Rietveld analysis of electron powder diffraction data from nanocrystalline anatase, TiO2

The structure of nanocrystalline anatase (TiO2) was successfully refined from electron powder diffraction data using the Rietveld technique. A polycrystalline sample (average crystal size about 70 A) was characterised by selected area electron diffraction in a conventional transmission electron microscope operated at 300 kV. Radially integrated intensities were extracted from digitised photographic films and used in the course of structure refinements by a standard program for Rietveld analysis. The structure was refined in space group I4(1)/amd (#141) with lattice parameters a = 3.7710(9) A and c = 9.430(2) A. The reliability factors of the refinement are Rwp = 5.2% and R(B) = 2.6%. The close agreement of the refined structural parameters with previous results obtained from neutron diffraction on coarse-grained powders proves the applicability of the method for characterising nanocrystalline powders. The present study shows that Rietveld analysis on electron powder data is a good compliment to the existing methods for accurate structural investigations on nanocrystalline materials and thin films.