© 2018 Elsevier B.V. The interaction of CeO2nanoparticles with CF4gas at high temperature results in the formation of CeF3crystalline phase on the surface of nanoparticles. The lattice parameters of CeF3phase in CeO2/CeF3composite nanoparticles correspond to CeF3bulk. In the process of formation of CeF3crystalline phase, the Ce3+ions can occupy the various positions in crystal lattice: normal sites and perturbed sites arising due to location of O2−ions near to Ce3+ions. The energy transfer between Ce3+ions occupying normal and perturbed sites in CeF3phase has been observed.