Atomistic simulations of anisotropic mechanical behavior in non-stoichiometric gadolinia-doped ceria solid electrolytes

Gadolinia-doped ceria (GDC), as an electrolyte of solid oxide fuel cells, reduces its mechanical property when exposed to reducing conditions. In this paper, the anisotropic mechanical behavior of non-stoichiometric GDC solid electrolytes is investigated by using the molecular dynamics (MD) method. It is found that the oxygen vacancies whether from doping Gd3+ ions or generating Ce3+ ions by reduction have a serious impact on the mechanical properties such as phase transformation and fracture strength. The defect-dependent tensile strength is observed to be consistent with reported experimental measurements. Moreover, increasing temperature reduces the fracture strength. The influence of temperature on the critical nucleation stress and the fluorite phase strength is further analyzed. Beyond that, GDC undergoes volumetric expansion due to non-stoichiometric effects. The linear chemical strain and coefficient of compositional expansion (CCE) are calculated and compared with the experimental results.