In order to determine the optimal dopant concentration in gadolinium-doped ceria, a systematic approach was used which involved a 3D kinetic lattice Monte Carlo model of vacancy diffusion in conjunction with previously calculated activation energies for vacancy migration in gadolinium-doped ceria, as inputs. kinetic lattice Monte Carlo simulations were performed including the vacancy repelling effects in gadolinium-doped ceria. Increasing the dopant concentration increases the vacancy concentration, which increases the ionic conductivity. However, at higher concentrations, vacancy-vacancy repulsion impedes vacancy diffusion, and together with vacancy trapping by dopants decreases the ionic conductivity. The maximum ionic conductivity was predicted to occur at ≈20 to 25% mole fraction of Gd dopant. Placing Gd dopants in pairs, instead of randomly, was found to decrease the conductivity by ≈50%. Overall, the trends in ionic conductivity results obtained using the kinetic lattice Monte Carlo model developed in this work were in reasonable agreement with the available experimental data. This kinetic lattice Monte Carlo model can be applied to a variety of ceria-based electrolyte materials for predicting the optimum dopant concentration.

Predicting the Optimal Dopant Concentration in Gadolinium Doped Ceria - a Kinetic Lattice Monte Carlo Approach. P.P.Dholabhai, S.Anwar, J.B.Adams, P.A.Crozier, R.Sharma: Modelling and Simulation in Materials Science and Engineering, 2012, 20[1], 015004