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Protonic defects and water incorporation in Si and Ge-based apatite ionic conductors

Panchmatia, P. M. and Orera, A. and Kendrick, E. and Hanna, John V. and Smith, Mark E. and Slater, P. R. and Islam, M. S. (2010) Protonic defects and water incorporation in Si and Ge-based apatite ionic conductors. Journal of Materials Chemistry, 20 (14). pp. 2766-2772.

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Abstract

Apatite-type oxide-ion conductors have attracted considerable interest as potential fuel cell electrolytes. Atomistic modelling techniques have been used to investigate oxygen interstitial sites, protonic defects and water incorporation in three silicate and three germanate-based apatite-systems, namely La8Ba2(SiO4)(6)O-2, La-9.33(SiO4)(6)O-2, La-9.67(SiO4)(6)O-2.5, La8Ba2(GeO4)(6)O-2, La-9.33(GeO4)(6)O-2, and La-9.67(GeO4)(6)O-2.5. The simulation models reproduce the complex experimental structures for all of these systems. The interstitial defect simulations have examined the lowest energy configuration and confirm this site to be near the Si?GeO4 tetrahedra. The water incorporation calculations identify the O-H protonic site to be along the O-4 oxygen channel as seen in naturally occurring hydroxy-apatites. The results also show more favourable and exothermic water incorporation energies for the germanate based apatites. This is consistent with recent experimental work, which shows that Ge-apatites take up water more readily than the silicate analogues.

Item Type: Article
Journal or Publication Title: Journal of Materials Chemistry
Subjects:
Departments: VC's Office
ID Code: 52818
Deposited By: ep_importer_pure
Deposited On: 28 Feb 2012 11:06
Refereed?: Yes
Published?: Published
Last Modified: 09 Apr 2014 23:09
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/52818

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