Large-area (001) oriented epitaxial CeO2films with extremely high crystalline perfection characterized by x-ray diffraction rocking curves of the (002) CeO2reflection with a full width at half maximum (FWHM)&Dgr;&ohgr;⩽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 toCeO2and no other phases like CeAlO3are 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 [100] CeO2axis was slightly tilted with respect to the [11_02] sapphire axis by 0.185°. Subsequently sputter-deposited high-TcYBa2Cu3O7−xthin films revealed structural properties characterized by FWHM<0.06°of the (005)&thgr;-2&thgr;peaks and by FWHM of the (005) peaks rocking curves of&Dgr;&ohgr;=0.3°.©1997 American Institute of Physics.