Study on the Oxygen Diffusion Capacity of Black Zirconia by Molecular Dynamic Method

Abstract

Improving the oxygen diffusion capacity of solid electrolyte material is an important goal of researchers in recent decades. For this purpose, the blackening of zirconia was considered as a new strategy to enhance its oxygen diffusion capacity. We comparatively investigated the oxygen transport properties of white (YSZ, yttria stabilized zirconia) and black (ZSZ, Zr³⁺ stabilized zirconia) zirconia by molecular dynamics simulation. The simulation results show that the ZSZ has the same oxygen diffusion mechanism as YSZ. Furthermore, the ZSZ has a much better oxygen diffusion capacity than YSZ, which is confirmed by the lower minimum oxygen diffusion activation energy of ZSZ (0.37 eV) than that of YSZ (0.46 eV). The different oxygen diffusion capacity between YSZ and ZSZ is attributed to their crystal structure difference. The Zr³⁺ ionic radius is much closer to that of Zr⁴⁺ than that of Y³⁺, and it induces smaller lattice distortion in stabilized zirconia to impose a minimal steric blocking effect on the oxygen diffusion process. Therefore, the Zr³⁺ is preferred over Y³⁺to enhance the oxygen diffusion capacity of stabilized zirconia and the black YSZ co-doped by Y³⁺ and Zr³⁺ is proven to be a promising solid electrolyte material with a better oxygen diffusion capacity than YSZ.