This paper reports on the results of the investigations into the ionic conductivity and the effect of reduction in the percolation volume. It is demonstrated that the ionic conductivity of glasses in the Me n O m -P 2 O 5 -Li 2 O (Na 2 O) systems ( Me = W, Nb, Ti, Mo, V, Bi) is poorly correlated with the Li 2 O (Na 2 O) content and, in a number of cases, the dependence between these quantities is altogether absent. In the case when the ratio [Li 2 O]/[P 2 O 5 ] is used instead of the [Li 2 O] content as the argument, the data on the ionic conductivity σ for all the systems are approximated by the logarithmic dependences -log σ = f ([Li 2 O]/[P 2 O 5 ]) with a high degree of reliability. The ionic conductivity for the glasses under investigation, as for the (AgI) x -(AgPO 3 ) 1 -x superionic glasses, obeys the percolation law σ ~ ( y -y crit ) µ with the parameters y crit and µ close to those for the silvercontaining glasses but with y = [Li 2 O]/[P 2 O 5 ] instead of x for AgI. The observed dependences are explained within the Goodman strained mixed cluster model and two-dimensional percolation through the polar structural fragments containing Li + ions over the surface of an infinite percolation phosphate cluster reduced by Me n O m oxide in the glass volume.

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