Reactions of cerium silicate formation in mechanically activated oxide powders of CeO2 and SiO2 (quarz) were studied. Three different mixtures were prepared, the compositions of which corresponded to Ce2Si2O7, Ce-4.67(SiO4)(3)O and Ce2SiO5. Oxide mixtures were mechanically activated in vibratory mill up to 120 min. X-ray analysis performed on activated mixtures showed that the CeO2 crystallite size decreased with increasing activation time. However, CeO2 lattice distortions passed through a maximum after 30 min of activation. The results obtained after heating showed that reactions proceeded via formation of intermediate compounds. Evidence of the existence of a liquid phase at 1550degreesC is given. (C) 2004 Kluwer Academic Publishers.