Electrical conductivity and TG-DSC study of hydration of Sc-doped CaSnO3 and CaZrO3

Correlations linking hydration thermodynamics to materials parameters can be of vital importance for further development of proton conducting oxides. However, the currently proposed correlations are troubled by scattering limiting their predictive power. As such, the present contribution has investigated Sc-doped CaSnO3 and CaZrO3 in an attempt to further elucidate the trends in the thermodynamics of hydration for perovskites. Conductivity and impedance spectroscopy on 5 and 10% Sc-doped CaSnO3 demonstrated that it is primarily an oxygen ion conductor with a small protonic contribution at lower temperatures (below 500 degrees C) under wet conditions. Simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC), TG-DSC, was applied to measure the standard molar hydration enthalpy of CaSn1-xScxO3-delta and CaZr1-xScxO3-delta (x = 0.05, 0.10, 0.15 and 020) as a function of the Sc concentration. The hydration enthalpy becomes increasingly negative with increasing Sc substitution, which is discussed on the basis of changes in electronegativity, basicity and tolerance factor. (C) 2014 Elsevier B.V. All rights reserved.