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Energetics in the brownmillerite-perovskite pseudobinary Ca2Fe2O5-CaTiO3

Published online by Cambridge University Press:  03 March 2011

T.R.S. Prasanna  and
A. Navrotsky
T.R.S. Prasanna
Affiliation:
Department of Geological and Geophysical Sciences and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544-1003
A. Navrotsky
Affiliation:
Department of Geological and Geophysical Sciences and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544-1003
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Abstract

The energetics of intermediate phases in the Ca2Fe2O5-CaTiO3 pseudobinary system was determined by high temperature solution calorimetry. The results suggest that both the intermediate compounds Ca3Fe2TiO8 and Ca4Fe2Ti2O11 are entropically stabilized because their enthalpies of formation are positive with respect to a mixture of Ca2Fe2O5 and CaTiO3. At high temperatures, the configurational entropy of the random distribution of Fe and Ti ions on the octahedral sites appears sufficient to stabilize the intermediate phases. The enthalpies of formation from the oxides at 1073 K of Ca2Fe2O5, Ca3Fe2TiO8, and Ca4Fe2Ti2O11 are −45.0 ± 3.8, −123.7 ± 8.0, and −192.7 ± 11.2 kJ/mol, respectively. Their enthalpies of formation from the elements at 298 K are −2139.8 ± 4.4, −3798.4 ± 8.6, and −5447.3 ± 12.2 kJ/mol, respectively.

Type
Articles
Information
Journal of Materials Research , Volume 9 , Issue 12 , December 1994 , pp. 3121 - 3124
Copyright
Copyright © Materials Research Society 1994

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References

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