Determination of the enthalpy of hydration of oxygen vacancies in Y-doped BaZrO3 and BaCeo3 by TG-DSC

Simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC), TG-DSC, have been applied for the first time to measure directly the standard molar enthalpy changes of a defect chemical reaction, here the hydration of oxygen vacancies in two proton conducting perovskite oxides, BaCe0.9Y0.1O3-delta (BZY10) and BaCe0.9Y0.1O3-delta (BCY10). The measurements were done isothermally by parallel recording of the weight and heat exchanges associated with step changes in the water vapour pressure. The obtained molar hydration enthalpy of BZY10 was investigated at 300-900 degrees C and was found constant at -81 +/- 4 kJ mol(-1) (per mole of H2O) over this range. The molar hydration enthalpy of BCY10 was investigated at 600 degrees C and found to be -170 +/- 6 kJ mol(-1). Both values are in good agreement with the majority of literature data for the two materials obtained more indirectly by equilibrium methods. (C) 2010 Elsevier B.V. All rights reserved.