Surface Diffusion of Oxygen Transport Membrane Materials Studied by Grain‐Boundary Grooving

Abstract

Mass transport mechanism responsible for grain‐boundary grooving during thermal annealing of polished ceramics of Ba0.5Sr0.5Co0.8Fe0.2O3‐δ (BSCF) and La2NiO4+δ (LN) was revealed by atomic force microscopy. Surface diffusion mechanism was confirmed for both materials by the evolution of the grain‐boundary width (w) with annealing time (t), and the surface diffusion coefficient was determined from the slope of w versus t1/4 following the theory by Mullins. An Arrhenius temperature dependence of the surface diffusion was observed, and the activation energy was determined to be 220 ± 30 and 450 ± 30 kJ/mol, respectively, for BSCF and LN. The surface diffusion data are discussed with respect to similar data for other oxide materials and cation and oxygen anion diffusion in BSCF and LN. Finally, the dihedral angle for both LN and BSCF was determined, and these are typical in the range reported for other oxide materials.