Unusual properties of a model of an intergrain boundary in solid oxide ceramic electrolytes

A simple model of an intergrain region of an oxide ceramic electrolyte is used for kinetic Monte Carlo (KMC) simulations of the charge and electric field distribution in the system consisted of the grain bulks and intergrain region. The activation energies of thermally activated particle transitions in the grain bulk and intergrain region alongside the medium dielectric constant were the parameters of the model. The influence of the charge distribution on the grain boundary resistance is discussed. The density gradient contribution to the free energy was taken into account; the modified Nernst-Planck-Poisson (NPP) equation was formulated and used for the analysis of the charge distribution in the vicinity of the intergrain region. The analytical solutions of the modified NPP equation are compared with the results of the KMC simulations. The parameters of yttria stabilized zirconia are used as reference values while the model is of a more general nature.