Diffusion and conductivity properties of cerium niobate

The tracer diffusion coefficient (D⁎) and the surface exchange coefficient (k⁎) provide vital information for materials used in high temperature electrochemical devices (e.g. solid oxide fuel cells or oxygen permeation membranes). These values were established for the high temperature tetragonal scheelite structured CeNbO4+δ (monoclinic fergusonite at room temperature), which is of interest due to its wide range of oxygen stoichiometries varying from stoichiometric CeNbO4 to CeNbO4.33. Measurements of D⁎ and k⁎ were performed by the isotopic exchange/line scan technique with SIMS (secondary ion mass spectrometry) used to determine 18O stable isotope depth distribution. This process was carried out between temperatures of 1073 K and 1173 K at 500 mbar of 16O/18O. These measurements were then correlated with oxide ion conductivity data previously determined from four probe d.c. and e.m.f. measurements using the Nernst–Einstein relation.