Understanding oxide ion transport in cation-ordered yttria-stabilized zirconia

Abstract

Classical molecular dynamics simulations are carried out on cationically ordered yttria-doped zirconia, Y_xZr_1−xO_2−x/2, at the dopant (Y³⁺) concentration of x = 12.5%. A variety of Zr⁴⁺/Y³⁺ ordered structures are examined for local migration pathways and microscopic energetics governing oxide ion transport in the system. Starting from a layer of cubic Y₂O₃ spanning the basal plane, the number of Y³⁺ layers in the simulation cell is multiplied systematically, at the expense of their coverage per layer. The study reveals that cationic ordering in Y_xZr_1−xO_2−x/2 can produce a profound impact on the oxide ion transport in the framework, wherein with the maximal dispersion of the dopant a four-fold enhancement in the ionic conductivity is observed relative to the cationically disordered matrix. We demonstrate that this improvement in ion mobility is due to the homogenization of oxide ion vacancies across the matrix. This study thus provides valuable insights for the enhancement of the electrochemical performance of solid oxide fuel cells.