MC-STUDY OF THE ANOMALOUS CONDUCTIVITY OF FLUORITE-TYPE SOLID OXIDE SOLUTIONS

The composition dependence of the conductivity of fluorite-related oxi des (XOr)(x) (MO2)(1-x) (r = 1 for divalent and r = 3/2 for trivalent dopants X; M = Zr, Ce, Th) has been studied by Monte Carlo simulations . Three simple model potentials have been tested in order to investiga te the dopant-vacancy interaction effects on the transport behaviour: nearest neighbour attraction, nearest neighbour repulsion and a barrie r-type model potential based on the assumption of a reduced oxygen mob ility in the neighbourhood of the dopants. Satisfactory agreement with experiment can be achieved only within the last approach. As shown by the numerical results, percolation theory is essential to relate the local interactions and the long range mobility of the oxygen ions.