Issue 43, 2012

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

Abstract

In this contribution we investigate trends in the defect chemistry and hydration thermodynamics of rare-earth pyrochlore structured oxides, RE2X2O7 (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 RE2X2O7 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.

Graphical abstract: Hydration thermodynamics of pyrochlore structured oxides from TG and first principles calculations

Article information

Article type
Paper
Submitted
10 Jul 2012
Accepted
24 Aug 2012
First published
28 Aug 2012

Dalton Trans., 2012,41, 13343-13351

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

T. S. Bjørheim, V. Besikiotis and R. Haugsrud, Dalton Trans., 2012, 41, 13343 DOI: 10.1039/C2DT31517C

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