Hierarchical Percolation and Electrical Conduction of Glasses in the 50WO3-(50-x)P2O5-xNa2O system

The validity of the proposed concept of hierarchical percolation is demonstrated using glasses in the WO P2O5-Na2O system as an example. The dependence of the electrical conductivity sigma = sigma(0)(xi,xi(crit))(mu) (where xi the percolation parameter) with an exponent mu similar or equal to 1.4 close to the exponent theoretically predicted for two-dimensional percolation is obtained for the first time. This confirms our hypotheses regarding the two-dimensional percolation nature of electrical conduction over the surface of a phosphate cluster after the percolation threshold is overcome.