The standard molar enthalpy of formation of SrY0.05Ce0.95O2.975 has been derived by combining the enthalpy of solution in 1 M HCl + 0.1 KI with auxiliary literature data, Delta H-f(o) (SrY0.05Ce0.95O2.925, s, 298.15 K) = -1720.4 +/- 3.4 kJ/mol. The formation enthalpy of SrY0.05Ce0.95O2.925 from the mixture of binary oxides is Delta H-ox(o) (298.15 K) = -45.9 +/- 3.4 kJ/mol and the enthalpy of reaction of SrY0.05Ce0.95O2.975 with water forming Sr(OH)(2), CeO2, and Y2O3 is Delta H-r(o) (298.15 K) = -85.5 +/- 3.4 kJ/mol. Our data and the entropies of different substances show that SrY0.05Ce0.95O2.975 is thermodynamically stable with respect to a mixture of SrO, Y2O3, CeO2 and that the reaction of SrY0.05Ce0.95O2.975 with water is thermodynamically favourable. (C) 2006 Elsevier B.V. All rights reserved.