Adaptive kinetic Monte Carlo simulation of solid oxide fuel cell components

Ionic conductivities in the solid oxide fuel cell (SOFC) electrolytes yttria-stabilised zirconia (YSZ), calcia-stabilised zirconia (CSZ), gadolinium-doped ceria (GDC) and samarium-doped ceria (SDC) and the cathode material lanthanum strontium cobalt oxide (LSCO) are directly calculated using DL_AKMC, an adaptive kinetic Monte Carlo (aKMC) program which assumes limited a priori knowledge of the kinetics of systems. The materials were simulated over several milliseconds and over the range of experimentally most relevant temperatures and dopant concentrations (2-18 mol% for doped zirconia, 5-25 mol% for doped ceria and 5-80 mol% for LSCO). Ionic conductivities of the electrolytes at 1000 K are in good agreement with the observed values: CSZ in the range 3 x 10(-3) to 1 x 10(-2) S cm(-1) depending on dopant concentration, YSZ 4 x 10(-3) to 3 x 10(-2) S cm(-1), GDC 1 x 10(-2) to 5 x 10(-2) S cm(-1), SDC 1 x 10(-2) to 7 x 10(-2) S cm(-1). LSCO is predicted to have an ionic conductivity of the order of 10(-2) to 10(-1) S cm(-1) depending on Sr content. Average activation energies over all migration processes are 0.4-0.5 eV for the stabilised zirconias and 0.2-0.3 eV for the doped cerias and 0.3 eV for LSCO, in agreement with experiment. aKMC provides a distinct advantage over traditional KMC methods; in which one has to provide a list of system state transitions. Here, all of the state transitions are dynamically generated, leading to a more accurate simulation of the kinetics as the system evolves.