The strain effect on colossal oxygen ionic conductivity in nanoscale zirconia electrolytes: A first-principles-based study

Density functional theory calculations and first-principles molecular dynamics (MD) simulations have been performed to examine the strain effect on the colossal oxygen ionic conductivity in selected sandwich structures of zirconia electrolytes. For the KTaO₃/YSZ/KTaO₃ sandwich structure with 9.7% lattice mismatch, transition state calculations indicate that the strain effect changes the oxygen migration pathways from straight line into zigzag form and reduces the energy barrier by 0.2 eV. On the basis of our computational results, a possible oxygen ion diffusion highway is suggested. By finite-temperature MD simulations, an activation barrier of 0.33 eV is obtained, corresponding to an oxygen ionic conductivity which is 6.4 × 10 ⁷ times higher than that of the unstrained bulk zirconia at 500 K. A nearly linear relationship is identified between the energy barrier and the lattice mismatch in the sandwich structures.