Gadolinium-doped ceria offered the possibility of operation at 773 to 1073K. To determine the optimal dopant concentration in GDC, use was made of a systematic approach of applying a 3D kinetic lattice Monte Carlo model of vacancy diffusion in conjunction with previously calculated activation energies for vacancy migration in GDC as inputs. Kinetic lattice Monte Carlo simulations were performed including the vacancy repelling effects in GDC. Increasing the dopant concentration increased the vacancy concentration, which increased the ionic conductivity. However, at higher concentrations, vacancy-vacancy repulsion impedes vacancy diffusion, and together with vacancy trapping by dopants decreased 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 here were in reasonable agreement with the available experimental data. This kinetic lattice Monte Carlo model could 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