Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Cooperative mechanisms of fast-ion conduction in gallium-based oxides with tetrahedral moieties


The need for greater energy efficiency has garnered increasing support for the use of fuel-cell technology, a prime example being the solid-oxide fuel cell1,2. A crucial requirement for such devices is a good ionic (O2− or H+) conductor as the electrolyte3,4. Traditionally, fluorite- and perovskite-type oxides have been targeted3,4,5,6, although there is growing interest in alternative structure types for intermediate-temperature (400–700 C) solid-oxide fuel cells. In particular, structures containing tetrahedral moieties, such as La1−xCaxMO4−x/2(M=Ta,Nb,P) (refs 7,8), La1−xBa1+xGaO4−x/2 (refs 9,10) and La9.33+xSi6O26+3x/2 (ref. 11), have been attracting considerable attention recently. However, an atomic-scale understanding of the conduction mechanisms in these systems is still lacking; such mechanistic detail is important for developing strategies for optimizing the conductivity, as well as identifying next-generation materials. In this context, we report a combined experimental and computational modelling study of the La1−xBa1+xGaO4−x/2 system, which exhibits both proton and oxide-ion conduction9,10. Here we show that oxide-ion conduction proceeds via a cooperative ‘cog-wheel’-type process involving the breaking and re-forming of Ga2O7 units, whereas the rate-limiting step for proton conduction is intra-tetrahedron proton transfer. Both mechanisms are unusual for ceramic oxide materials, and similar cooperative processes may be important in related systems containing tetrahedral moieties.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Crystal structure of LaBaGaO4.
Figure 2: Local structure around an oxide-ion vacancy defect in the LaBaGaO4 system.
Figure 3: Lowest-energy pathway for oxygen vacancy migration in La1−xBa1+xGaO4−x/2.
Figure 4: Molecular dynamics simulation trajectories of oxide ions in three mutually perpendicular planes.
Figure 5: Proton configuration and migration in LaBaGaO4.

Similar content being viewed by others


  1. Steele, B. C. H. & Heinzel, A. Materials for fuel-cell technologies. Nature 414, 345–352 (2001).

    Article  CAS  Google Scholar 

  2. Atkinson, A. et al. Advanced anodes for high-temperature fuel cells. Nature Mater. 3, 17–27 (2004).

    Article  CAS  Google Scholar 

  3. Goodenough, J. B. Oxide-ion electrolytes. Annu. Rev. Mater. Res. 33, 9 (2003).

    Article  Google Scholar 

  4. Norby, T. & Larring, Y. Concentration and transport of protons in oxides. Curr. Opin. Solid State Mater. Sci. 2, 593–599 (1997).

    Article  CAS  Google Scholar 

  5. Kreuer, K. D. Proton-conducting oxides. Annu. Rev. Mater. Res. 33, 333–359 (2003).

    Article  CAS  Google Scholar 

  6. Iwahara, H. Proton conducting ceramics and their applications. Solid State Ion. 86–88, 9–15 (1996).

    Article  Google Scholar 

  7. Haugsrud, R. & Norby, T. Proton conduction in rare-earth ortho-niobates and ortho-tantalates. Nature Mater. 5, 193–196 (2006).

    Article  CAS  Google Scholar 

  8. Kitamura, N., Amezawa, K. & Tomii, Y. Electrical conduction properties of Sr-doped LaPO4 and CePO4 under oxidizing and reducing conditions. J. Electrochem. Soc. 152, A658–A663 (2005).

    Article  CAS  Google Scholar 

  9. Li, S., Schönberger, F. & Slater, P. La1−xBa1+xGaO4−x/2: a novel high temperature proton conductor. Chem. Comm. 21, 2694–2695 (2003).

    Article  Google Scholar 

  10. Schönberger, F., Kendrick, E., Islam, M. S. & Slater, P. Investigation of proton conduction in La1−xBa1+xGaO4−x/2 and La1−xSr2+xGaO5−x/2 . Solid State Ion. 176, 2951–2953 (2005).

    Article  Google Scholar 

  11. Kendrick, E., Islam, M. S. & Slater, P. R. Developing apatites for solid oxide fuel cells: Insight into structural, transport and doping properties. J. Mater. Chem. 17, 3104–3111 (2007).

    Article  CAS  Google Scholar 

  12. Kilner, J. A. Optimisation of oxygen ion transport in materials for ceramic membrane devices. Faraday Discuss. 134, 9–15 (2007).

    Article  CAS  Google Scholar 

  13. Haile, S. M., Boysen, D. A., Chisholm, C. R. I. & Merle, R. B. Solid acids as fuel cell electrolytes. Nature 410, 910–913 (2001).

    Article  CAS  Google Scholar 

  14. Larson, A. C. & Von Dreele, R. B. “General Structure Analysis System (GSAS)”, Los Alamos National Laboratory Report LAUR 86–748 (1994) Toby, B. H. EXPGUI, a graphical user interface for GSAS. J. Appl. Cryst. 34, 210–213 (2001).

    Article  Google Scholar 

  15. Gale, J. D. & Rohl, A. L. The general utility lattice program. Mol. Simul. 29, 291–341 (2003).

    Article  CAS  Google Scholar 

  16. Catlow, C. R. A. (ed.) Computer Modelling in Inorganic Crystallography (Academic, San Diego, 1997).

  17. Refson, K. Moldy: a portable molecular dynamics simulation program for serial and parallel computers. Comput. Phys. Commun. 126, 309–328 (2000).

    Article  Google Scholar 

  18. Baroni, S. et al. <>.

  19. Vanderbilt, D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. Phys. Rev. B 41, 7892–7895 (1990).

    Article  CAS  Google Scholar 

  20. Burke, K., Perdew, J. P. & Wang, Y. in Electronic Density Functional Theory: Recent Progress and New Directions (eds Dobson, J. F., Vignale, G. & Das, M. P.) (Plenum, New York, 1998).

    Google Scholar 

  21. Perdew, J. P. et al. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46, 6671–6687 (1992).

    Article  CAS  Google Scholar 

  22. Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13, 5188–5192 (1976).

    Article  Google Scholar 

  23. Islam, M. S. Ionic transport in ABO3 perovskite oxides: a computer modelling tour. J. Mater. Chem. 10, 1027–1038 (2000).

    Article  CAS  Google Scholar 

  24. Minervini, L., Grimes, R. W. & Sickafus, K. E. Disorder in pyrochlore oxides. J. Am. Ceram. Soc. 83, 1873–1878 (2000).

    Article  CAS  Google Scholar 

  25. Sayle, T. X. T., Parker, S. C. & Sayle, D. C. Oxygen transport in unreduced, reduced and Rh(III)-doped CeO2 crystals. Faraday Discuss. 134, 377–397 (2007).

    Article  CAS  Google Scholar 

Download references


This work was supported by the EPSRC (Project grant: GR/S55507/02). We would also like to thank ISIS, Rutherford Appleton Laboratory UK for access to neutron diffraction facilities.

Author information

Authors and Affiliations


Corresponding authors

Correspondence to M. Saiful Islam or Peter R. Slater.

Supplementary information

Supplementary Information

Supplementary tables 1-2 and figures 1-6 (PDF 1489 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kendrick, E., Kendrick, J., Knight, K. et al. Cooperative mechanisms of fast-ion conduction in gallium-based oxides with tetrahedral moieties. Nature Mater 6, 871–875 (2007).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing