PERCOLATION MODEL FOR THE ANOMALOUS CONDUCTIVITY OF FLUORITE-RELATED OXIDES

The Monte Carlo simulation technique has been used to study the anomal ous conductivity of aliovalently doped fluorite-related oxides. In ord er to investigate the effect of the interaction between the dopants an d the oxygen vacancies on the transport behavior, three simple model i nteractions have been tested: Nearest-neighbor attraction, nearest-nei ghbor repulsion, and a barrier model, which is based on the assumption of a reduced oxygen mobility in the neighborhood of the dopants. We f ind that percolation theory is essential to correlate the local intera ctions and the long-range mobility of the ions. Our numerical results show that satisfactory agreement with experiment can be obtained only for the barrier model.