Structural investigations of nanomixed oxides SnO2-xAl2O3 prepared by sol-gel technique

Nanosize polycrystalline sample of the mixed oxides SnO2 + xAl(2)O(3)(x = 0, 25, 50, 75 wt%) were synthesized by sot-gel technique. The resulting samples were characterized with X-ray powder diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Rietveld quantitative phase analysis shows that part of alumina is incorporated into the SnO2 lattice while the other part remains as a separate phase. For the incorporated part, some Al3+ are accommodated substitutionally for Sn3+ and some is segregated on the grain boundary surface of SnO2. It is found that the grain size of the mixed oxides SnO2 + xAl(2)O(3) is below 10 nm while for pure SnO2 it is over 41 nm, indicating that alumina can effectively prevent SnO2 from further growing up in the process of calcination. This is confirmed by the big increase in the specific surface area for mixed oxide samples. (C) 2010 Elsevier B.V. All rights reserved.