Position preference and diffusion path of an oxygen ion in apatite-type lanthanum silicate La9.33Si6O26: A density functional study
Liao, T., Sasaki, T., Suehara, S., & Sun, Ziqi (2011) Position preference and diffusion path of an oxygen ion in apatite-type lanthanum silicate La9.33Si6O26: A density functional study. Journal of Materials Chemistry, 21(9), pp. 3234-3242.
Using density functional theory, we investigated the position preference and diffusion mechanisms of interstitial oxygen ions in lanthanum silicate La9.33Si6O26, which is an apatite-structured oxide and a promising candidate electrolyte material for solid oxide fuel cells. The reported lanthanum vacancies were explicitly taken into account by theoretically determining their arrangement with a supercell model. The most stable structures and the formation energies of oxygen interstitials were determined for each charged state. It was found that the double-negatively charged state is stable over a wide range of the Fermi level, and that the excess oxygen ions form split interstitials with the original oxygen ions, while the neutral and the single-negatively charged states preferably form molecular oxygen. These species were found near the lanthanum vacancy site. The theoretically determined migration pathway along the c-axis essentially follows an interstitialcy mechanism. The obtained migration barrier is sensitive to the charge state, and is also affected by the lanthanum vacancy. The barrier height of the double-negatively charged state was calculated to be 0.58 eV for the model structure, which is consistent with the measured activation energy.
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|Item Type:||Journal Article|
|Divisions:||Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Copyright Owner:||Copyright 2011 The Royal Society of Chemistry|
|Deposited On:||11 Apr 2016 22:33|
|Last Modified:||18 Apr 2016 04:48|
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