Extreme temperature gradient promoting oxygen diffusion in yttria-stabilized zirconia: A molecular dynamics study

The oxidation resistance of yttria-stabilized zirconia (YSZ) thermal barrier coatings and conductivity of YSZ solid oxide fuel cells are closely related to the diffusion of oxygen ions (O2-$\text{O}<^>{2-}$) in YSZ, but the O2-$\text{O}<^>{2-}$ diffusion behavior in small-sized YSZ samples under non-isothermal condition where the temperature gradient (del T$\nabla T$) could be significant remaining elusive. Herein, we disclose the previously unrevealed effect of extreme del T$\nabla T$ on the self-diffusion behavior of O2-$\text{O}<^>{2-}$ in both pristine and strained YSZ. It is found that the O2-$\text{O}<^>{2-}$ self-diffusion coefficient (D$D$) experiences a nearly one-fold increase under an extreme del T$\nabla T$ around 60 K/& Aring;. The diffusion direction tends to be toward regions of high temperature. Uniaxial stress is revealed to reduce D$D$ due to the increased activation energy of ions, whereas del T$\nabla T$ promotes the O2-${\text{O}}<^>{2-}$ self-diffusion in the stressed system. These results underscore the role of del T$\nabla T$ in influencing the self-diffusion behavior of YSZ, providing a theoretical guideline for examining ceramics serving in extreme environments. Extreme temperature gradient promotes O2- self-diffusion in yttria-stabilized zirconia, with a diffusion direction towards regions of high temperature. Our work provides a theoretical guideline for examining diffusion in ceramics exposed to extreme environments. image