Effects of Bi2O3 on DC conductivity and nonlinear optical properties of mixed ionic–electronic 98[20Li2O-xBi2O3-(80-x)TeO2]-2Ag glass system

98[20Li2O-xBi2O3-(80-x)TeO2]-2Ag glass system has been prepared using a melt-quenching method and characterized by impedance spectroscopy and optical absorption to study the effect of Bi2O3 substitution on DC conductivity and nonlinear optical properties of the glass samples. The nonlinear behavior of DC conductivity σDC showed an initial increase in σDC for x $$\le$$ 5 mol% before a large drop at x = 7 mol% due to blocking on Li+ ionic conduction which may be associated with mixed ionic–electronic (MIE) effect. The anomalous behavior of nonlinear refractive indices n2 and optical susceptibility χ3 with Bi2O3 substitution showed an initial increase at x   7 mol%. The minimum in n2 and χ3 were suggested to be due to the MIE effect that contributes to a reduction in polarization. On the other hand, optical basicity Λ initially increased for x < 7 mol% and dropped at x = 7 mol%, whereas an opposite trend was observed in interionic interaction parameter A. The decrease in Λ at x = 7 mol% indicated the decrease in oxygen donor character that reduces the ionic bonding in glass samples that may be attributed to MIE effect. Meanwhile, a steep increase in interionic interaction parameter A at x = 7 mol% indicated a reduction in unshared electron density between cation and anion pair, thereby promoting covalent bonding.