OXIDE ION TRANSPORT IN SOLID OXIDE FUEL CELLS

摘要

In a solid oxide fuel cell (SOFC) the electrolyte and partly also the composite electrodes are composed of oxide ion conducting materials. These materials are metal oxides, which usually have either fluorite or perovskite type of structure. The species to be transported is oxide ions. Several structural and thermodynamic parameters such as critical radius for the oxide along its pathway of movement, free lattice volume and average metal-oxide bond energy, have been proposed as predictors of high oxide ion conductivity. These parameters all depend on ionic radii, and therefore, some of these may be redundant. In this paper we explore the Interrelations among such parameters for fluorite and perovskite oxides by considering their sensitivities to the individual ionic radii. It is argued that lattice distortion (lattice stress and deviation from cubic symmetry) due to ion radii mismatch determines the ionic conductivity to a very large extent.