Nanocrystalline solid solutions Ce0.8Nd0.2O2-delta with different grain size were synthesized by a sol-gel method. XRD measurements showed that the product obtained by sintering the fresh gel at 200 degreesC crystallized in a single fluorite structure and the grain size was calculated to be ca. 7.2 nm by Scherrer formula. The grain size for the solid solutions grew with the increase of sintering temperature. The first-order Raman spectra of the solid solutions exhibited two peaks. The strong band F(2)g mode at ca. 470 cm(-1) was assigned to the symmetric breathing mode of oxygen atoms around cerium ions, while the weak band at ca. 580 cm(-1) to the presence of oxygen vacancies. Accompanying with grain growth from 7.2 to 65.1 nm, the F-2g mode shifted ca. 9 cm(-1) towards higher frequencies, while the half-height width became narrower. The ionic conductivity for the solid solution Ce0.8Nd0.2O2-delta was sigma (500 degreesC) = 2 65 x 10(-3) S cm(-1), and the activation energy was 0.82 eV.