Abstract
The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO2-SiO2 and HfO2-SiO2 materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO2) x (SiO2)1 − x (M = Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750°C. Detailed observations for TiO2-SiO2 and ZrO2-SiO2 xerogels provide a basis for interpretation of new results for HfO2-SiO2 xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO2, but remain very finely mixed with silica network for ZrO2 and HfO2.
Similar content being viewed by others
References
P.C. Shultz and H.T. Smyth, in Amorphous Materials, edited by E.W. Douglas and B. Ellis (Wiley, London, 1972).
M. Nogami, J. Non-Cryst. Solids 69, 415 (1985).
M. Itoh, H. Hattori, and K.J. Tanabe, J. Catalysis 35, 225 (1974).
J.B. Miller and E.I. Ko, J. Catalysis 159, 58 (1996).
G.D. Wilk, R.M. Wallace, and J.M. Anthony, J. Appl. Physics 87, 484 (2000).
R. Gill, Chemical Fundamentals of Geology (Unwin Hyman, London, 1989).
R.J. Davis and Z. Liu, Chem. Mater. 9, 2311 (1997).
R. Anderson, G. Mountjoy, M.E. Smith, and R.J. Newport, J. Non-Cryst. Solids 232-234, 72 (1998).
G. Mountjoy, D.M. Pickup, G.W. Wallidge, J.M. Cole, R.J. Newport, and M.E. Smith, Chem. Phys. Lett. 304, 150 (1999).
S.W. Lee and R.A. Condrate, J. Mater. Sci. 23, 2951 (1988).
G. Mountjoy, R. Anderson, R.J. Newport, and M.E. Smith, J. Phys.: Cond. Matter 12, 3505 (2000).
D.M. Pickup, G. Mountjoy, G.W. Wallidge, R.J. Newport, and M.E. Smith, Phys. Chem. Chem. Phys. 1, 2527 (1999).
G. Mountjoy, D.M. Pickup, R. Anderson, G.W. Wallidge, M.A. Holland, R.J. Newport, and M.E. Smith, Phys. Chem. Chem. Phys. 2, 2455 (2000).
G. Mountjoy, J.S. Rigden, R. Anderson, G.W. Wallidge, R.J. Newport, and M.E. Smith, J. Mat. Res. 15, 1998 (2000).
G. Mountjoy, D.M. Pickup, M.A. Holland, R.J. Newport, G.W. Wallidge, and M.E. Smith, in Applications of Synchrotron Radiation Techniques to Materials Science V, edited by S.R. Stock, S.M. Mini, and D.L. Perry (MRS, Warrendale, 2000), p. 83.
N. Binsted, J.W. Campbell, S.J. Gurman, and P.C. Stephenson, CCLRC Daresbury Laboratory EXAFS Analysis Programs (1991).
L.A. Feigin and D.I. Svergun, Structure Analysis by Small-Angle X-Ray and Neutron Scattering (Plenum Press, New York, 1987).
Rights and permissions
About this article
Cite this article
Mountjoy, G., Holland, M., Gunawidjaja, P. et al. Comparing the Atomic Structures of Binary MO2-SiO2 (M = Ti, Zr or Hf) Xerogels. Journal of Sol-Gel Science and Technology 26, 161–164 (2003). https://doi.org/10.1023/A:1020774310142
Issue Date:
DOI: https://doi.org/10.1023/A:1020774310142