Doped Ceria for Solid Oxide Fuel Cells

Lower valent cation-doped CeO 2 materials have attracted remarkable research interest for the electrolyte application in solid oxide fuel cells operating in the intermediate temperature range (500–700°C). At these temperatures, the oxygen-ion conductivity of gad- olinium-doped ceria is about an order of magnitude higher than that of yttria-stabilized zirconia. The oxygen-ion diffusion in the cubic fluorite structure of CeO 2 is dependent on several factors such as charge valence and size of dopant cation, doping amount, etc. In the literature, several conductivity trends have been reported as a function of these parameters and are explained by the atomistic computational models. This chapter describes the highlights of the various activities that have been done in this regard to provide insights into the mechanisms underlying the oxygen-ion conduction process in acceptor-doped ceria. the concept of critical ionic radius alone cannot explain the maximum oxygen-ion conductivity observed in Pm 3+ -doped CeO 2 as found by the first-principles density functional theory calculations. Particular attention has been to a more recent atomistic simulations study on rare-earth-doped ceria which calculates the migration energies for all the possible jump configu rations that may present in rare-earth-doped CeO 2 . This study explains the importance of the shape of migration energy barrier and its impact on the ionic conductivity.