Rietveld analysis of electron powder diffraction data from nanocrystallineanatase, TiO2

The structure of nanocrystalline anatase (TiO2) was successfully refined fr om electron powder diffraction data using the Rietveld technique. A polycry stalline sample (average crystal size about 70 Angstrom) was characterised by selected area electron diffraction in a conventional transmission electr on microscope operated at 300 kV. Radially integrated intensities were extr acted 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) Angstrom and c = 9.430(2) Angstrom. The reliability factors of the refi nement are R-wp = 5.2% and R-B = 2.6%. The close agreement of the refined s tructural parameters with previous results obtained from neutron diffractio n on coarse-grained powders proves the applicability of the method for char acterising nanocrystalline powders. The present study shows that Rietveld a nalysis on electron powder data is a good compliment to the existing method s for accurate structural investigations on nanocrystalline materials and t hin films. (C) 2000 Elsevier Science B.V. All rights reserved.