect to the [11_02] sapphire axis by 0.185°. Subsequently sputter-deposited high-Tc YBa2Cu3O7-x thin films revealed structural properties characterized by FWHM ≪0.06° of the (005) θ-2θ peaks and by FWHM of the (005) peaks rocking curves of Δω=0.3°. © 1997 American Institute of Physics.