Doped and undoped TiO2 nanoparticles were prepared by St(o)ber method and thermally treated at 600 ℃.The effect of Nd3+ ion on the structure and microstructure of anatase-phase TiO2 nanocrystals was studied by Rietveld refinement method using X-ray powder diffraction data.Bond lengths,bond angles,and edges distances were analyzed.The phase formation was confirmed by high-resolution transmission electron microscopy.The adjustment of Ti-) bond length induced by the addition of Nd3+ ions,reduced the octahedral distortion and altered the octahedral array in the anatase-phase TiO2 nanocrystal.The changes of structure and microstructure were mainly observed for TiO2 nanoparticles doped with 0.1 at.％ of Nd3+ ions and attributed tothe cationic substitution of Ti4+ ions which promoted changes in the density of states and gap band of TiO2.The dopant insertion resulted in a better structural stability of the nanocrystals that enhanced their charge transference and photocatalytic efficiency.