Abstract
The heat capacity and the enthalpy associated with the reported oxygen vacancy order-disorder transition in Ba2In2O5 were measured by high temperature step scanning calorimetry. The transition temperature is 1205 ± 2 K. The transition appears first order or nearly so. The enthalpy and entropy of transition are 1.3 kJ/mol and 1.1 J/mol K, respectively. The latter is only 4.8% of the configurational entropy, arising from mixing one vacancy and five oxygens per formula unit, 22.5 J/mol K. This suggests that the transition involves only a small fraction of the oxygen vacancies and implies extensive short-range order, SRO, in the high temperature phase.
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Prasanna, T.R.S., Navrotsky, A. Energetics of the oxygen vacancy order-disorder transition in Ba2In2O5. Journal of Materials Research 8, 1484–1486 (1993). https://doi.org/10.1557/JMR.1993.1484
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DOI: https://doi.org/10.1557/JMR.1993.1484