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Journal of Solid State Electrochemistry

, Volume 8, Issue 9, pp 668–673 | Cite as

Effect of Ba and Bi doping on the synthesis and sintering of Ge-based apatite phases

  • J. R. Tolchard
  • J. E. H. Sansom
  • P. R. SlaterEmail author
  • M. S. Islam
Original Paper

Abstract

Recently, high oxide ion conduction has been observed in the apatite-type systems La9.33+x(Si/Ge)6O26+x/2, with conductivities approaching and even exceeding that of yttria-stabilized zirconia. The Ge-based phases have been reported to suffer from Ge loss and undergo irreversible structural changes on sintering at the high temperatures required to obtain dense pellets. In this paper we discuss doping studies (Ba, Bi for La) aimed at stabilizing the hexagonal apatite lattice to high temperature, and/or lowering the synthesis and sintering temperatures. The results show that doping with Ba helps to stabilize the hexagonal lattice at high temperatures, although Ge loss appears to still be a problem. Conductivity data show that, as previously reported for the Si-based systems, non-stoichiometry in the form of cation vacancies and/or oxygen excess is required to achieve high oxide ion conduction in these Ge-based systems. Neutron diffraction structural data for the fully stoichiometric phase La8Ba2Ge6O26 shows that the channel oxygen atoms show little anisotropy in their thermal displacement parameters, consistent with the low oxide ion conductivity of this phase. Bi doping is shown to lower the synthesis and sintering temperatures, although the presence of Bi means that these samples are not stable at high temperatures under reducing conditions.

Keywords

Apatite Germanium Oxide ion conduction Solid oxide fuel cells 

Notes

Acknowledgements

We would like to thank EPSRC and Merck Ltd for funding. We would also like to thank ISIS, Rutherford Appleton Laboratory, for the provision of neutron diffraction facilities, and R. Smith for help with the collection of neutron powder diffraction data.

References

  1. 1.
    Nakayama S, Aono H, Sadaoka Y (1995) Chem Lett 431Google Scholar
  2. 2.
    Nakayama S, Sakamoto M (1998) J Eur Ceram Soc 18:1413CrossRefGoogle Scholar
  3. 3.
    Nakayama S, Sakamoto M, Higuchi M, Kodaira K, Sato M, Kakita S, Suzuki T, Itoh K (1999) J Eur Ceram Soc 19:507CrossRefGoogle Scholar
  4. 4.
    Tao S, Irvine JTS (2001) Mater Res Bull 36:1245CrossRefGoogle Scholar
  5. 5.
    Sansom JEH, Richings D, Slater PR (2001) Solid State Ionics 139:205CrossRefGoogle Scholar
  6. 6.
    Abram EJ, Sinclair DC, West AR (2001) J Mater Chem 11:1978CrossRefGoogle Scholar
  7. 7.
    Arikawa H, Nishiguchi H, Ishihara T, Takita Y (2000) Solid State Ionics 136–137:31Google Scholar
  8. 8.
    Ishihara T, Arikawa H, Akbay T, Nishiguchi H, Takita Y (2001) J Am Chem Soc 123:203CrossRefPubMedGoogle Scholar
  9. 9.
    McFarlane J, Barth S, Swaffer M, Sansom JEH, Slater PR (2002) Ionics 8:149Google Scholar
  10. 10.
    Sansom JEH, Hildebrandt L, Slater PR (2002) Ionics 8:155Google Scholar
  11. 11.
    Slater PR, Sansom JEH (2003) Solid State Phenom 90–91:195Google Scholar
  12. 12.
    Nakayama S, Sakamoto M (2001) J Mater Sci Lett 20:1627CrossRefGoogle Scholar
  13. 13.
    Berastegui P, Hull S, Garcia Garcia FJ, Grins J (2002) J Solid State Chem 168:294CrossRefGoogle Scholar
  14. 14.
    Islam MS, Tolchard JR, Slater JR (2003) Chem Commun 1486Google Scholar
  15. 15.
    Tolchard JR, Islam MS, Slater PR (2003) J Mater Chem 13:1956CrossRefGoogle Scholar
  16. 16.
    Sansom JEH, Tolchard JR, Slater PR, Islam MS (2004) Solid State Ionics (in press)Google Scholar
  17. 17.
    Sansom JEH, Slater PR (2004) Solid State Ionics (in press)Google Scholar
  18. 18.
    Larson AC, Von Dreele RB (1987) Los Alamos National Laboratory, report no LA-UR-86-748Google Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • J. R. Tolchard
    • 1
  • J. E. H. Sansom
    • 1
  • P. R. Slater
    • 1
    Email author
  • M. S. Islam
    • 1
  1. 1.Department of ChemistryUniversity of SurreyGuildfordUK

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