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Hydration thermodynamics of pyrochlore structured oxides from TG and first principles calculations.

Authors
  • Bjørheim, Tor S
  • Besikiotis, Vasileios
  • Haugsrud, Reidar
Type
Published Article
Journal
Dalton Transactions
Publisher
The Royal Society of Chemistry
Publication Date
Nov 21, 2012
Volume
41
Issue
43
Pages
13343–13351
Identifiers
DOI: 10.1039/c2dt31517c
PMID: 23001186
Source
Medline
License
Unknown

Abstract

In this contribution we investigate trends in the defect chemistry and hydration thermodynamics of rare-earth pyrochlore structured oxides, RE(2)X(2)O(7) (RE = La-Lu and X = Ti, Sn, Zr and Ce). First principles density functional theory (DFT) calculations have been performed to elucidate trends in the general defect chemistry and hydration enthalpy for the above-mentioned series. Further, to justify the use of such theoretical methods, the hydration properties of selected compositions were studied by means of thermogravimetric measurements. Both DFT calculations and TG measurements indicate that the hydration enthalpy becomes less exothermic with decreasing radii of RE ions within the RE(2)X(2)O(7) series (X = Ti, Sn, Zr and Ce), while it is less dependent on the X site ion. The observed hydration trends are discussed in connection with trends in the stability of both protons and oxygen vacancies and changes in the electronic density of states and bonding environment through the series. Finally, the findings are discussed with respect to existing correlations for other binary and ternary oxides.

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