The dc electrical conductivity, σdc, was measured at room temperature by using the ac impedance method for (AgI)x–(Ag2O)y–(B2O3)1-(x+y) (x = 0.75–0.85;y = 0.09–0.15) glasses, which were prepared by using the twin-roller rapid quenching method. X-ray and scanning electron microscope analyses showed that, together with β-AgI crystallites with poor σdc, nanocrystallites of α-AgI with high σdc were dispersed in the glass matrix with low σdc. The volume fraction of α-AgI phase, V1, was determined successfully from the measured 109Ag NMR spectrum and the density. The value of σdc increased with the increase of V1. The behavior of σdc was analyzed based on the generalized effective medium theory for the coexisting system of three phases. A supplementary analysis was performed based on a power law in the percolation theory. A threshold value of 0.144 was obtained for the ionic conduction, Vc. The values of the critical exponents were deduced to be 1.98 and 0.86, respectively. These characteristic values of percolation were in good agreement with the universal values, which were predicted by computer simulations for the percolation of electrical conduction.

The Evolution of the Ionic Conduction of (AgI)x–(Ag2O)y–(B2O3)1-(x+y) Glasses Containing Nanocrystallites of α-AgI. K.Nozaki, T.Itami: Journal of Physics - Condensed Matter, 2006, 18, 3617-27