A new method was presented for computing the electrical impedance of solid oxide electrolyte from kinetic Monte Carlo simulations of oxygen vacancy diffusion. The impedance values at all frequencies were obtained from a single equilibrium simulation based on the fluctuation–dissipation theorem, leading to a significant gain of efficiency over existing methods. This permitted the systematic examination of the effect of dopant concentration. Increasing the dopant concentration was found to decrease the infinite-frequency impedance, which was attributed to the increasing density of oxygen vacancies. The difference between the impedance values at zero- and infinite-frequency, on the other hand, exhibited the opposite trend, and was linked to dopant–vacancy interactions. Hence the two competing mechanisms, previously proposed to explain the existence of an optimal doping concentration, were separately quantified. The present model also predicted a significant effect of the arrangement of dopant cations upon the electrolyte conductivity.

Kinetic Monte Carlo Simulations of Oxygen Vacancy Diffusion in a Solid Electrolyte: Computing the Electrical Impedance using the Fluctuation–Dissipation Theorem. E.Lee, F.B.Prinz, W.Cai: Electrochemistry Communications, 2010, 12[2], 223-6