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Development of apatite-type oxide ion conductors
P R Slater1, J E H Sansom, J R Tolchard
1Materials Chemistry Group, Chemistry, SBMS, University of Surrey, Guildford, GU2 7XH, Surrey, UK. p.slater@surrey.ac.uk
Chemical Record (New York, N.Y.)
|March 2, 2005
Summary
Apatite-type oxide ion conductors show promise for Solid Oxide Fuel Cells. Optimized materials with excess oxygen exhibit high conductivity via interstitial ions, not vacancies.
Area of Science:
- Materials Science
- Electrochemistry
- Solid State Chemistry
Background:
- Oxide ion conductivity is crucial for Solid Oxide Fuel Cells (SOFCs).
- Apatite-type structures offer flexibility for cation substitution.
- Understanding conduction mechanisms is key for material development.
Purpose of the Study:
- To review recent advancements in apatite-type oxide ion conductors.
- To explore the relationship between structure, doping, and conductivity.
- To identify pathways for enhancing ionic conductivity in these materials.
Main Methods:
- Review of existing literature on apatite-type oxide ion conductors.
- Analysis of conductivity studies on doped apatite samples.
- Investigation of non-stoichiometry and its effect on ionic transport.
Main Results:
- Apatite structure allows extensive cation substitution.
- High oxide ion conduction requires non-stoichiometry (cation vacancies or oxygen excess).
- Oxygen excess yields the highest conductivities.
- Conduction mechanism appears to involve interstitial oxide ions, differing from perovskites/fluorites.
Conclusions:
- Apatite-type electrolytes are potential candidates for fuel cell applications.
- Further optimization, especially in Ge-containing systems, can significantly improve conductivity.
- The interstitial ion conduction mechanism offers a new avenue for designing efficient oxide ion conductors.