The elastic modulus of fluorite-structured pure ceria, Gd-doped ceria and yttria-stabilized zirconia, having differing O-vacancy concentrations, were measured by using the nano-indentation technique. The samples were heat-treated (800C, 15h), under O partial pressures ranging from 0.21 to 10−25atm, until equilibrium was reached at a sufficient depth. The defect concentrations were conserved by fast cooling to room temperature. The results revealed that the elastic modulus of both pure ceria and of Gd-doped ceria decreased drastically in samples which were heat-treated under very low O partial pressures. However, the elastic modulus change for yttria-stabilized zirconia was insignificant. Analysis of the experimental results suggested that an increase in the point defect content weakened the attractive forces between atoms in fluorite-structured oxides.

The Effect of Oxygen Vacancy Concentration on the Elastic Modulus of Fluorite-Structured Oxides. Y.Wang, K.Duncan, E.D.Wachsman, F.Ebrahimi: Solid State Ionics, 178[1-2], 53-8