Elastic properties of ceramic oxides used in solid oxide fuel cells (SOFC)

Measurements are presented for the effective Young's (E*) and shear (G*) moduli and Poisson's ratio of some materials of interest for solid oxide fuel cells (SOFC), namely 10 and 20 mol% Gd2O3 doped CeO2 (GCO), 3 and 8 mol% Y2O3 stabilized ZrO2 (TZP and YSZ), and 75 mol% NiO-YSZ. The dependence of moduli on porosity was characterized by employing both theoretical (composite sphere method, CSM) and empirical (exponential, nonlinear, and linear) equations. The theoretical and empirical equations were tested by determining the goodness of fit of the equations to the experimental data and the standard error of estimation. All the equations described the modulus-porosity relationships equally well, except that, for NiO-YSZ, the empirical equations yield better fits than the CSM equations. This was attributed to the fact that the CSM equations, derived for two-phase composites, might not hold for calculating the effective moduli of three-phase composites, such as these NiO-YSZ materials. (C) 1997 Elsevier Science Limited.